Future city design should meet the needs of the populace, animal populations, and native plant life. At the same time the design must be compatible with the local landscape and topography, aided by aerial photography and satellite images. City designers confer with ecologists to study the environment and assess the effects of urbanization on it today and tomorrow.
Mapping helps environmental scientists assess the size and dispersal of human populations, as well as the effects of human activities on the earth and the atmosphere. Today global maps describe the following conditions: atmospheric temperatures, ocean temperatures, surface water plant life, forest area and other vegetation, drought areas, population centers,
and light intensity. The National Geographic Society, for example, creates accurate maps by combining satellite images with information in databases on populations. The detailed maps show population densities, growth rates, family sizes, life expectancies, population movement patterns (immigration and emigration), and population age and gender.
High-resolution satellite images have been used for several years by law enforcement and census takers for estimating population size. Census workers begin by taking images of small blocks of a city and then counting the individual people in the block. They then compile block after block of data until they have calculated an entire region’s population size. Measurements like this make up part of a field of study known as population dynamics, which describes the major living and nonliving factors that cause increases, decreases, or other changes in the composition of a species, human or wildlife.
Of course, almost all of the components of human population dynamics impact biodiversity in some way. The growth and migration of human populations is the single biggest factor in pushing animals out of their habitat, destroying habitats, and causing extinction.Maps and images also provide information on the secondary effects of population dynamics on the environment. For instance, scientists use mapping to monitor the following by-products of climate change: coral reef bleaching, algal blooms (an overgrowth of algae in water due to pollution), phytoplankton levels, desertification, topsoil erosion, distribution of nonnative species, glacier regression, and melting of polar ice caps. Online maps generated by satellite imagery enable the public to find all the hazardous waste sites near them by typing in their zip code. Ecologists use this same technology to assess the wildlife populations most threatened by pollution. The Locus Technologies president, Neno Duplancic, explained
the future of environmental imaging in a 2008 interview to discuss his company’s technology: “Huge progress has been made over the past forty years. Back then, this industry did not exist. Today it makes headline news every day. . . . Our focus is information management. . . . The amount of environmental data has grown exponentially over the past decade and it will continue to rapidly increase with the emergence of real-time sensing and wireless transmission technologies.” As Duplancic suggests, environmental
science is entering a phase in which hardly an inch of the Earth has not been scrutinized.
Wednesday, July 25, 2012
Maintaining Migration Corridors
Migrations take place in the air, on land, and in the ocean. Of the 900 or so bird species living in North America, about 75 percent do some sort of migration; worldwide more than 1,000 species migrate. Several sandpiper species travel more than 8,000 miles (12,875 km) from the Arctic to the southern tip of South America, but the champion may be the Arctic tern, which flies more than 11,000 miles (17,703 km) from the Arctic Circle to the Antarctic Circle each breeding season, almost half Earth’s circumference. Other migrations extend a mere 500 miles; some songbirds migrate no more than a few miles or less each season. Migrating birds and any other species that must cover distance to find food, breed, or raise young contend with three main threats to life: exhaustion, lack of food, and predators.
Ocean migrations cover equally impressive distances. Gray whale migrations are the longest distance among mammals. The whales migrate between the Chukchi Sea off northern Alaska and Baja California in Mexico, about 12,000 miles (19,315 km).
Animal migrations have followed the same paths for centuries. Wildlife biologists do not know all the factors that influence the timing and the routes programmed into the genes of each migrating species, or how generations know to follow the exact same routes. In many cases, however, migrations take place for very practical reasons. African wildebeests, for
example, migrate in herds of more than one million animals every year in a constant search for fresh grazing land after their enormous numbers have depleted the local vegetation. Their migration follows a clockwise route more than 1,800 miles (2,900 km) over the Serengeti in Tanzania to Kenya’s Mara River. As the wildebeests travel, predator lions, cheetahs, and hyenas sustain their young by taking the herd’s unhealthy members.
Migration corridors like those of the wildebeest and the gray whale consist of a strip of land or sea through which the wildlife moves. Each migration corridor must contain a minimum amount of territory to provide sufficient food and protection from weather and predators. Because urban areas have encroached on the lands that create corridors, many migration routes now receive legal protection. In the United States, the Migratory Bird Treaty Act of 1918 bans the killing of migratory birds when they are flying or during their stopovers. The law protects grasslands and plains, coasts, river corridors, and forested areas that the birds
use along the migration route, called a flyway. The Endangered Species Act (1973) and the Marine Mammal Protection Act (1972) also outlaw the hunting of migrating animals. International cooperation provides a necessary help toward protecting migration corridors. For example, the International Ramsar Convention (Convention on Wetlands of International
Importance Especially as Waterfowl Habitats) of 1972 sets migratory bird treaties among the United States, Canada, and Japan. The United States also cooperates with Mexico for bird and mammal migration protection under the same law.
In the United States, government agencies and wildlife organizations have established joint programs for maintaining corridors. As an example, the Yellowstone to Yukon Conservation Initiative includes the work of more than 800 organizations in Canada and the United States to maintain a migration and habitat corridor extending from the Peel River in Canada’s northern Yukon Territory to the Wind River Valley in Wyoming. This corridor supports the migration patterns and breeding of grizzly bears, black bears, elk, wolves, mountain lions, plus many bird and fish species. The Yellowstone to Yukon Conservation Initiative explains the rationale for developing the corridor: “The Yellowstone to Yukon region is one of the last places left in the lower forty-eight [states] where the full historical suite of carnivores and ungulates—including grizzly bears and caribou—can still be found.” It goes on to say, “Addressing conservation on the large-landscape scale is revolutionary and timely. It’s no longer enough to preserve isolated forests, valleys, and wilderness areas. Connection
of habitats is key to the long-term health of ecosystems and the biological diversity that supports both wildlife and human communities.” There may be no better definition of ecology.
Urban habitat corridors serve similar purposes as they do in the natural environment. Migration corridors through urban areas help wildlife with
Ocean migrations cover equally impressive distances. Gray whale migrations are the longest distance among mammals. The whales migrate between the Chukchi Sea off northern Alaska and Baja California in Mexico, about 12,000 miles (19,315 km).
Animal migrations have followed the same paths for centuries. Wildlife biologists do not know all the factors that influence the timing and the routes programmed into the genes of each migrating species, or how generations know to follow the exact same routes. In many cases, however, migrations take place for very practical reasons. African wildebeests, for
example, migrate in herds of more than one million animals every year in a constant search for fresh grazing land after their enormous numbers have depleted the local vegetation. Their migration follows a clockwise route more than 1,800 miles (2,900 km) over the Serengeti in Tanzania to Kenya’s Mara River. As the wildebeests travel, predator lions, cheetahs, and hyenas sustain their young by taking the herd’s unhealthy members.
Migration corridors like those of the wildebeest and the gray whale consist of a strip of land or sea through which the wildlife moves. Each migration corridor must contain a minimum amount of territory to provide sufficient food and protection from weather and predators. Because urban areas have encroached on the lands that create corridors, many migration routes now receive legal protection. In the United States, the Migratory Bird Treaty Act of 1918 bans the killing of migratory birds when they are flying or during their stopovers. The law protects grasslands and plains, coasts, river corridors, and forested areas that the birds
use along the migration route, called a flyway. The Endangered Species Act (1973) and the Marine Mammal Protection Act (1972) also outlaw the hunting of migrating animals. International cooperation provides a necessary help toward protecting migration corridors. For example, the International Ramsar Convention (Convention on Wetlands of International
Importance Especially as Waterfowl Habitats) of 1972 sets migratory bird treaties among the United States, Canada, and Japan. The United States also cooperates with Mexico for bird and mammal migration protection under the same law.
In the United States, government agencies and wildlife organizations have established joint programs for maintaining corridors. As an example, the Yellowstone to Yukon Conservation Initiative includes the work of more than 800 organizations in Canada and the United States to maintain a migration and habitat corridor extending from the Peel River in Canada’s northern Yukon Territory to the Wind River Valley in Wyoming. This corridor supports the migration patterns and breeding of grizzly bears, black bears, elk, wolves, mountain lions, plus many bird and fish species. The Yellowstone to Yukon Conservation Initiative explains the rationale for developing the corridor: “The Yellowstone to Yukon region is one of the last places left in the lower forty-eight [states] where the full historical suite of carnivores and ungulates—including grizzly bears and caribou—can still be found.” It goes on to say, “Addressing conservation on the large-landscape scale is revolutionary and timely. It’s no longer enough to preserve isolated forests, valleys, and wilderness areas. Connection
of habitats is key to the long-term health of ecosystems and the biological diversity that supports both wildlife and human communities.” There may be no better definition of ecology.
Urban habitat corridors serve similar purposes as they do in the natural environment. Migration corridors through urban areas help wildlife with
The migration corridor that extends from the Canadian Rocky Mountains to Yellowstone National Park is called an ecoregion because it acts as an immense ecosystem spanning different climates and elevations and thousands of square miles. This migration corridor has been important in the reestablishment of grizzly bear and gray wolf populations.
the following: connecting fragmented habitats; escaping from floods and fires; escaping from predators; seeking new food sources; providing options for shelter, dens, and nests; providing rest stops for migrating birds; and avoiding construction, traffic, noise, and harassment from humans. corridors in cities. Traffic from urban sprawl has taken a toll on local biodiversity. In 2007 three rare Florida panthers died on roadways in a single week, because traffic does not discriminate between rare or abundant species, and these accidents kill mammals, birds, amphibians, reptiles, and even marine mammals that climb onto land and enter roadways.
