Why are trees mostly found along rivers in the Great Plains?

The Great Plains are characterized by a continental climate with low precipitation, high winds, and significant temperature fluctuations, which generally favor grasslands over forests. Because the region experiences limited moisture—with rainfall decreasing significantly from east to west—the vast majority of the landscape is dominated by prairie grasses.12

Trees in the Great Plains are primarily restricted to "gallery" or riparian forests found along river corridors. These areas provide the necessary moisture and groundwater access that trees require to survive in an otherwise arid environment. These riparian zones support hardy, drought-tolerant species such as cottonwood and box elder, which can thrive in the specific conditions provided by river systems despite the surrounding dry climate.21