Biodiversity

The term “biodiversity”—short for biological diversity—was first used in the 1980s by scientists to refer to the richness of biological variation on Earth or within a particular region. In their book Saving Nature’s Legacy, ecologists Reed Noss and Allen Cooperrider define biodiversity as

the variety of life and its processes. It includes the variety of living organisms, the genetic differences among them, the…ecosystems in which they occur, and the ecological and evolutionary processes that keep them functioning, yet ever changing and adapting.

As this definition suggests, biodiversity exists on several levels. Perhaps the most common definition of the term refers to the variety of different species on the planet or in a given habitat. Approximately 1.7 million species of plants, animals, fungi, microbes, and other forms of life have been identified and named by biologists, but estimates of the total number of species on this planet vary greatly, from ten million to one hundred million. Scientists are engaged in several efforts around the world to identify and number undiscovered species, and many environmental laws, such as the Endangered Species Act, focus on preventing their disappearance or extinction.

The concept of biodiversity also extends to different levels of biological organization. Genetic diversity refers to the genetic variation within the same species. This can cover distinct populations of the same species (rice, for instance, exists in thousands of distinct varieties) or genetic variation within the same population (cheetahs in Africa, for example, lack genetic diversity in that all members are very similar in their genetic makeup). Scientists also refer to ecosystem diversity, noting the presence on Earth of a wide variety of natural habitats that contain differing varieties of life and ways in which species interact with each other. The World Resources Institute states that “the breadth of the concept [of biodiversity] reflects the interrelatedness of genes, species, and ecosystems.”

Biodiversity at all levels is an important environmental resource. “Our lives depend on biodiversity in ways that are not often appreciated,” writes scientist Anthony C. Janetos. He and other observers have described several different ways in which humans rely on biodiversity. On a utilitarian level, humans depend on other species for food, clothing, wood, medicines, and other necessities and comforts of living. Domesticated strains of crop plants and animals are continually interbred with their wild “cousins” to introduce new genetic combinations that can improve yields, drought tolerance, and disease and pest resistance. Endangered species of plants or animals may have properties yet to be discovered that could provide important medicines. In addition to such direct benefits, the world’s diverse living creatures working in concert provide important ecological “services” such as air and water purification, climate regulation, erosion control, and providing oxygen in the atmosphere that humans need to breathe. “Biodiversity keeps the planet habitable,” concludes biologist Peter Raven. Some ecologists also stress the aesthetic value of a natural world rich with an abundance of varied and often beautiful life-forms.

These important benefits conferred by biodiversity may be at risk, some believe. “Biologists who explore biodiversity see it vanishing before their eyes,” writes Edward O. Wilson. Conservationists have classified eight thousand species as endangered, and the true number of species nearing extinction may be much higher. Scientists such as Denis Saunders of Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) estimate that seventy-thousand species become extinct each year—almost two hundred species a day. Many argue that the world could possibly lose 50 percent of its species over the next century. These extinctions are primarily blamed on the pressures exerted by a human population that has grown from less than 1.75 billion in 1900 to more than 6 billion in 2000. Human activities such as hunting, fishing, logging, the conversion of natural habitat into farmland and urban areas, and the spread of non-native species into fragile ecological areas are all blamed for species extinction and declining biodiversity. “In both direct and indirect ways,” writes ecologist R. Edward Grumbine, “human activities are causing a biodiversity crisis—the largest mass extinction in 65 million years.”

Despite widespread agreement within the scientific community on the importance of biodiversity, some areas of contention remain. One concerns the extent of the extinction crisis. Extinction, most biologists agree, is a natural phenomenon that has occurred throughout world history; the question is whether contemporary extinction rates are abnormally high. Some scientists have argued that dramatic estimates in the thousands of species becoming extinct every year are speculative guesses without supporting data and that the number of documentedextinctions remains relatively small. “The world is not losing species very rapidly yet,” argues science writer Dennis T. Avery. Moreover, Avery and others contend that most known extinctions have taken place on islands, which have small populations that are highly vulnerable to extinction and therefore do not necessarily demonstrate the existence of a biodiversity crisis elsewhere.

Disagreement also exists regarding the ramifications of species loss. People who may be concerned about the fate of the panda or blue whale may feel less sense of loss if an undiscovered species of beetle in the tropical rainforest becomes extinct—a far more likely scenario. In many cases, another species may simply replace the ecological niche or function of a species that became extinct. “Losing a species may be tragic,” writes author Mark L. Plummer, “but the result is rarely, if ever, catastrophic.” Conservationists retort that the cumulative ramifications of loss of biodiversity may very well damage the resiliency of ecosystems.

A third area of controversy revolves around proposed remedies for preventing loss of biodiversity. Since human activities are believed to be the main threat to biodiversity, most proposed solutions—such as setting aside land as wildlife habitat, banning hunting of animals, restricting logging—inevitably result in restrictions on human activities and create economic burdens. Many conservationists believe that these are costs that humanity must shoulder. But some observers argue that due to the scientific uncertainty as to the extent and ramifications of loss of biodiversity, broad conservation measures attempting to restrict human activities might not be warranted or should at least be weighed against other social goals. “Species are menaced to improve roads to hospitals, build university campuses, create affordable housing, make the raw material for newspapers and magazines, and create a host of other social goods,” argues Plummer. “When we alter or cancel these projects to benefit nature, we make life harder for human beings.”

Humanity faces some critical choices about whether and how to preserve global biodiversity. Many scientists believe the twenty-first century will be a crucial time in determining the fate of many of this planet’s species and that actions people take now will have a significant and lasting legacy. The various contributors to Biodiversity: Current Controversies discuss the causes, repercussions, and solutions to declining biodiversity. It is hoped that the articles that follow will shed light on one of the truly global issues of our time.