Urban habitat corridors are usually of two kinds: riparian corridors along streams and rivers, and hard-surface corridors, hedgerows, tree lines, landscaping, or fencing. Sometimes people unintentionally build migration corridors, as they do when they plow roads in winter in Yellowstone National Park. Plowed roads allow greater access for snowcraft tours, snowmobiles, and snowshoeing, but the roads also enable the park’s bison
to roam farther in search of scarce food. The roads have helped weak animals because they no longer must expend energy pushing through snow
to roam farther in search of scarce food. The roads have helped weak animals because they no longer must expend energy pushing through snow
Habitats threatened by fragmentation can be helped by preserving corridors between
them. Habitat corridors allow isolated populations to find food and interbreed. The
best habitat corridors are protected by buffer zones that contain little or no human
interference.
them. Habitat corridors allow isolated populations to find food and interbreed. The
best habitat corridors are protected by buffer zones that contain little or no human
interference.
to find a few bites of grass. Once these animals wander outside Yellowstone, ranchers have shot them in fear the animals will transmit disease to their cattle. Migration corridors, therefore, must be built or maintained with a sound plan as to their effect on both humans and wildlife.
Fencing and other barriers prevent wildlife road losses, but at the same time these barriers halt migrations. Wide divided highways such as interstate highways also cause habitat fragmentation. Amy Masching, a conservation biologist at the Denver Zoological Foundation, explained to Audubon magazine in 2007, “Highways prevent species from accessing their historic migration and breeding areas, which reduces their genetic diversity.” For these reasons civil engineers have built landscaped bridges and tunnels in the United States, Canada, the Netherlands, and Australia. Structures have also been developed for large and small mammals, marsupials, birds, amphibians, and reptiles.
Species Adapted to Urban Life
Some species manage to adapt to urbanization even though their habitat is gone. Three different modes of adaptation allow some species to do quite well amid dense human populations. First, structural adaptive traits enable an animal to hide from predators. During London’s industrial revolution of the 1800s, as an example, resident peppered moths darkened from their normal light gray color so they could hide on soot-covered tree bark. This new coloring represented a structural adaptive trait. Second, species inherit physiological adaptive traits, for instance, black bears that invade campgrounds. Their
digestion has adapted to table scraps and fast-food leftovers, not at all the food they have evolved to eat! Third, behavioral adaptive traits are changes in an animal’s lifestyle to accommodate humans that have encroached into their environment. Raptors such as hawks, falcons, and ospreys have adapted to building nests on the sides of skyscrapers, under bridges, and atop light poles, and they fledge several new families each season.
In all cases in which species have adapted to urban life, the animals have done so because their genetic makeup enabled them to include one or more of the three adaptive traits: structural, physiological, or behavioral. Almost every animal that has adapted to urban life, furthermore, lives as a generalist rather than a specialist: rats, mice, raccoons, coyotes (now
living in New York City’s Central Park!), and many birds such as crows, starlings, house finches, and house sparrows.
Adaptation plays a critical part in species survival because animals have only three ways to respond to a change in their environment: adapt to the new conditions through natural selection, migrate to another area, or go extinct. The species most likely to go extinct are those that either cannot adapt quickly to changes brought by urbanization or cannot migrate
to a new, safer place. Even migrating animals sometimes find natural migration routes blocked by human activities and are then left only with urban wildlife protected areas such as preserves.
Aldo Leopold observed as early as 1933 the capacity of animals to adapt to human incursion into their habitat: “Lewis and Clarke found elk, deer, grizzly bear, and mountain sheep on the flat plains of Nebraska, a country very different from the mountain forests with which we now associate these species.” Fortunately for the species noted by these naturalists, the animals had been given enough time over generations to learn how to
find food and live at a different altitude than the Great Plains. Urbanization now occurs so fast, perhaps only human-made migration corridors can aid wildlife.
digestion has adapted to table scraps and fast-food leftovers, not at all the food they have evolved to eat! Third, behavioral adaptive traits are changes in an animal’s lifestyle to accommodate humans that have encroached into their environment. Raptors such as hawks, falcons, and ospreys have adapted to building nests on the sides of skyscrapers, under bridges, and atop light poles, and they fledge several new families each season.
In all cases in which species have adapted to urban life, the animals have done so because their genetic makeup enabled them to include one or more of the three adaptive traits: structural, physiological, or behavioral. Almost every animal that has adapted to urban life, furthermore, lives as a generalist rather than a specialist: rats, mice, raccoons, coyotes (now
living in New York City’s Central Park!), and many birds such as crows, starlings, house finches, and house sparrows.
Adaptation plays a critical part in species survival because animals have only three ways to respond to a change in their environment: adapt to the new conditions through natural selection, migrate to another area, or go extinct. The species most likely to go extinct are those that either cannot adapt quickly to changes brought by urbanization or cannot migrate
to a new, safer place. Even migrating animals sometimes find natural migration routes blocked by human activities and are then left only with urban wildlife protected areas such as preserves.
Aldo Leopold observed as early as 1933 the capacity of animals to adapt to human incursion into their habitat: “Lewis and Clarke found elk, deer, grizzly bear, and mountain sheep on the flat plains of Nebraska, a country very different from the mountain forests with which we now associate these species.” Fortunately for the species noted by these naturalists, the animals had been given enough time over generations to learn how to
find food and live at a different altitude than the Great Plains. Urbanization now occurs so fast, perhaps only human-made migration corridors can aid wildlife.
Succession
Habitat restoration requires a vibrant ecological succession to replace the natural plants and animals that once lived in a region. Ecological succession, or natural succession, consists of two components: primary succession and secondary succession. In primary succession, life establishes itself on an area that has little or no living things. Examples of primary succession are plants that grow on rock exposed by a receding glacier or on a cooled lava bed in the shadow of a volcano. Secondary succession comprises a series of related but different living communities replacing each other in sequence. For example, many valleys are actually prehistoric lakebeds that filled with eroded soils over thousands of years and
interfered with the lake’s aquatic plants. As the plants died, organic debris settled and decomposed and the lake became shallower, then the lake’s water evaporated and minerals formed a hard, flat surface. Finally, new bushes and weeds scratched out a living on the bleak, open plain. At some point in this progression, reptiles find this habitat to their liking, predators move in, and as new plants grow, additional species find food and habitat. As a result, a lush valley has replaced an ancient aquatic ecosystem.
Human-made structures also go through succession. These processes may take a hundred years or more but, in the end, a fortunate few places return to the conditions of an earlier time. The following hypothetical
Urban activities that repeatedly disrupt ecological successions force the animals living there to find new habitat continually. In time this stress may weaken a species’ population to the point of extinction.
interfered with the lake’s aquatic plants. As the plants died, organic debris settled and decomposed and the lake became shallower, then the lake’s water evaporated and minerals formed a hard, flat surface. Finally, new bushes and weeds scratched out a living on the bleak, open plain. At some point in this progression, reptiles find this habitat to their liking, predators move in, and as new plants grow, additional species find food and habitat. As a result, a lush valley has replaced an ancient aquatic ecosystem.
Human-made structures also go through succession. These processes may take a hundred years or more but, in the end, a fortunate few places return to the conditions of an earlier time. The following hypothetical
Ecological succession in plant life creates new ecosystems that develop over decades to centuries. As these ecosystems evolve from simple mosses to multispecies forests, animal populations also change and biodiversity develops. By returning land to nature, biodiversity eventually returns minus the species that have already gone extinct.
example describes situations in which plant and animal diversity changes and species adapt to the existing environment from one phase to the next.
- a woodland and meadow are cleared for settlers’ homesteads
- generations of descendants plant crops on the land
- small farms sell to a large agricultural producer that plants thousands of acres
- the agricultural company goes bankrupt and landowners buy small pieces to plant
- the landowners plant orchards
- the landowners convert the orchards to vineyards
- the vineyards are abandoned and left unattended
- plants and trees overgrow the vines
- a woodland reestablishes on the original land
Urban activities that repeatedly disrupt ecological successions force the animals living there to find new habitat continually. In time this stress may weaken a species’ population to the point of extinction.
History of Wildlife Preservation
Habitat is the environment, the physical place, where an organism normally lives. Put another way, a habitat is a species’ home. The following are examples of habitats: the Amazon jungle canopy, the African savanna, a North American coastline, an old-growth forest in the Pacific Northwest, and a salt marsh along the Chesapeake Bay. Urbanization has become a major cause of two of the biggest dangers to habitats like these: loss and fragmentation.
Habitat is lost, sometimes irreversibly, for a variety of reasons: development, urban expansion, destruction of agriculture, harvesting native plants, deforestation, invasion by exotic species, or pollution. Before the public became aware of the importance of habitat, many communities eliminated habitats thinking they had helped make the environment
healthier. Engineers drained swamps to eliminate disease, leveled woodlands to reduce fire hazard, dammed rivers to store water, and landscaped riparian areas as flood control. All of these activities once thought to be environmental improvements are now known to have contributed to the loss or near loss of thousands of plants and animals.
