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.
