Proponents of conservation believe that saving species from extinction is important for many reasons. Species have both aesthetic and recreational value, as the tremendous popularity of zoos, wildlife safaris, recreational hiking, and wildlife watching (bird watching, whale watching, etc.) indicate. Wildlife also has educational and scientific value. In addition, because all species depend on other species for resources, the impact of a single lost species is difficult to predict and could potentially be immense. Scientists have shown that habitats with greater biodiversity are more stable—that is, they are better able to adjust to and recover from disturbances. This is because different species may perform overlapping functions in a biologically diverse ecosystem. Habitats with less diversity are more vulnerable, because a disturbance affecting one species may cause the entire network of interactions to collapse. Furthermore, many species have great economic value to human beings. Plants provide the genetic diversity used to breed new strains of agricultural crops, and many have been used to develop pharmaceutical
FIGURE 1.4 The northern spotted owl, which inhabits old-growth forests in the Pacific Northwest, was the subject of a lengthy battle pitting environmentalists against logging interests. (U.S. Fish and Wildlife Service.)
products. Aside from the economic or utilitarian reasons for preserving species, however, many people think that humankind has a moral responsibility to maintain the Earth's biodiversity. When species are lost, the quality of all life is diminished.
The Gallup Organization conducts an annual poll on environmental issues. In 2004 Gallup pollsters asked participants to express their level of worry about various environmental problems. As shown in Figure 1.5, more than 60% of those asked expressed a "great deal" or "fair amount" of concern regarding the extinction of plant and animal species. This placed extinction sixth in the listing of environmental problems in terms of amount of worry. Extinction was considered less pressing a problem than water and air pollution, but more worrisome than damage to the Earth's ozone layer, global warming, or acid rain. Sixty-one percent of those surveyed were also concerned about the loss of tropical rain forests—home to many of the world's imperiled species.
FIGURE 1.5 Public opinion about environmental issues, 2004 Lydia Saad, "Worry about Environmental Problems," in "Global Warming on Public's Back Burner," The Gallup Poll, April 20, 2004, http://poll.gallup.com/content/default.aspx?ci=11398 (accessed March 10, 2006). Copyright © 2004 by The Gallup Organization. Reproduced by permission of the Gallup Organization.
Are Some Species More Important than Others?
In general, the public places high value on some endangered species and not others. For example, whales and seals are popular animals for which protection measures receive widespread support. On the other hand, there are several species listed under the Endangered Species Act that are considered pests or predators, because they pose a threat to human livelihoods or safety. Utah prairie dogs are burrowing animals that produce networks of underground tunnels. The resulting holes and dirt mounds can ruin cropland and trip and injure livestock. The protection of Utah prairie dogs and other imperiled rodents is a source of contention for people who believe that the Endangered Species Act puts animal interests above human interests. The same debate rages over such predators as wolves and mountain lions that may prey upon livestock, pets, and even people.
From a scientific standpoint some species are more valued because they are the last remnants of biological groups that once flourished. Examples of these include the coelacanth, one of the few species (along with lung-fish) that help to document the transition from aquatic to terrestrial life in vertebrates, and the tuatara, a highly endangered reptile found only in New Zealand. The
extinction of species that have no closely related species left on Earth represent particularly significant losses to the genetic diversity of the planet.
Biological Indicator Species
The rapid rate of species loss should also concern human beings because many are dying out due to pollution and environmental degradation, problems that affect human health and well-being as well. Species that are particularly useful in reporting on the health of ecosystems are called biological indicator species. Environmental scientists rely on sensitive indicator species just as coal miners once relied on canaries to check air safety in underground tunnels, where dangerous gases frequently became concentrated enough to be poisonous. Miners carried a canary into the mineshaft, knowing that the air was safe to breathe as long as the canary lived. If the bird started to sicken, however, miners evacuated the tunnel. In the same way, the sudden deaths of large numbers of bald eagles and peregrine falcons warned people about the dangers of DDT, a powerful pesticide in wide use at the time. The disappearance of fish from various rivers, lakes, and seas also alerted people to the presence of dangerous chemicals in waters.
During the final decades of the twentieth century, many scientists became concerned about the sudden disappearance of many amphibians, particularly frogs, all over the world. Most troubling was the fact that many species disappeared from protected parks and wildlife refuges, areas that appeared relatively pristine and undisturbed. Amphibians are believed to be particularly sensitive to environmental disturbances such as pollution because their skins readily absorb substances from the environment. Their decline is a suggestion that all may not be well.