Habitat fragmentation is the breaking up of a large, continuous habitat into smaller, scattered pieces. Animals isolated in small, fragmented habitats may be more vulnerable to predators, disease, and competition with other species. In addition, if the fragments are far apart, many species are not able to traverse the urban areas in between. Small subpopulations then remain in isolated pockets, and in each one the genetic diversity decreases. Part of today’s ecological activities involves ways to save habitats, even in
places where urban communities surround them and divide them.
American naturalist Aldo Leopold proposed the idea of restoration ecology during his career with the U.S. Forest Service in the early 1900s. Throughout his career Leopold retained a special interest in techniques for managing and restoring wildlife populations. In 1933 he published his
theories on saving habitat in his book Game Management, which remains today a resource in restoration ecology. In another book by Leopold, 1972’s Round River, he wrote, “The government tells us we need flood control and comes to straighten the creek in our pasture. The engineer on the job tells us the creek is now able to carry off more flood water, but in the process we lost our old willows where the cows switched flies in the noon shade, and where the owl hooted on a winter night. We lost our little marshy spot where the fringed gentians bloomed. Some engineers are beginning to have a feeling in their bones that the meanderings of a creek not only improve the landscape but are a necessary part of the hydrologic functioning.” Leopold’s words describe the evolution of civil engineering into
today’s environmental engineering, which focuses on construction projects that work with nature rather than against it.
Today’s restoration ecologists begin a project by reviewing the living and nonliving components of a region to be restored. They then compile a thorough outline of the species natural to the area by using field studies data and define habitats with input from soil scientists, geologists, and climatologists.
Restoration often begins with fertilization of the soil to replace nutrients, followed by landscaping to induce either water drainage or water retention in ponds. Workers then plant native vegetation selected especially for the habitat. At the final phase, restoration teams leave the restored area and allow it to undergo natural ecological succession. This process consists of a sequence of changes in a community over time, the changes made up of various plant life and animal species that thrive in the habitat as it develops. For example, plant successions begin with bare rock and end with large, slow-growth trees. Between the start and the end, the succession progresses from small ground plants, then larger plants, then bushes, and then small, fast-growing trees. A natural succession left on its own restores ecosystems or habitats to almost their original condition.
Reconciliation ecology involves ways to share the Earth with other species even as humans continue to dominate in the habitat. Reconciliation ecology may also be referred to as habitat rehabilitation because some habitats in populated areas can no longer be returned to their original condition, but with good planning they can be made more available to animals. Reconciliation ecologists have their best chance of success when they start at the neighborhood level to save habitat, rather than trying to change an entire urban area. University of Arizona professor of ecolxviogy Michael Rosenzweig explained to the campus UA News, “Traditional conservation, which sets aside land, is a valuable practice that needs to continue, but there are limits to what it can do.” Examples of methods for returning habitat to nature through reconciliation ecology are the following:
they should avoid buying rare cacti, orchids, and exotic plants and trees, or wood and paper products derived from old-growth forests.
Ecological restoration takes much longer than reconciliation because it depends almost entirely on natural processes to rebuild components of the habitat. Reconciliation is faster because it alters the environment to mimic a habitat rather than rebuild it. Sometimes successful restoration or reconciliation becomes impossible because the habitat is too badly
ruined. In those cases environmental scientists turn to either ecosystem replacement or artificial ecosystems.
In ecosystem (or habitat) replacement, biologists replace a degraded ecosystem with another type of ecosystem that has a greater chance of sustaining native species. For example, a growing town may have destroyed a forest 50 years ago, but the same town can rehabilitate the area by creating a botanical park containing native vegetation. Artificial ecosystems consist of new constructed habitat rather than any attempt to restore the habitat
in cooperation with nature. A rebuilt wetland or a rebuilt coral reef offers an example of an artificial ecosystem (or habitat). Though artificial ecosystems sometimes bear little resemblance to the original habitat, many have proved to be successful places for native species to live. Coral reef scientist Thomas Goreau has explained the role of underwater metal structures as a substitute for damaged coral reefs: “Under these conditions, traditional [revival] methods fail. Our method is the only one that speeds coral growth.” But the Nature Conservancy’s coral reef expert Rod Salm shared with the Associated Press in 2007 his opposing view on the limited value of artificial reefs: “The extent of [coral] bleaching . . . is just too big. The scale is enormous and the cost prohibitive.” Perhaps artificial habitat
will serve as one of many ways to help species from going extinct, but science cannot depend on any single method to save endangered animals.
Habitat is lost, sometimes irreversibly, for a variety of reasons: development, urban expansion, destruction of agriculture, harvesting native plants, deforestation, invasion by exotic species, or pollution. Before the public became aware of the importance of habitat, many communities eliminated habitats thinking they had helped make the environment
healthier. Engineers drained swamps to eliminate disease, leveled woodlands to reduce fire hazard, dammed rivers to store water, and landscaped riparian areas as flood control. All of these activities once thought to be environmental improvements are now known to have contributed to the loss or near loss of thousands of plants and animals.
Habitat fragmentation is the breaking up of a large, continuous habitat into smaller, scattered pieces. Animals isolated in small, fragmented habitats may be more vulnerable to predators, disease, and competition with other species. In addition, if the fragments are far apart, many species are not able to traverse the urban areas in between. Small subpopulations then remain in isolated pockets, and in each one the genetic diversity decreases. Part of today’s ecological activities involves ways to save habitats, even in
places where urban communities surround them and divide them.
American naturalist Aldo Leopold proposed the idea of restoration ecology during his career with the U.S. Forest Service in the early 1900s. Throughout his career Leopold retained a special interest in techniques for managing and restoring wildlife populations. In 1933 he published his
theories on saving habitat in his book Game Management, which remains today a resource in restoration ecology. In another book by Leopold, 1972’s Round River, he wrote, “The government tells us we need flood control and comes to straighten the creek in our pasture. The engineer on the job tells us the creek is now able to carry off more flood water, but in the process we lost our old willows where the cows switched flies in the noon shade, and where the owl hooted on a winter night. We lost our little marshy spot where the fringed gentians bloomed. Some engineers are beginning to have a feeling in their bones that the meanderings of a creek not only improve the landscape but are a necessary part of the hydrologic functioning.” Leopold’s words describe the evolution of civil engineering into
today’s environmental engineering, which focuses on construction projects that work with nature rather than against it.
Today’s restoration ecologists begin a project by reviewing the living and nonliving components of a region to be restored. They then compile a thorough outline of the species natural to the area by using field studies data and define habitats with input from soil scientists, geologists, and climatologists.
Restoration often begins with fertilization of the soil to replace nutrients, followed by landscaping to induce either water drainage or water retention in ponds. Workers then plant native vegetation selected especially for the habitat. At the final phase, restoration teams leave the restored area and allow it to undergo natural ecological succession. This process consists of a sequence of changes in a community over time, the changes made up of various plant life and animal species that thrive in the habitat as it develops. For example, plant successions begin with bare rock and end with large, slow-growth trees. Between the start and the end, the succession progresses from small ground plants, then larger plants, then bushes, and then small, fast-growing trees. A natural succession left on its own restores ecosystems or habitats to almost their original condition.
Reconciliation ecology involves ways to share the Earth with other species even as humans continue to dominate in the habitat. Reconciliation ecology may also be referred to as habitat rehabilitation because some habitats in populated areas can no longer be returned to their original condition, but with good planning they can be made more available to animals. Reconciliation ecologists have their best chance of success when they start at the neighborhood level to save habitat, rather than trying to change an entire urban area. University of Arizona professor of ecolxviogy Michael Rosenzweig explained to the campus UA News, “Traditional conservation, which sets aside land, is a valuable practice that needs to continue, but there are limits to what it can do.” Examples of methods for returning habitat to nature through reconciliation ecology are the following:
- planting bushes and trees that attract birds and butterflies
- constructing birdhouses and bat boxes
- landscaping yards to provide food and a water source for indigenous mammals
- replacing lawns with natural, local plant species
- relandscaping golf courses and cemeteries to contain biologically diverse vegetation
- leaving dead trees in woodlands to provide nesting cavities
- planning urban parks around riparian areas
- constructing migration corridors near or though urban areas
they should avoid buying rare cacti, orchids, and exotic plants and trees, or wood and paper products derived from old-growth forests.
Ecological restoration takes much longer than reconciliation because it depends almost entirely on natural processes to rebuild components of the habitat. Reconciliation is faster because it alters the environment to mimic a habitat rather than rebuild it. Sometimes successful restoration or reconciliation becomes impossible because the habitat is too badly
ruined. In those cases environmental scientists turn to either ecosystem replacement or artificial ecosystems.
In ecosystem (or habitat) replacement, biologists replace a degraded ecosystem with another type of ecosystem that has a greater chance of sustaining native species. For example, a growing town may have destroyed a forest 50 years ago, but the same town can rehabilitate the area by creating a botanical park containing native vegetation. Artificial ecosystems consist of new constructed habitat rather than any attempt to restore the habitat
in cooperation with nature. A rebuilt wetland or a rebuilt coral reef offers an example of an artificial ecosystem (or habitat). Though artificial ecosystems sometimes bear little resemblance to the original habitat, many have proved to be successful places for native species to live. Coral reef scientist Thomas Goreau has explained the role of underwater metal structures as a substitute for damaged coral reefs: “Under these conditions, traditional [revival] methods fail. Our method is the only one that speeds coral growth.” But the Nature Conservancy’s coral reef expert Rod Salm shared with the Associated Press in 2007 his opposing view on the limited value of artificial reefs: “The extent of [coral] bleaching . . . is just too big. The scale is enormous and the cost prohibitive.” Perhaps artificial habitat
will serve as one of many ways to help species from going extinct, but science cannot depend on any single method to save endangered animals.
