These include the grizzly bear, bald eagle, and gray wolf, among others. It makes sense to protect a species before it had declined too far. When its populations have become small or isolated, it is harder and more expensive to help the species recover. In addition, many plants and animals play an important role in their ecosystems, such as that of a keystone species. It is important to conserve species in many parts of their range so ecosystems remain healthy.
Many people think so.
Human populations depend on plants and animals for much of their food, medicines, clothing, and shelter. Perhaps even more important, intact ecosystems perform many vital functions, like purifying the air, filtering harmful substances out of water, turning decayed matter into nutrients, preventing erosion and flooding, and moderating climate. It is not known how many species can be eliminated from an ecosystem without its functioning being impaired. It is likely that an ecosystem with more species is more stable than one that has lost some species. For example, research has shown that grassland plots with a greater number of plant species are better able to withstand drought than those with less species diversity.