Conservation And Restoration Biology

As human populations have increased rapidly, so has the human impact on ecosystems. Scientific understanding of these impacts is weak, but is improving. Meanwhile, individuals, such as the students in Figure 22-9, can contribute to scientific understanding and also take responsibility for minimizing human impacts on ecosystems.

In a discipline called conservation biology, scientists seek to identify, protect, and manage natural areas that still retain much biodiversity. Where humans have had the largest impacts— agricultural areas, former strip mines, and drained wetlands, for example—biologists must often devise plans to reverse changes and replace missing ecosystem components. In restoration biology, scientists deal with extreme cases of ecosystem damage. For example, restoring a grassland community to an area that was strip-mined may involve recontouring the land surface, reintroduc-ing bacteria to the soil, planting grass and shrub seedlings, and using periodic controlled fires to manage the growth of vegetation.

Dwarf wedge mussels are an endangered species in the Aschuelot River of New Hampshire. These high school students from a nearby town are making a census of mussel populations to help save the species from extinction and to monitor water quality in the river.

Even the best scientific efforts may not be able to completely restore an ecological community. But biologists can encourage restoration by applying their understanding of processes such as energy flow, species interactions, and biogeochemical cycling.

Species and Habitats

One principle that biologists have learned to apply is that species and their habitats are interconnected. Figure 22-9 shows students studying dwarf wedge mussels (Alasmidonta heterodon) in the Ashuelot River in New Hampshire. In 1990, government biologists classified this mollusk as an endangered species because its population was declining rapidly. The students looked for clues to explain the decline. The dwarf wedge mussel is a bioindicator, a species that is especially sensitive to ecological change. Because the mollusk is harmed by tiny amounts of water pollution, it acts as an early warning signal for environmental problems. Its decline suggested a pollution problem in the Ashuelot River, and the students' research helped to find the source of the pollution.

Case Study: Saving the Whooping Crane

The whooping crane, or "whooper," is an example of a species that is on the road to recovery, thanks to protective laws, international cooperation, and the efforts of volunteers. Before 1870, about 20,000 whoopers migrated annually between Canada and the Gulf Coast. Then, American settlers began to hunt the birds for their feathers and drain the marshes where birds fed during migrations.

By 1937, only about 15 whoopers remained. Meanwhile, the federal government had begun to regulate the hunting of migratory birds and then established a winter refuge for the cranes in Texas. In 1967, the U.S. Fish and Wildlife Service established a captive breeding program for the cranes, and people learned how to encourage whooper reproduction. For example, Figure 22-10 shows a man imitating a courtship dance with a female crane. This ritual dance prompts female cranes to produce eggs, which can then be fertilized artificially with a male crane's sperm. The resulting offspring may survive in the wild, but may not know how to migrate.

figure 22-10

(a) To help save whooping cranes from extinction, conservationists have tried to recreate many aspects of the crane's natural lives, including the courtship dance shown here. (b) Several generations of cranes have been bred and raised in captivity and released into the wild, although with mixed success.

figure 22-10

(a) To help save whooping cranes from extinction, conservationists have tried to recreate many aspects of the crane's natural lives, including the courtship dance shown here. (b) Several generations of cranes have been bred and raised in captivity and released into the wild, although with mixed success.

At one point, biologists tried placing whooping crane eggs in the nests of wild sandhill cranes in the hopes that the sandhill cranes would raise the whooper chicks and teach them to migrate. The whooper chicks did learn to migrate but did not learn how to court other whoopers for successful mating.

Captive breeding programs now produce about 30 whooping crane chicks each year. To be sure that the chicks learn to live with other whoopers, the people who raise the chicks wear crane costumes or use crane puppets. The young cranes are released into the wild, but they will not migrate on their own. Since 2001, pilots have used small aircraft to lead cranes along their historical 2000-mile migration route. Like many migratory birds, the cranes learn the route after one trip.

The whooping crane case shows that protecting species from extinction is not easy. But it can be done with creative ideas, cooperation, an understanding of each organism's biology, and the efforts of ordinary citizens.

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