Many scientists believe that global climate change has already affected organisms on Earth—and will continue to do so in the near and far future. For example, a warmer world would cause the expansion of certain groups that spread in warmer climates, such as certain insects, algae, and nematodes; such changes could potentially change the landscape of infectious diseases. New species—from either mutations or those that thrive best in a warmer climate—could essentially introduce, or even reintroduce, harmful parasites into the world—ones that could affect not only humans, but other organisms, such as the beneficial insects that pollinate plants. New diseases—either from other organisms or more resistant bacteria and viruses—could also wreck havoc on organisms worldwide.

The main reason for scientific study of global climate change is obvious: The impact on climate changes on organisms—in the oceans, on land, and in between—can (and will) be enormous. This includes changes in organism diversity and habitats; changes in vegetation (for example, areas once good for growing experiencing extended droughts); and other environmental factors that will create competition between organisms for food or shelter, or even becoming extinct. In addition, because the population is over seven billion (to date) and over 50 percent of humans live near the oceans, the rise in ocean waters will be nothing less than deleterious. So far, the biggest question eludes most scientists: How long will it take before we reach some of these changes—or are we already at those thresholds of climate change?