Historical vegetation patterns

Researchers used written descriptions by early explorers, historical photographs and land surveys to reconstruct what the Walker Basin looked like prior to agricultural development. They then compared these results to what we see today, using aerial photos and on-the-ground mapping, to determine if some plant communities were more affected than others by the development of the basin.

Agriculture was introduced to the Walker Basin in the 1850s. Irrigated agriculture, grazing and invasive species have all contributed to changes in the landscape during the past 150 years. Walker Basin was once used to graze cattle and harvest wild hay. Gradually, areas were converted to higher quality hay, such as alfalfa.

As irrigation techniques improved, larger areas were used for farming and some of the most productive natural areas (wet meadows, sagebrush and grasslands) were cleared and leveled.  The channelization of the river, ground water pumping and intensive grazing dried out the surrounding lands. This shifted the plant communities towards plants that were more adapted to drier conditions; approximately 44 percent of the meadow and wetland areas were changed to shrubland as a result of these drier conditions. Another 41 percent of the wetlands and meadows were directly converted to support agricultural production.

Cottonwood trees became more prevalent in the Walker Basin as the valley was settled, especially near homesteads. However, cottonwoods have largely stopped regenerating in the Walker Basin since the mid-20th century due to flood control; floods are necessary for cottonwood seedling establishment. Despite increases in cottonwoods in most areas, they have declined along the lower reaches of the Walker River, likely a result of the dropping water table that occurred partly due to river incision as the result of the dropping lake level. Plant communities have changed noticeably since the beginning of the 20th century, with large amounts of land shifting from wet to dry conditions.