By Margot Higgins Polar bears are among the most affected by global warming.
Studies show diminished body size in many bears.
Imagine a deciduous forest in the Arctic. Global warming could dramatically alter a third of the world's natural habitat over the next 100 years, according to a study released Wednesday by the World Wide Fund for Nature . Previous efforts to model the potential effects of greenhouse warming on global ecosystems focused on flows of energy and matter through ecosystems rather than on species that make up ecosystems. The problem, the report finds, is that many plant and animal species will not be able to keep up with the modification of their habitat. According to the report, the rate of warming is expected to be much faster than the rate of warming that occurred during the most recent ice age 13,000 years ago.