AT: Biodiversity Impacts 1. Global biodiversity at its highest point ever

AT: Biodiversity Impacts

1. Global biodiversity at its highest point ever

However, the rate at which species have become extinct has fluctuated over the various periods, and the number of species has generally increased up to our time, as can be seen in Figure 130. Never before have there been so many species as there are now. The growth in the number of families and species can be accredited to a process of specialization which is both due to the fact that the Earth’s physical surroundings have become more diverse and a result of all other species becoming more specialized. Even so, there have been several major occurrences of extinction—the best known of these is probably the last break in the curve 65 million years ago when most of the dinosaurs became extinct, but the most serious one occurred 245 million years ago when around half of all marine animals and four-legged vertebrates and two-thirds of all insects were wiped out.

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Bjorn Lomborg, Professor Political Science, University of Aarhus (Denmark), 2004, The skeptical environmentalist: measuring the real state of the world, p. 251

In the natural environment species are constantly dying in competition with other species. It is estimated that more than 95 percent of all species that have ever existed are now extinct. A species typically survives 1-10 million years. Translated to the case of our described 1.6 million species, we must reckon with a natural extinction of around two species every decade. Table 6 shows that about 25 species have become extinct every decade since 1600. Thus, what we see is clearly not just natural extinction. Actually, mankind has long been a major cause of extinction. Around the time of the last ice age, about 33 major families of mammals and birds were eradicated—an extremely large number, considering only 13 families had become extinct within the 1.5 million years prior to that. It is presumed that Stone Age man hunted these 33 families to extinction. The Polynesians have colonized most of the 800 or so islands in the Pacific over the last 12,000 years. Because the birds on these islands had developed without much competition they were extremely easy to catch and were therefore frequently hunted to extinction. By studying bones from archaeological excavations it has been estimated that the Polynesians in total have eradicated around 2,000 species of birds, or more than 20 percent of all current bird species. Mankind, then, has long been a cause of an increase in the extinction rate.

Richard B. Primack, Professor of Biology @ Duke University, 2002, Essentials of Conservation Biology,

http://www-personal.umich.edu/~dallan/nre220/outline23.htm

Captive breeding and subsequent re-introduction of a threatened species is an important and in some cases very successful tool for species conservation. Critics point to the need to conserve/restore habitat, list examples of failures, decry the cost, and argue we should rescue species before they are on the brink of oblivion. Fair enough. But, captive breeding saved the bison. Wolves roam Yellowstone and the Upper Peninsula of Michigan, the Peregrine Falcon is off the endangered species list, golden-lion tamarins thrive in the Brazilian forests, whooping cranes perform their mating dances along river banks in the west, and many more species might similarly be rescued. Zoos, botanical gardens and aquaria have found new purpose and direction, providing a safety net when other protective measures have failed.

Roger A Sedjo, Sr. Fellow, Resources for the Future, 2000, Conserving Nature’s Biodiversity: insights from biology, ethics and economics, eds. Van Kooten, Bulte and Sinclair, p. 114

As a critical input into the existence of humans and of life on earth, biodiversity obviously has a very high value (at least to humans). But, as with other resource questions, including public goods, biodiversity is not an either/or question, but rather a question of “how much.” Thus, we may argue as to how much biodiversity is desirable or is required for human life (threshold) and how much is desirable (insurance) and at what price, just as societies argue over the appropriate amount and cost of national defense. As discussed by Simpson, the value of water is small even though it is essential to human life, while diamonds are inessential but valuable to humans. The reason has to do with relative abundance and scarcity, with market value pertaining to the marginal unit. This water-diamond paradox can be applied to biodiversity. Although biological diversity is essential, a single species has only limited value, since the global system will continue to function without that species. Similarly, the value of a piece of biodiversity (e.g., 10 ha of tropical forest) is small to negligible since its contribution to the functioning of the global biodiversity is negligible. The global ecosystem can function with “somewhat more” or “somewhat less” biodiversity, since there have been larger amounts in times past and some losses in recent times. Therefore, in the absence of evidence to indicate that small habitat losses threaten the functioning of the global life support system, the value of these marginal habitats is negligible. The “value question” is that of how valuable to the life support function are species at the margin. While this, in principle, is an empirical question, in practice it is probably unknowable. However, thus far, biodiversity losses appear to have had little or no effect on the functioning of the earth’s life support system, presumably due to the resiliency of the system, which perhaps is due to the redundancy found in the system. Through most of its existence, earth has had far less biological diversity. Thus, as in the water-diamond paradox, the value of the marginal unit of biodiversity appears to be very small.