Monday, July 9, 2012
Monitoring and Mapping the Environment
Future city design should meet the needs of the populace, animal populations, and native plant life. At the same time the design must be compatible with the local landscape and topography, aided by aerial photography and satellite images. City designers confer with ecologists to study the environment and assess the effects of urbanization on it today and tomorrow.
Mapping helps environmental scientists assess the size and dispersal of human populations, as well as the effects of human activities on the earth and the atmosphere. Today global maps describe the following conditions: atmospheric temperatures, ocean temperatures, surface water plant life, forest area and other vegetation, drought areas, population centers, and light intensity. The National Geographic Society, for example, creates accurate maps by combining satellite images with information in databases on populations. The detailed maps show population densities, growth rates, family sizes, life expectancies, population movement patterns (immigration and emigration), and population age and gender.
High-resolution satellite images have been used for several years by law enforcement and census takers for estimating population size. Census workers begin by taking images of small blocks of a city and then counting the individual people in the block. They then compile block after block of data until they have calculated an entire region’s population size. Measurements like this make up part of a field of study known as population dynamics, which describes the major living and nonliving factors that cause increases, decreases, or other changes in the composition of a species, human or wildlife.
Of course, almost all of the components of human population dynamics impact biodiversity in some way. The growth and migration of human populations is the single biggest factor in pushing animals out of their habitat, destroying habitats, and causing extinction. Maps and images also provide information on the secondary effects of population dynamics on the environment. For instance, scientists use mapping to monitor the following by-products of climate change: coral reef bleaching, algal blooms (an overgrowth of algae in water due to pollution), phytoplankton levels, desertification, topsoil erosion, distribution of nonnative species, glacier regression, and melting of polar ice caps. Online maps generated by satellite imagery enable the public to find all the hazardous waste sites near them by typing in their zip code. Ecologists use this same technology to assess the wildlife populations most threatened by pollution. The Locus Technologies president, Neno Duplancic, explained the future of environmental imaging in a 2008 interview to discuss his company’s technology: “Huge progress has been made over the past forty years. Back then, this industry did not exist. Today it makes headline news every day. . . . Our focus is information management. . . . The amount of environmental data has grown exponentially over the past decade and it will continue to rapidly increase with the emergence of real-time sensing and wireless transmission technologies.” As Duplancic suggests, environmental
science is entering a phase in which hardly an inch of the Earth has not been scrutinized.
Mapping helps environmental scientists assess the size and dispersal of human populations, as well as the effects of human activities on the earth and the atmosphere. Today global maps describe the following conditions: atmospheric temperatures, ocean temperatures, surface water plant life, forest area and other vegetation, drought areas, population centers, and light intensity. The National Geographic Society, for example, creates accurate maps by combining satellite images with information in databases on populations. The detailed maps show population densities, growth rates, family sizes, life expectancies, population movement patterns (immigration and emigration), and population age and gender.
High-resolution satellite images have been used for several years by law enforcement and census takers for estimating population size. Census workers begin by taking images of small blocks of a city and then counting the individual people in the block. They then compile block after block of data until they have calculated an entire region’s population size. Measurements like this make up part of a field of study known as population dynamics, which describes the major living and nonliving factors that cause increases, decreases, or other changes in the composition of a species, human or wildlife.
Of course, almost all of the components of human population dynamics impact biodiversity in some way. The growth and migration of human populations is the single biggest factor in pushing animals out of their habitat, destroying habitats, and causing extinction. Maps and images also provide information on the secondary effects of population dynamics on the environment. For instance, scientists use mapping to monitor the following by-products of climate change: coral reef bleaching, algal blooms (an overgrowth of algae in water due to pollution), phytoplankton levels, desertification, topsoil erosion, distribution of nonnative species, glacier regression, and melting of polar ice caps. Online maps generated by satellite imagery enable the public to find all the hazardous waste sites near them by typing in their zip code. Ecologists use this same technology to assess the wildlife populations most threatened by pollution. The Locus Technologies president, Neno Duplancic, explained the future of environmental imaging in a 2008 interview to discuss his company’s technology: “Huge progress has been made over the past forty years. Back then, this industry did not exist. Today it makes headline news every day. . . . Our focus is information management. . . . The amount of environmental data has grown exponentially over the past decade and it will continue to rapidly increase with the emergence of real-time sensing and wireless transmission technologies.” As Duplancic suggests, environmental
science is entering a phase in which hardly an inch of the Earth has not been scrutinized.
Maintaining Migration Corridors
Migrations take place in the air, on land, and in the ocean. Of the 900 or so bird species living in North America, about 75 percent do some sort of migration; worldwide more than 1,000 species migrate. Several sandpiper species travel more than 8,000 miles (12,875 km) from the Arctic to the southern tip of South America, but the champion may be the Arctic tern, which flies more than 11,000 miles (17,703 km) from the Arctic Circle to the Antarctic Circle each breeding season, almost half Earth’s circumference. Other migrations extend a mere 500 miles; some songbirds migrate no more than a few miles or less each season. Migrating birds and any other species that must cover distance to find food, breed, or raise young contend with three main threats to life: exhaustion, lack of food, and predators. Ocean migrations cover equally impressive distances. Gray whale migrations are the longest distance among mammals. The whales migrate between the Chukchi Sea off northern Alaska and Baja California in Mexico, about 12,000 miles (19,315 km).
Animal migrations have followed the same paths for centuries. Wildlife biologists do not know all the factors that influence the timing and the routes programmed into the genes of each migrating species, or how generations know to follow the exact same routes. In many cases, however, migrations take place for very practical reasons. African wildebeests, for example, migrate in herds of more than one million animals every year in a constant search for fresh grazing land after their enormous numbers have depleted the local vegetation. Their migration follows a clockwise route more than 1,800 miles (2,900 km) over the Serengeti in Tanzania to Kenya’s Mara River. As the wildebeests travel, predator lions, cheetahs, and hyenas sustain their young by taking the herd’s unhealthy members.
Migration corridors like those of the wildebeest and the gray whale consist of a strip of land or sea through which the wildlife moves. Each migration corridor must contain a minimum amount of territory to provide sufficient food and protection from weather and predators. Because urban areas have encroached on the lands that create corridors, many migration routes now receive legal protection. In the United States, the Migratory Bird Treaty Act of 1918 bans the killing of migratory birds when they are flying or during their stopovers. The law protects grasslands
and plains, coasts, river corridors, and forested areas that the birds use along the migration route, called a flyway. The Endangered Species Act (1973) and the Marine Mammal Protection Act (1972) also outlaw the hunting of migrating animals. International cooperation provides a necessary help toward protecting migration corridors. For example, the International Ramsar Convention (Convention on Wetlands of International Importance Especially as Waterfowl Habitats) of 1972 sets migratory bird treaties among the United States, Canada, and Japan. The United States also cooperates with Mexico for bird and mammal migration protection under the same law.
In the United States, government agencies and wildlife organizations have established joint programs for maintaining corridors. As an example, the Yellowstone to Yukon Conservation Initiative includes the work of more than 800 organizations in Canada and the United States to maintain a migration and habitat corridor extending from the Peel River in Canada’s northern Yukon Territory to the Wind River Valley in Wyoming. This corridor supports the migration patterns and breeding of grizzly bears, black bears, elk, wolves, mountain lions, plus many bird and fish species. The Yellowstone to Yukon Conservation Initiative explains the rationale for developing the corridor: “The Yellowstone to Yukon region is one of the last places left in the lower forty-eight [states] where the full historical suite of carnivores and ungulates—including grizzly bears and caribou—can still be found.” It goes on to say, “Addressing conservation on the large-landscape scale is revolutionary and timely. It’s no longer enough to preserve isolated forests, valleys, and wilderness areas. Connection of habitats is key to the long-term health of ecosystems and the biological diversity that supports both wildlife and human communities.” There may be no better definition of ecology.
Urban habitat corridors serve similar purposes as they do in the natural environment. Migration corridors through urban areas help wildlife with
The migration corridor that extends from the Canadian Rocky Mountains to Yellowstone National Park is called an ecoregion because it acts as an immense ecosystem spanning different climates and elevations and thousands of square miles. This migration corridor has been important in the reestablishment of grizzly bear and gray wolf populations.
the following: connecting fragmented habitats; escaping from floods and fires; escaping from predators; seeking new food sources; providing options for shelter, dens, and nests; providing rest stops for migrating birds; and avoiding construction, traffic, noise, and harassment from humans. corridors in cities. Traffic from urban sprawl has taken a toll on local biodiversity. In 2007 three rare Florida panthers died on roadways in a single week, because traffic does not discriminate between rare or abundant species, and these accidents kill mammals, birds, amphibians, reptiles, and even marine mammals that climb onto land and enter roadways.
