to ecosystems. Streams in Montana designated for recreational trout fishing serve the needs of biota and the wishes of people; they conserve nature.
Preservation programs began in this country before naturalists learned of biodiversity. The Wilderness Act of 1964, for example, designates land areas in the United States for preserving the animals living there. Of all types of nature reserves, wilderness areas impose the strictest limitations on human activities and so allow animals to behave naturally and follow their normal breeding patterns.
In 1935 naturalists Aldo Leopold, Benton MacKaye, and Robert Marshall formed an environmental organization called the Wilderness Society and began the first organized effort to set aside vast tracts of pristine land solely as wildlife habitat. Each of these naturalists believed that land must belong to the public rather than be exploited solely for profit, but Marshall put his philosophy to work when he became director of forestry for the U.S. Department of the Interior (1933–37). He once said, “I should hate to spend the greater part of my lifetime in a stuffy office or in a crowded city.” From his director’s office, Marshall set aside 5 million acres (20,235
km2) of wilderness, land he as a teen had described as “the woods and solitude.” Today the BLM oversees about 400 million acres (1.6 million km2) of wilderness that permits of little or no human activities. Some human activities do creep in, however, making wilderness preservation one of the biggest challenges faced by protectors of the environment.
Proponents of wilderness development have long argued that the vast amounts of untouched land can sustain logging, mining, oil drilling, and off-road vehicles without affecting wildlife. Since the early 2000s, for example, government officials have targeted Alaska’s wilderness for oil drilling. Public policy expert Paul Driessen wrote in a 2005 article supporting new oil exploration in the Arctic National Wildlife Refuge (ANWR): “During eight months of winter, when drilling would take place, virtually no wildlife are present.” In addition Driessen argued that drilling in ANWR would actually threaten fewer animals than wind power, which kills thousands of birds each year.
Parts of this country’s wilderness now contain activities that Robert Marshall would probably find disheartening. The BLM, for instance, leases land for oil and gas drilling in several million acres of wilderness and the FWS grants right-of-way access for select individuals to enter wilderness areas for business purposes. Industries have used right-of-way permits to build telecommunication lines, pipelines, roads, trails, flumes, and canals. Wilderness also contains casual use, which means industry or scientists may enter undisturbed areas to map new right-of-way routes or collect study data.
Despite the strides of U.S. conservation groups, only about 4.6 percent of land in the United States is protected as part of the National Wilderness Preservation System under the authority of the Wilderness Act. (The IUCN ranks the United States 42nd among all nations in the amount
of land protected as wilderness.) Privately run organizations such as the Nature Conservancy, founded in 1951, dedicate labor and money to protect plants, animals, and ecosystems. Indeed private groups may provide a more hopeful future for habitat preservation than government programs because private groups steer clear of business interests better than government
leaders. The following table lists the main types of habitat protections in the United States.
The United Kingdom uses a designation called Environmentally Sensitive Areas, which protects agricultural lands that have value because of their wildlife, landscape, or history. These areas may support agricultural activities, but only in a way that protects the land and the biota. Regardless of the type of protection, the following principles should be followed in land conservation:
- large reserves are better than small reserves
- one large reserve is better than several small ones adding up to the same area
- reserves should be close together rather than far apart
- reserve lands should be clumped together rather than strung out in a narrow arrangement
- wildlife corridors should connect reserves
- round reserves work better than other shapes to minimize threats from the edges
- minimally developed buffer zones should surround reserves near populated places
Conservation biology comprises a field of study that helps in designating lands to be protected. Conservation biologists study species and habitat loss, habitat restoration, and biodiversity. Many of their studies rely on aerial mapping with the aid of global positioning systems (GPS)
and data-gathering satellites. Satellites map changes within a region over time, and these trends can then be analyzed to determine habitat losses or gains, called change data. Change data have been useful in showing
the effects of logging, roads, and rights-of-way on plant life and animal populations. The World Resources Institute, based in Washington, D.C., operates the Global Forest Watch program, which uses satellite images and geographic information systems (GIS) to assess two components of conservation land: intactness and size threshold. Intactness is the size of a single piece of undisturbed area that sustains natural ecosystems, and size threshold relates to the minimum land area required to support a species’ population and allow for its recovery.
Field studies also play a part in conservation biology. Rather than collecting data from high above the Earth, field studies include observations, animal counts, and animal tracking to learn the status of any species’ population. Trackers most often use radiotelemetry, a technique in which
a single animal in a herd or pack or other social group is caught, tranquilized, and fitted with a collar that emits an electronic signal. After the animal returns to its group, biologists track the group’s movements with an antenna that receives the signal. In this way research may be conducted far away from the animals and not disturb the group’s behavior.
Conservation biology studies draw on genetics, ecology, naturalresource management, and social sciences. Genetic tools help determine the presence of genes that may give a population of animals a better chance for survival. Ecology lends information on Earth’s various regions of vegetation and terrain, called bioregions, and how biota and the land work together. Natural-resource management balances the needs of people with the survival of forests, wildlife, and aquatic species. Finally, social sciences, such as anthropology, sociology, philosophy, and economics, play a role in conservation planning that accounts for the needs of humans.
Carrying capacity represents a critical part of all conservation studies. Carrying capacity means the maximum population that a species’ habitat can support over a period of time. As population density of any species increases, the capacity of its habitat to support it decreases.
↑ Population density → ↓ Carrying capacity
High population density forces more individuals to share a smaller piece of habitat. Food and shelter (nests, dens, burros, etc.) availability decreases, so mortality rates increase, usually for the following reasons: animals conflict with each other more often; increased pathogen and disease transmission; less protection from predators; inadequate shelter for offspring; and stressful interactions, leading to possible rejection from
One of the greatest threats to existing natural resources, including plant and animal species, comes from populations that exceed the land’s capacity to support them. The human population has grown exponentially from 1800 to today so that it has overshot its resources in many parts of the world. Natural populations of plants and animals adjust to overshoot by producing less offspring, but humanity has not, so today humans use more resources than the planet has the continued capacity to provide.
a protective social group. Species can adjust to dense populations for a time by taking in less food and by producing smaller litters, but these are short-term fixes that weaken the overall population.
When land and food is limitless, animal numbers increase in a logarithmic manner, meaning the numbers increase exponentially. Growth rate then slows as the population reaches the land’s carrying capacity. Many terrestrial mammals on Earth may have now reached their habitat’s carrying capacity, and they survive because of higher mortality rates and adjusted litter size.
When they can no longer make further adjustments, population size plummets, causing what is called a population crash. Species living as opportunists or competitors have a great impact on their population’s survival.
Opportunists are species designed to produce large numbers of offspring that receive little or no parental care and so can overcome population crashes. These species reproduce often and the offspring disperse quickly. Rats are an example of an opportunist species because they have
these traits. Competitor species reproduce late in life, produce few offspring, have long life spans, and one or both parents actively care for their young. Newborn of competitor species tend to be big and are born strong relative to opportunists; their size helps them survive to maturity. Wild
horses are an example of a competitor species.
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