U.S. Climate Affected by Vegetation

Changes in Vegetation across the United States

These images show the (a) dominant vegetation type and (b) fractional areal coverage (%) of each grid cell by the dominant vegetation for the 1700, 1910, and 1990 vegetation cases.

The maps labeled 1700 are estimates of potential vegetation for the country under current climate conditions (i.e., without land use). Maps labeled 1910 and 1990 are estimates of land cover for those periods that include the effects of land-use history up to and including those years respectively.

These figures illustrate some of the large changes to the land cover patterns that are estimated to have occurred across the United States as the result of land-use activities. It can be seen that between 1700 and 1910, much of the U.S. was converted from forests to croplands. By 1910, forest cover over the United States was at or near its lowest point in 300 years. Since 1910, agriculture has substantially intensified in the central and western U.S., but decreased in the east. By 1990, croplands covered about 24 percent of the total land area, with farms occupying more than 90 percent of some regions in Iowa and eastern Nebraska. Forest cover has steadily increased, to near 40 percent of the total land area in 1990. CREDIT: Somnath Baidya Roy, Princeton University

Impact of Changing Vegetation Pattern on July Temperatures

These images show the difference in the simulated near-surface air temperature (K) averaged for the entire month of July between the three cases.

The change in land cover between the 1710 and 1910 cases produces significant warming in the east and southeast and significant cooling in the northern Great Plains region. During this period, these regions experienced large-scale growth of croplands at the expense of the natural vegetation (mostly forests in the east and grasslands in the Midwest and Great Plains).

Between 1910 and 1990, there is significant cooling in parts of the Great Plains where agriculture continued to expand. Slight warming is also observed in the southwest, where woodlands have replaced a few deserts.

The white line demarcates where temperature changes are significant. CREDIT: Somnath Baidya Roy, Princeton University

Changes in Vegetation across the United States

These images show the (a) dominant vegetation type and (b) fractional areal coverage (%) of each grid cell by the dominant vegetation for the 1700, 1910, and 1990 vegetation cases.

The maps labeled 1700 are estimates of potential vegetation for the country under current climate conditions (i.e., without land use). Maps labeled 1910 and 1990 are estimates of land cover for those periods that include the effects of land-use history up to and including those years respectively.

These figures illustrate some of the large changes to the land cover patterns that are estimated to have occurred across the United States as the result of land-use activities. It can be seen that between 1700 and 1910, much of the U.S. was converted from forests to croplands. By 1910, forest cover over the United States was at or near its lowest point in 300 years. Since 1910, agriculture has substantially intensified in the central and western U.S., but decreased in the east. By 1990, croplands covered about 24 percent of the total land area, with farms occupying more than 90 percent of some regions in Iowa and eastern Nebraska. Forest cover has steadily increased, to near 40 percent of the total land area in 1990. CREDIT: Somnath Baidya Roy, Princeton University

Impact of Changing Vegetation Pattern on July Temperatures

These images show the difference in the simulated near-surface air temperature (K) averaged for the entire month of July between the three cases.

The change in land cover between the 1710 and 1910 cases produces significant warming in the east and southeast and significant cooling in the northern Great Plains region. During this period, these regions experienced large-scale growth of croplands at the expense of the natural vegetation (mostly forests in the east and grasslands in the Midwest and Great Plains).

Between 1910 and 1990, there is significant cooling in parts of the Great Plains where agriculture continued to expand. Slight warming is also observed in the southwest, where woodlands have replaced a few deserts.

The white line demarcates where temperature changes are significant. CREDIT: Somnath Baidya Roy, Princeton University

Impact of Changing Vegetation Pattern on July Precipitation

These images show the difference in the simulated total precipitation (mm) for the entire month of July between the three cases.

Clearly, the impact of the land cover changes on precipitation is much smaller than that of precipitation.

The difference plot between the 1700 and the 1910 cases exhibits a significant reduction (more than 20 mm) of precipitation in the Central Lowlands and increase (more than 30 mm) over western Texas. A similar increase in western Texas can also be found when the 1910 and 1990 cases are compared, but otherwise the differences are small.

The white line demarcates where precipitation changes are significant. CREDIT: Somnath Baidya Roy, Princeton University

Constellations

The Solar System