Climate Change and Biodiversity

Climate change affects the Earth’s vegetation by altering normal cooling and warming cycles. On a short-term basis, warming of the atmosphere due to increased carbon dioxide and other greenhouse gases enhances ecosystems. Higher than normal carbon dioxide levels increase the photosynthetic activity, and this makes plants more efficient in using water, perhaps forestalling drought. Over long periods, however, global climate change hurts biodiversity by the mechanisms suggested by the United Nations Environment Programme’s World Conservation Monitoring Center and summarized in the following table.

Climate change alters ecosystems by changing vegetation growth and weather patterns. First, climate change alters the growing season for plants and trees and so affects the species whose breeding cycles depend on these plants and trees. For example, a tree that blossoms at a different time on the calendar affects the insects that carry pollen, and the altered insect
populations influence the feeding opportunities for birds and reptiles. Second, new weather patterns that increase the violence and frequency of storms or the severity of heat waves and drought also affect the health of species and their resistance to disease and pests.

Al Gore wrote in his landmark 2006 book, An Inconvenient Truth, “. . . we are facing what biologists are beginning to describe as a mass extinction crisis, with a rate of extinction now 1,000 times higher than the normal background rate. Many of the factors contributing to this
wave of extinction are also contributing to the climate crisis. The two are connected. For example, the destruction of the Amazon rain forest drives many species to extinction and simultaneously adds more carbon dioxide to the atmosphere.” Many animals already struggle to keep pace with climate change. Polar bears go hungry waiting for the Arctic ice to form
from which the bears hunt for seal; fish and crustaceans cannot breed in water too warm to supply their food; and the broods of migrating birds starve because the seedlings and insects they usually eat have come and gone because of changing weather patterns.


Small increases in the atmosphere’s average temperature have begun to alter habitats. Animal populations migrate to higher cool-temperature altitudes; fruiting trees and plants blossom ahead of schedule to meet the feeding needs of migrating birds; and northern, cold-climate forests become threatened in warmer temperatures. This diagram illustrates some of the changes that have been associated with increased average temperature.