Is the human species doing enough to conserve the rest of the world’s species for posterity? If not, then how much is enough? This is a key question, and opinions about the correct answer vary widely. An industry spokesperson is likely to ask, “Don’t they (the conservationists) have enough already?” “How much do they want, anyway?” This is a typical but inappropriate response, first, because the issue is really a scientific one, and second, because it puts conservationists in the awkward position of having to say that reserving a certain amount of habitat will be sufficient to save nature.
The only correct answer from a scientific standpoint is, “all of it.” That is how much of Earth was available to nature before modern man entered the picture. Since then, at least half of Earth’s terrestrial environment has been degraded or completely transformed to support the human enterprise. We know that half or more of Earth’s native habitat cannot be eliminated without endangering large numbers of species. In fact, more than 100 species have gone extinct in the U.S. alone since the Endangered Species Act (ESA) was approved by Congress. An additional 1200+ species are currently listed as endangered, and an even larger number of unlisted candidate species lurks in the background. This should be warning enough that humans are pushing our luck in preempting Earth’s resources for ourselves. Thus, the best answer to the question, “How much do they want?” is “Everything that is left.” Admittedly, this is a tall order, but it should be the goal that conservationists set for themselves.
If everything that is left is the goal (roughly 50% globally), how far are we from reaching it? Clearly, a very long way, but at this point definitions become important. If one means the strictest category of protected areas (equivalent to U.S. national parks), the global value is around 6% (for the U.S. it is 1.5%). From this perspective, the effort to conserve nature has barely begun. Nevertheless, in parts of the world there remain great expanses of unprotected land that continue to support natural vegetation and wildlife (much of the Amazon Basin, for example, and much of Siberia). Little of this land holds much promise for agriculture, so there should be no compelling reason to destroy it. The fate of these lands will depend more on politics than on social or economic necessity.