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While enjoying those long, lazy Sunday drives, you probably don't think about global warming as you ease past rolling hills and farmlands, but a new study offers further proof that changes to our countryside and land cover play a role in shaping our climate.

Above: Land cover map of the Unites States. Click image for larger picture. Map Key Credit: NASA

Recognizing the greatest human impacts on nature have taken place since the Industrial Revolution, research scientist Somnath Baidya Roy of Princeton University and others set out to discover how changes in land cover and vegetation in modern times have affected the summer climate of the United States.

Vegetation: The Neglected Player in Climate Change

While many studies have compared past and present climates with current and potential vegetation, this research used data and computer models from NASA and other organizations to trace vegetation pattern changes over the United States since 1700 at the local, regional, and continental level.

The study found that land cover changes produced a significant cooling effect in parts of the Plains and Midwest, as agriculture generally expanded and replaced grasslands. Farmlands tend to create lower temperatures because of increased evaporation.

Above: Changes in Vegetation across the United States Click image for larger picture. Credit: Somnath Baidya Roy, Princeton University

On the other hand, the Atlantic coast experienced a slight warming effect, where croplands replaced forests. Compared to forests, croplands are less efficient in transpiration - a daytime process where water evaporates from leaves during photosynthesis and cools the air. Temperatures have also warmed across the Southwest, where woodlands replaced some deserts.

Baidya Roy also found that changes in land cover had a domino effect, as changing temperatures led to the creation of new precipitation patterns. For example, the cooler conditions over the central U.S. weakened the temperature difference between land and the Gulf of Mexico, slowing the northward progression of weather systems and resulting in more rain across Texas but lower amounts across the Central Lowlands.

The Consequences of a Changing Landscape

Since changes in land cover are not uniform and fairly inconsistent, scientists are still grappling with its overall impact on climate change. In the U.S., for instance, changes in landscape have been quite variable and complex during the past 100 years, making it more difficult for scientists to reach concrete conclusions. But, this study and others have shown it is important to attempt to understand the effects of changing land cover, because they might mitigate or exacerbate greenhouse warming.

"In the U.S., over the past 100 years, it seems to be offsetting greenhouse warming. The opposite is probably true in most other parts of the world,"said Baidya Roy.

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For more information on this and other related research, please visit:

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Goddard Space Flight Center