Urban habitat corridors are usually of two kinds: riparian corridors along streams and rivers, and hard-surface corridors, hedgerows, tree lines, landscaping, or fencing. Sometimes people unintentionally build migration corridors, as they do when they plow roads in winter in Yellowstone National Park. Plowed roads allow greater access for snowcraft tours, snowmobiles, and snowshoeing, but the roads also enable the park’s bison to roam farther in search of scarce food. The roads have helped weak animals because they no longer must expend energy pushing through snow
Habitats threatened by fragmentation can be helped by preserving corridors between them. Habitat corridors allow isolated populations to find food and interbreed. The best habitat corridors are protected by buffer zones that contain little or no human interference.
to find a few bites of grass. Once these animals wander outside Yellowstone, ranchers have shot them in fear the animals will transmit disease to their cattle. Migration corridors, therefore, must be built or maintained with a sound plan as to their effect on both humans and wildlife.
Fencing and other barriers prevent wildlife road losses, but at the same time these barriers halt migrations. Wide divided highways such as interstate highways also cause habitat fragmentation. Amy Masching, a conservation biologist at the Denver Zoological Foundation, explained to Audubon magazine in 2007, “Highways prevent species from accessing their historic migration and breeding areas, which reduces their genetic diversity.” For these reasons civil engineers have built landscaped bridges and tunnels in the United States, Canada, the Netherlands, and Australia. Structures have also been developed for large and small mammals, marsupials, birds, amphibians, and reptiles.
Animal migrations have followed the same paths for centuries. Wildlife biologists do not know all the factors that influence the timing and the routes programmed into the genes of each migrating species, or how generations know to follow the exact same routes. In many cases, however, migrations take place for very practical reasons. African wildebeests, for example, migrate in herds of more than one million animals every year in a constant search for fresh grazing land after their enormous numbers have depleted the local vegetation. Their migration follows a clockwise route more than 1,800 miles (2,900 km) over the Serengeti in Tanzania to Kenya’s Mara River. As the wildebeests travel, predator lions, cheetahs, and hyenas sustain their young by taking the herd’s unhealthy members.
Migration corridors like those of the wildebeest and the gray whale consist of a strip of land or sea through which the wildlife moves. Each migration corridor must contain a minimum amount of territory to provide sufficient food and protection from weather and predators. Because urban areas have encroached on the lands that create corridors, many migration routes now receive legal protection. In the United States, the Migratory Bird Treaty Act of 1918 bans the killing of migratory birds when they are flying or during their stopovers. The law protects grasslands
and plains, coasts, river corridors, and forested areas that the birds use along the migration route, called a flyway. The Endangered Species Act (1973) and the Marine Mammal Protection Act (1972) also outlaw the hunting of migrating animals. International cooperation provides a necessary help toward protecting migration corridors. For example, the International Ramsar Convention (Convention on Wetlands of International Importance Especially as Waterfowl Habitats) of 1972 sets migratory bird treaties among the United States, Canada, and Japan. The United States also cooperates with Mexico for bird and mammal migration protection under the same law.
In the United States, government agencies and wildlife organizations have established joint programs for maintaining corridors. As an example, the Yellowstone to Yukon Conservation Initiative includes the work of more than 800 organizations in Canada and the United States to maintain a migration and habitat corridor extending from the Peel River in Canada’s northern Yukon Territory to the Wind River Valley in Wyoming. This corridor supports the migration patterns and breeding of grizzly bears, black bears, elk, wolves, mountain lions, plus many bird and fish species. The Yellowstone to Yukon Conservation Initiative explains the rationale for developing the corridor: “The Yellowstone to Yukon region is one of the last places left in the lower forty-eight [states] where the full historical suite of carnivores and ungulates—including grizzly bears and caribou—can still be found.” It goes on to say, “Addressing conservation on the large-landscape scale is revolutionary and timely. It’s no longer enough to preserve isolated forests, valleys, and wilderness areas. Connection of habitats is key to the long-term health of ecosystems and the biological diversity that supports both wildlife and human communities.” There may be no better definition of ecology.
Urban habitat corridors serve similar purposes as they do in the natural environment. Migration corridors through urban areas help wildlife with
The migration corridor that extends from the Canadian Rocky Mountains to Yellowstone National Park is called an ecoregion because it acts as an immense ecosystem spanning different climates and elevations and thousands of square miles. This migration corridor has been important in the reestablishment of grizzly bear and gray wolf populations.
the following: connecting fragmented habitats; escaping from floods and fires; escaping from predators; seeking new food sources; providing options for shelter, dens, and nests; providing rest stops for migrating birds; and avoiding construction, traffic, noise, and harassment from humans. corridors in cities. Traffic from urban sprawl has taken a toll on local biodiversity. In 2007 three rare Florida panthers died on roadways in a single week, because traffic does not discriminate between rare or abundant species, and these accidents kill mammals, birds, amphibians, reptiles, and even marine mammals that climb onto land and enter roadways.
Urban habitat corridors are usually of two kinds: riparian corridors along streams and rivers, and hard-surface corridors, hedgerows, tree lines, landscaping, or fencing. Sometimes people unintentionally build migration corridors, as they do when they plow roads in winter in Yellowstone National Park. Plowed roads allow greater access for snowcraft tours, snowmobiles, and snowshoeing, but the roads also enable the park’s bison to roam farther in search of scarce food. The roads have helped weak animals because they no longer must expend energy pushing through snow
Habitats threatened by fragmentation can be helped by preserving corridors between them. Habitat corridors allow isolated populations to find food and interbreed. The best habitat corridors are protected by buffer zones that contain little or no human interference.
to find a few bites of grass. Once these animals wander outside Yellowstone, ranchers have shot them in fear the animals will transmit disease to their cattle. Migration corridors, therefore, must be built or maintained with a sound plan as to their effect on both humans and wildlife.
Fencing and other barriers prevent wildlife road losses, but at the same time these barriers halt migrations. Wide divided highways such as interstate highways also cause habitat fragmentation. Amy Masching, a conservation biologist at the Denver Zoological Foundation, explained to Audubon magazine in 2007, “Highways prevent species from accessing their historic migration and breeding areas, which reduces their genetic diversity.” For these reasons civil engineers have built landscaped bridges and tunnels in the United States, Canada, the Netherlands, and Australia. Structures have also been developed for large and small mammals, marsupials, birds, amphibians, and reptiles.
Species Adapted to Urban Life
Some species manage to adapt to urbanization even though their habitat is gone. Three different modes of adaptation allow some species to do quite well amid dense human populations. First, structural adaptive traits enable an animal to hide from predators. During London’s industrial revolution of the 1800s, as an example, resident peppered moths darkened from their normal light gray color so they could hide on soot-covered tree bark. This new coloring represented a structural adaptive trait. Second, species inherit physiological adaptive traits, for instance, black bears that invade campgrounds. Their digestion has adapted to table scraps and fast-food leftovers, not at all the food they have evolved to eat! Third, behavioral adaptive traits are changes in an animal’s lifestyle to accommodate humans that have encroached into their environment. Raptors such as hawks, falcons, and ospreys have adapted to building nests on the sides of skyscrapers, under bridges, and atop light poles, and they fledge several new families each season.
In all cases in which species have adapted to urban life, the animals have done so because their genetic makeup enabled them to include one or more of the three adaptive traits: structural, physiological, or behavioral. Almost every animal that has adapted to urban life, furthermore, lives as a generalist rather than a specialist: rats, mice, raccoons, coyotes (now living in New York City’s Central Park!), and many birds such as crows, starlings, house finches, and house sparrows.
Adaptation plays a critical part in species survival because animals have only three ways to respond to a change in their environment: adapt to the new conditions through natural selection, migrate to another area, or go extinct. The species most likely to go extinct are those that either cannot adapt quickly to changes brought by urbanization or cannot migrate to a new, safer place. Even migrating animals sometimes find natural migration routes blocked by human activities and are then left only with urban wildlife protected areas such as preserves.
Aldo Leopold observed as early as 1933 the capacity of animals to adapt to human incursion into their habitat: “Lewis and Clarke found elk, deer, grizzly bear, and mountain sheep on the flat plains of Nebraska, a country very different from the mountain forests with which we now associate these species.” Fortunately for the species noted by these naturalists, the animals had been given enough time over generations to learn how to find food and live at a different altitude than the Great Plains. Urbanization now occurs so fast, perhaps only human-made migration corridors can aid wildlife.
In all cases in which species have adapted to urban life, the animals have done so because their genetic makeup enabled them to include one or more of the three adaptive traits: structural, physiological, or behavioral. Almost every animal that has adapted to urban life, furthermore, lives as a generalist rather than a specialist: rats, mice, raccoons, coyotes (now living in New York City’s Central Park!), and many birds such as crows, starlings, house finches, and house sparrows.
Adaptation plays a critical part in species survival because animals have only three ways to respond to a change in their environment: adapt to the new conditions through natural selection, migrate to another area, or go extinct. The species most likely to go extinct are those that either cannot adapt quickly to changes brought by urbanization or cannot migrate to a new, safer place. Even migrating animals sometimes find natural migration routes blocked by human activities and are then left only with urban wildlife protected areas such as preserves.
