Climate Change : Overview and Implications for Wildlife

The Earth’s climate is vastly different now from what it was 100 million years ago when dinosaurs roamed the planet and tropical plants thrived closer to the poles. It is different from what it was only 20,000 years ago when ice sheets covered much of the Northern Hemisphere. Although the Earth’s climate will surely continue to change, climatic changes in the distant past were driven by natural causes, such as variations in the Earth’s orbit or the carbon dioxide (CO2) content of the atmosphere. Future climatic changes, however, will probably have another source as well—human activities. Humans cannot directly rival the power of natural forces driving the climate—for example, the immense energy input to the Earth from the sun that powers the climate. We can, however, indirectly alter the natural flows of energy enough to create significant climatic changes. The best-known way people could inadvertently modify climate is by enhancing the natural capacity of the atmosphere to trap radiant heat near the Earth’s surface—the so-called greenhouse effect. This natural phenomenon allows solar energy that reaches the Earth’s surface to warm the climate. Gases in the atmosphere such