Aldo Leopold observed as early as 1933 the capacity of animals to adapt to human incursion into their habitat: “Lewis and Clarke found elk, deer, grizzly bear, and mountain sheep on the flat plains of Nebraska, a country very different from the mountain forests with which we now associate these species.” Fortunately for the species noted by these naturalists, the animals had been given enough time over generations to learn how to find food and live at a different altitude than the Great Plains. Urbanization now occurs so fast, perhaps only human-made migration corridors can aid wildlife.
Succession
Habitat restoration requires a vibrant ecological succession to replace the natural plants and animals that once lived in a region. Ecological succession, or natural succession, consists of two components: primary succession and secondary succession. In primary succession, life establishes itself on an area that has little or no living things. Examples of primary succession are plants that grow on rock exposed by a receding glacier or on a cooled lava bed in the shadow of a volcano. Secondary succession comprises a series of related but different living communities replacing each other in sequence. For example, many valleys are actually prehistoric lakebeds that filled with eroded soils over thousands of years and interfered with the lake’s aquatic plants. As the plants died, organic debris settled and decomposed and the lake became shallower, then the lake’s water evaporated and minerals formed a hard, flat surface. Finally, new bushes and weeds scratched out a living on the bleak, open plain. At some point in this progression, reptiles find this habitat to their liking, predators move in, and as new plants grow, additional species find food and habitat. As a result, a lush valley has replaced an ancient aquatic ecosystem.
Human-made structures also go through succession. These processes may take a hundred years or more but, in the end, a fortunate few places return to the conditions of an earlier time. The following hypothetical
Ecological succession in plant life creates new ecosystems that develop over decades to centuries. As these ecosystems evolve from simple mosses to multispecies forests, animal populations also change and biodiversity develops. By returning land to nature, biodiversity eventually returns minus the species that have already gone extinct.
example describes situations in which plant and animal diversity changes and species adapt to the existing environment from one phase to the next.
Human-made structures also go through succession. These processes may take a hundred years or more but, in the end, a fortunate few places return to the conditions of an earlier time. The following hypothetical
Ecological succession in plant life creates new ecosystems that develop over decades to centuries. As these ecosystems evolve from simple mosses to multispecies forests, animal populations also change and biodiversity develops. By returning land to nature, biodiversity eventually returns minus the species that have already gone extinct.
example describes situations in which plant and animal diversity changes and species adapt to the existing environment from one phase to the next.
- a woodland and meadow are cleared for settlers’ homesteads
- generations of descendants plant crops on the land
- small farms sell to a large agricultural producer that plants thousands of acres
- the agricultural company goes bankrupt and landowners buy small pieces to plant
- the landowners plant orchards
- the landowners convert the orchards to vineyards
- the vineyards are abandoned and left unattended
- plants and trees overgrow the vines
- a woodland reestablishes on the original land
Actions such as clear-cutting forests, plowing meadows, establishing ranch lands, or planting grasslands with agricultural crops disrupt natural succession. Some activities cause succession to go backward to a previous phase. For instance, a controlled fire that clears part of a forest exposes bare rock and leaves only small ground-covering plants. This means the ecological
succession must begin again from that point to rebuild the forest.
Urban activities that repeatedly disrupt ecological successions force the animals living there to find new habitat continually. In time this stress may weaken a species’ population to the point of extinction.
Sunday, July 8, 2012
Habitat Loss and Fragmentation
Habitat is the environment, the physical place, where an organism normally lives. Put another way, a habitat is a species’ home. The following are examples of habitats: the Amazon jungle canopy, the African savanna, a North American coastline, an old-growth forest in the Pacific Northwest, and a salt marsh along the Chesapeake Bay. Urbanization has become a major cause of two of the biggest dangers to habitats like these: loss and fragmentation.
Habitat is lost, sometimes irreversibly, for a variety of reasons: development, urban expansion, destruction of agriculture, harvesting native plants, deforestation, invasion by exotic species, or pollution. Before the public became aware of the importance of habitat, many communities eliminated habitats thinking they had helped make the environment healthier. Engineers drained swamps to eliminate disease, leveled woodlands to reduce fire hazard, dammed rivers to store water, and landscaped riparian areas as flood control. All of these activities once thought to be environmental improvements are now known to have contributed to the loss or near loss of thousands of plants and animals.
Habitat fragmentation is the breaking up of a large, continuous habitat into smaller, scattered pieces. Animals isolated in small, fragmented habitats may be more vulnerable to predators, disease, and competition with other species. In addition, if the fragments are far apart, many species are not able to traverse the urban areas in between. Small subpopulations then remain in isolated pockets, and in each one the genetic diversity decreases. Part of today’s ecological activities involves ways to save habitats, even in places where urban communities surround them and divide them.
American naturalist Aldo Leopold proposed the idea of restoration ecology during his career with the U.S. Forest Service in the early 1900s. Throughout his career Leopold retained a special interest in techniques for managing and restoring wildlife populations. In 1933 he published his
theories on saving habitat in his book Game Management, which remains today a resource in restoration ecology. In another book by Leopold, 1972’s Round River, he wrote, “The government tells us we need flood control and comes to straighten the creek in our pasture. The engineer on the job tells us the creek is now able to carry off more flood water, but in the process we lost our old willows where the cows switched flies in the noon shade, and where the owl hooted on a winter night. We lost our little marshy spot where the fringed gentians bloomed. Some engineers are beginning to have a feeling in their bones that the meanderings of a creek not only improve the landscape but are a necessary part of the hydrologic functioning.” Leopold’s words describe the evolution of civil engineering into today’s environmental engineering, which focuses on construction projects that work with nature rather than against it.
Today’s restoration ecologists begin a project by reviewing the living and nonliving components of a region to be restored. They then compile a thorough outline of the species natural to the area by using field studies data and define habitats with input from soil scientists, geologists, and climatologists.
Restoration often begins with fertilization of the soil to replace nutrients, followed by landscaping to induce either water drainage or water retention in ponds. Workers then plant native vegetation selected especially for the habitat. At the final phase, restoration teams leave the restored area and allow it to undergo natural ecological succession. This process consists of a sequence of changes in a community over time, the changes made up of various plant life and animal species that thrive in the habitat as it develops. For example, plant successions begin with bare rock and end with large, slow-growth trees. Between the start and the end, the succession progresses from small ground plants, then larger plants, then bushes, and then small, fast-growing trees. A natural succession left on its own restores ecosystems or habitats to almost their original condition.
Reconciliation ecology involves ways to share the Earth with other species even as humans continue to dominate in the habitat. Reconciliation ecology may also be referred to as habitat rehabilitation because some habitats in populated areas can no longer be returned to their original condition, but with good planning they can be made more available to animals. Reconciliation ecologists have their best chance of success when they start at the neighborhood level to save habitat, rather than trying to change an entire urban area. University of Arizona professor of ecolxviogy Michael Rosenzweig explained to the campus UA News, “Traditional conservation, which sets aside land, is a valuable practice that needs to continue, but there are limits to what it can do.” Examples of methods for returning habitat to nature through reconciliation ecology are the following:
Habitat is lost, sometimes irreversibly, for a variety of reasons: development, urban expansion, destruction of agriculture, harvesting native plants, deforestation, invasion by exotic species, or pollution. Before the public became aware of the importance of habitat, many communities eliminated habitats thinking they had helped make the environment healthier. Engineers drained swamps to eliminate disease, leveled woodlands to reduce fire hazard, dammed rivers to store water, and landscaped riparian areas as flood control. All of these activities once thought to be environmental improvements are now known to have contributed to the loss or near loss of thousands of plants and animals.
Habitat fragmentation is the breaking up of a large, continuous habitat into smaller, scattered pieces. Animals isolated in small, fragmented habitats may be more vulnerable to predators, disease, and competition with other species. In addition, if the fragments are far apart, many species are not able to traverse the urban areas in between. Small subpopulations then remain in isolated pockets, and in each one the genetic diversity decreases. Part of today’s ecological activities involves ways to save habitats, even in places where urban communities surround them and divide them.
American naturalist Aldo Leopold proposed the idea of restoration ecology during his career with the U.S. Forest Service in the early 1900s. Throughout his career Leopold retained a special interest in techniques for managing and restoring wildlife populations. In 1933 he published his
theories on saving habitat in his book Game Management, which remains today a resource in restoration ecology. In another book by Leopold, 1972’s Round River, he wrote, “The government tells us we need flood control and comes to straighten the creek in our pasture. The engineer on the job tells us the creek is now able to carry off more flood water, but in the process we lost our old willows where the cows switched flies in the noon shade, and where the owl hooted on a winter night. We lost our little marshy spot where the fringed gentians bloomed. Some engineers are beginning to have a feeling in their bones that the meanderings of a creek not only improve the landscape but are a necessary part of the hydrologic functioning.” Leopold’s words describe the evolution of civil engineering into today’s environmental engineering, which focuses on construction projects that work with nature rather than against it.Today’s restoration ecologists begin a project by reviewing the living and nonliving components of a region to be restored. They then compile a thorough outline of the species natural to the area by using field studies data and define habitats with input from soil scientists, geologists, and climatologists.
Restoration often begins with fertilization of the soil to replace nutrients, followed by landscaping to induce either water drainage or water retention in ponds. Workers then plant native vegetation selected especially for the habitat. At the final phase, restoration teams leave the restored area and allow it to undergo natural ecological succession. This process consists of a sequence of changes in a community over time, the changes made up of various plant life and animal species that thrive in the habitat as it develops. For example, plant successions begin with bare rock and end with large, slow-growth trees. Between the start and the end, the succession progresses from small ground plants, then larger plants, then bushes, and then small, fast-growing trees. A natural succession left on its own restores ecosystems or habitats to almost their original condition.
Reconciliation ecology involves ways to share the Earth with other species even as humans continue to dominate in the habitat. Reconciliation ecology may also be referred to as habitat rehabilitation because some habitats in populated areas can no longer be returned to their original condition, but with good planning they can be made more available to animals. Reconciliation ecologists have their best chance of success when they start at the neighborhood level to save habitat, rather than trying to change an entire urban area. University of Arizona professor of ecolxviogy Michael Rosenzweig explained to the campus UA News, “Traditional conservation, which sets aside land, is a valuable practice that needs to continue, but there are limits to what it can do.” Examples of methods for returning habitat to nature through reconciliation ecology are the following:
- planting bushes and trees that attract birds and butterflies
- constructing birdhouses and bat boxes
- landscaping yards to provide food and a water source for indigenous mammals
- replacing lawns with natural, local plant species
- relandscaping golf courses and cemeteries to contain biologically diverse vegetation
- leaving dead trees in woodlands to provide nesting cavities
- planning urban parks around riparian areas
- constructing migration corridors near or though urban areas
People can protect habitats far from where they live by the decisions they make at home. For example, consumers protect species when they refuse to buy furs, ivory products, shark’s fin products, or relics from endangered species. Consumers should also refuse to purchase exotic birds, reptiles, turtles, tropical fish, and animals caught in the jungle, and they should avoid buying rare cacti, orchids, and exotic plants and trees, or wood and paper products derived from old-growth forests.
Ecological restoration takes much longer than reconciliation because it depends almost entirely on natural processes to rebuild components of the habitat. Reconciliation is faster because it alters the environment to mimic a habitat rather than rebuild it. Sometimes successful restoration or reconciliation becomes impossible because the habitat is too badly ruined. In those cases environmental scientists turn to either ecosystem replacement or artificial ecosystems.
In ecosystem (or habitat) replacement, biologists replace a degraded ecosystem with another type of ecosystem that has a greater chance of sustaining native species. For example, a growing town may have destroyed a forest 50 years ago, but the same town can rehabilitate the area by creating a botanical park containing native vegetation. Artificial ecosystems consist of new constructed habitat rather than any attempt to restore the habitat in cooperation with nature. A rebuilt wetland or a rebuilt coral reef offers an example of an artificial ecosystem (or habitat). Though artificial ecosystems sometimes bear little resemblance to the original habitat, many have proved to be successful places for native species to live. Coral reef scientist Thomas Goreau has explained the role of underwater metal structures as a substitute for damaged coral reefs: “Under these conditions, traditional [revival] methods fail. Our method is the only one that speeds coral growth.” But the Nature Conservancy’s coral reef expert Rod Salm shared with the Associated Press in 2007 his opposing view on the limited value of artificial reefs: “The extent of [coral] bleaching . . . is just too big. The scale is enormous and the cost prohibitive.” Perhaps artificial habitat will serve as one of many ways to help species from going extinct, but science cannot depend on any single method to save endangered animals.
Human Populations and Biodiversity
Human population growth affects biodiversity in two main ways: massive numbers of people change the environment—global warming is the primary example—and urban areas expand into less developed areas. Expansion into rural land brings with it the hallmarks of city life: roads, congestion, pollution, noise, and wastes.
Humanity affects biodiversity in a general sense because of its impact on the earth and the atmosphere. Developed societies are also industrialized societies with a high level of consumerism, so they exert a larger ecological footprint on the planet than nonindustrialized societies. An ecological footprint is the amount of land and water needed to support one person and absorb that person’s wastes. The amount of cropland, grazing land, forests, and fishing grounds plus carbon-based fuel and nuclear fuel consumption factors into a single ecological footprint. For instance, a typical U.S. resident has a footprint of about 24 acres (0.1 km2); a typical resident of India has a footprint of less than 2 acres (0.01 km2). Subtle things also contribute to ecological footprint because not all industrialized nations have footprints equal to that of the United States. Germany’s is about 11; France’s and the United Kingdom’s are each less than 14.
Carbon footprint is a component of ecological footprint and equals the amount of carbon-based fossil fuels used and the waste made by burning those fuels. Environmental organizations such as the Nature Conservancy calculate carbon footprint as follows: the amount of forestland needed to remove from the atmosphere the end-products of burning a unit of fossil fuel. The Nature Conservancy’s online calculator determines the carbon footprint for any household by answering questions on energy use, vehicle type and daily travel, diet, and waste recycling. The calculator
then automatically determines an individual’s or household’s carbon footprint as tons of carbon dioxide equivalents produced per year. Equivalents means that all greenhouse gases have been converted to an equivalent amount of carbon dioxide based on the degree of global warming they cause. Ecologists have determined that carbon footprint makes up almost half of a typical ecological footprint, and it has grown faster than any other component, especially in countries with a high level of consumerism. For example, the world carbon footprint is 2.64 acres (0.01 km2) per person, ranging from nonindustrialized countries such as Peru and Somalia that produce a carbon footprint of 0 acres compared with that in the United States, 13.6 acres (0.05 km2) per person. The United States owns the third-highest carbon footprint, behind the United Arab Emirates (22 acres [0.09 km2]) and Kuwait (16 acres [0.06 km2]). Watching television, buying clothes, visiting a gym, and spending a day at the beach provide a short list of examples of carbon-emitting activities. Euan Murray, strategy manager of the Carbon Trust in Great Britain, told Britain’s Independent in 2006, “This piece of work [calculating carbon footprint] is about making people aware that everything they do involves carbon emissions and not just flights and heating their homes.” The term carbon footprint shows up increasingly in the media, but as Murray suggests, how does a large carbon footprint affect ecology?
The continued growth of ecological and carbon footprints puts animals and plants in peril because Earth’s biota can no longer support the current number of people. Since about 1988 the ecological footprint of Earth’s human population has exceeded the planet’s capacity to support it. This attribute is called biocapacity, and as humans continue to stress biocapacity, other species will lose hold on their natural habitats. This scenario may be altered, however, if people make major changes in their relationship to natural resources. The purpose of green technologies is to find ways to preserve biocapacity by conserving natural resources.
Almost every human activity affects biodiversity in a negative way. All types of industries, agriculture, recreation, and general consumption lead in some way to ecosystem degradation. Furthermore, the natural world seems to have become a foreign concept to many. Each year people are injured or killed because they did not understand animal behavior in nature. It is not unusual, for example, to see visitors at national parks leap from their cars and rush too close to bears, elk, moose, coyotes, and other wildlife. National Geographic writer John G. Mitchell once observed while visiting Tennessee’s Great Smokey Mountains National Park, “Enthralled visitors often assume—mistakenly—that roadside creatures are too tame to be dangerous.” Urbanization has simply disconnected people’s lives from nature. Many city residents go weeks, months, or even years without experiencing a day free from human influence.
The rapid increase in the world’s human population since the 1800s has been the root of today’s threats to the environment and to biodiversity.
holds heat. At the same time, deforestation leaves fewer trees to absorb carbon dioxide, the most abundant greenhouse gas. In 2007 the Intergovernmental Panel on Climate Change released a report, “Climate Change 2007: Synthesis Report,” that was the product of six years of work plus research on previous studies by hundreds of researchers from more than 100 nations. It stated, “Warming of the climate system is unequivocal, as is now evident from observations of increases of global average air and ocean temperatures, widespread melting of snow and ice and rising average global sea level.” Put another way, there should no longer be any question of whether climate change is real and caused by humans.
Much of the damage to the Earth’s biomes from global warming may be irreversible, but two technologies exist for rescuing the remains of habitats in peril: restoration ecology and reconciliation ecology. Restoration ecology comprises the activities for returning a damaged habitat disturbed to its original state. Reconciliation ecology comprises the actions that make a habitat suitable for sharing between humans and native species. The case study “The Everglades” discusses how these methods work.
Humanity affects biodiversity in a general sense because of its impact on the earth and the atmosphere. Developed societies are also industrialized societies with a high level of consumerism, so they exert a larger ecological footprint on the planet than nonindustrialized societies. An ecological footprint is the amount of land and water needed to support one person and absorb that person’s wastes. The amount of cropland, grazing land, forests, and fishing grounds plus carbon-based fuel and nuclear fuel consumption factors into a single ecological footprint. For instance, a typical U.S. resident has a footprint of about 24 acres (0.1 km2); a typical resident of India has a footprint of less than 2 acres (0.01 km2). Subtle things also contribute to ecological footprint because not all industrialized nations have footprints equal to that of the United States. Germany’s is about 11; France’s and the United Kingdom’s are each less than 14.
Carbon footprint is a component of ecological footprint and equals the amount of carbon-based fossil fuels used and the waste made by burning those fuels. Environmental organizations such as the Nature Conservancy calculate carbon footprint as follows: the amount of forestland needed to remove from the atmosphere the end-products of burning a unit of fossil fuel. The Nature Conservancy’s online calculator determines the carbon footprint for any household by answering questions on energy use, vehicle type and daily travel, diet, and waste recycling. The calculator
then automatically determines an individual’s or household’s carbon footprint as tons of carbon dioxide equivalents produced per year. Equivalents means that all greenhouse gases have been converted to an equivalent amount of carbon dioxide based on the degree of global warming they cause. Ecologists have determined that carbon footprint makes up almost half of a typical ecological footprint, and it has grown faster than any other component, especially in countries with a high level of consumerism. For example, the world carbon footprint is 2.64 acres (0.01 km2) per person, ranging from nonindustrialized countries such as Peru and Somalia that produce a carbon footprint of 0 acres compared with that in the United States, 13.6 acres (0.05 km2) per person. The United States owns the third-highest carbon footprint, behind the United Arab Emirates (22 acres [0.09 km2]) and Kuwait (16 acres [0.06 km2]). Watching television, buying clothes, visiting a gym, and spending a day at the beach provide a short list of examples of carbon-emitting activities. Euan Murray, strategy manager of the Carbon Trust in Great Britain, told Britain’s Independent in 2006, “This piece of work [calculating carbon footprint] is about making people aware that everything they do involves carbon emissions and not just flights and heating their homes.” The term carbon footprint shows up increasingly in the media, but as Murray suggests, how does a large carbon footprint affect ecology?
The continued growth of ecological and carbon footprints puts animals and plants in peril because Earth’s biota can no longer support the current number of people. Since about 1988 the ecological footprint of Earth’s human population has exceeded the planet’s capacity to support it. This attribute is called biocapacity, and as humans continue to stress biocapacity, other species will lose hold on their natural habitats. This scenario may be altered, however, if people make major changes in their relationship to natural resources. The purpose of green technologies is to find ways to preserve biocapacity by conserving natural resources.
Almost every human activity affects biodiversity in a negative way. All types of industries, agriculture, recreation, and general consumption lead in some way to ecosystem degradation. Furthermore, the natural world seems to have become a foreign concept to many. Each year people are injured or killed because they did not understand animal behavior in nature. It is not unusual, for example, to see visitors at national parks leap from their cars and rush too close to bears, elk, moose, coyotes, and other wildlife. National Geographic writer John G. Mitchell once observed while visiting Tennessee’s Great Smokey Mountains National Park, “Enthralled visitors often assume—mistakenly—that roadside creatures are too tame to be dangerous.” Urbanization has simply disconnected people’s lives from nature. Many city residents go weeks, months, or even years without experiencing a day free from human influence.
The natural world is everywhere disappearing before our eyes— cut to pieces, mowed down, plowed under, gobbled up, replaced by human artifacts.Climate change, or specifically global warming, symbolizes the dangers wrought on the environment by human activities. Earth has always possessed natural rhythms consisting of long periods of colder temperaxvitures and long periods of warmer temperatures. This has led some people to believe that global warming results from a natural cycling of temperature rather than a continuous and increasing phenomenon. Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado, told the New York Times in 2008, “Too many think global warming means monotonic relentless warming everywhere year after year. It does not happen that way.” Today’s combination of greenhouse gases in the atmosphere and deforestation has caused, nevertheless, a dramatic rise in the average of year-to-year global temperatures than at any other time in Earth’s history. Greenhouse gases—volatile organic compounds, ozone, methane, and carbon dioxide and other exhaust emissions—trap the Sun’s heat in the atmosphere like a glass greenhouse—Edward O. Wilson
The rapid increase in the world’s human population since the 1800s has been the root of today’s threats to the environment and to biodiversity.
holds heat. At the same time, deforestation leaves fewer trees to absorb carbon dioxide, the most abundant greenhouse gas. In 2007 the Intergovernmental Panel on Climate Change released a report, “Climate Change 2007: Synthesis Report,” that was the product of six years of work plus research on previous studies by hundreds of researchers from more than 100 nations. It stated, “Warming of the climate system is unequivocal, as is now evident from observations of increases of global average air and ocean temperatures, widespread melting of snow and ice and rising average global sea level.” Put another way, there should no longer be any question of whether climate change is real and caused by humans.
Much of the damage to the Earth’s biomes from global warming may be irreversible, but two technologies exist for rescuing the remains of habitats in peril: restoration ecology and reconciliation ecology. Restoration ecology comprises the activities for returning a damaged habitat disturbed to its original state. Reconciliation ecology comprises the actions that make a habitat suitable for sharing between humans and native species. The case study “The Everglades” discusses how these methods work.
Urban Development
In the last 200 years the percentage of the U.S. population living in cities increased from 5 percent to almost 80 percent. Th is increase in urban population has also caused more urban sprawl. Urban sprawl is defi ned as the growth of human populations in areas that previously had low population density. Such outward spread results when people feel the need for more space, safer neighborhoods, aff ordable housing, and, ironically, a place where they can live closer to nature. Of course, urban sprawl usually destroys natural habitat by reducing woodlands, grasslands, desert, or wetlands. Urban sprawl also fragments habitat and pollutes it, increases the incidence of wildlife killed on roads, and increases soil erosion, which begins a breakdown of many ecosystems.
Th e spread of human populations is unlike population growth and decline in the natural world. Animals and plants adjust their birthrate in conjunction with resource availability, but people do not do the same when they build cities higher and farther. If people continue consuming resources with little regard for the future, the environment may reach a point at which it cannot sustain the number of people on Earth. Al Gore wrote in An Inconvenient Truth, “. . . death rates and birth rates are going down everywhere in the world, and families, on average, are getting smaller. But even though these hoped-for developments have been taking place more rapidly than anyone would have anticipated a few decades ago, the momentum in world population has built up so powerfully that the ‘explosion’ is still taking place and continues to transform our relationship to the planet.” More than twice as many people live on Earth today than lived here in 1950, when the earliest environmental laws were passed.
Populations with fast growth rates contain the fastest-growing urban centers; China and India provide examples of rapid urbanization. These two countries account for more than one-third of the world’s total population growth and, though most of their populations live in rural areas, both have very large rural-to-urban migrations. China and India each will soon reach a milestone that the world achieved in 2007: for the first time ever, more people live in cities than in rural areas.
Developing countries in 2007 had twice the birthrate per 100,000 people (22.1) than developed countries (11.0), and their populations increase at about 1.4 percent a year. Developing countries also possess a disproportionate amount of the world’s plant and animal diversity. The economies of developing countries are also growing quickly, signaling increases in urban centers, housing, and roads, which all threaten habitat. Booming economies also cause secondary effects on the environment: expansion of agricultural monoculture, air and water pollution, and noise and light
pollution. Despite the economic growth in developing countries, a large number of people still live in poverty in these places—people who feel they must harvest their natural resources for income. This combination of increasing economic growth with widespread poverty has had a crippling effect on biodiversity.
Part of the Biodiversity Treaty addresses the needs of developing nations while at the same time addressing biodiversity loss. The treaty made provisions for compensating developing nations so that their citizens would not be forced to destroy native plants and animals for food or income. Though the treaty may be flawed in some people’s minds, it represented an important step by calling for cooperation from more than 150 nations to preserve biodiversity in all parts of the world, not just within national boundaries.
Th e spread of human populations is unlike population growth and decline in the natural world. Animals and plants adjust their birthrate in conjunction with resource availability, but people do not do the same when they build cities higher and farther. If people continue consuming resources with little regard for the future, the environment may reach a point at which it cannot sustain the number of people on Earth. Al Gore wrote in An Inconvenient Truth, “. . . death rates and birth rates are going down everywhere in the world, and families, on average, are getting smaller. But even though these hoped-for developments have been taking place more rapidly than anyone would have anticipated a few decades ago, the momentum in world population has built up so powerfully that the ‘explosion’ is still taking place and continues to transform our relationship to the planet.” More than twice as many people live on Earth today than lived here in 1950, when the earliest environmental laws were passed.
Populations with fast growth rates contain the fastest-growing urban centers; China and India provide examples of rapid urbanization. These two countries account for more than one-third of the world’s total population growth and, though most of their populations live in rural areas, both have very large rural-to-urban migrations. China and India each will soon reach a milestone that the world achieved in 2007: for the first time ever, more people live in cities than in rural areas.
Developing countries in 2007 had twice the birthrate per 100,000 people (22.1) than developed countries (11.0), and their populations increase at about 1.4 percent a year. Developing countries also possess a disproportionate amount of the world’s plant and animal diversity. The economies of developing countries are also growing quickly, signaling increases in urban centers, housing, and roads, which all threaten habitat. Booming economies also cause secondary effects on the environment: expansion of agricultural monoculture, air and water pollution, and noise and light
pollution. Despite the economic growth in developing countries, a large number of people still live in poverty in these places—people who feel they must harvest their natural resources for income. This combination of increasing economic growth with widespread poverty has had a crippling effect on biodiversity.
Part of the Biodiversity Treaty addresses the needs of developing nations while at the same time addressing biodiversity loss. The treaty made provisions for compensating developing nations so that their citizens would not be forced to destroy native plants and animals for food or income. Though the treaty may be flawed in some people’s minds, it represented an important step by calling for cooperation from more than 150 nations to preserve biodiversity in all parts of the world, not just within national boundaries.
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