The greatest continuing threat to playas is culturally-accelerated sediment accumulation from row-crop agriculture. These sediments may interfere with the shrinking and swelling of the clay layer, which is vital to aquifer recharge, and reduce playa volume and length of time a playa will hold water, which significantly affects the plant and wildlife community supported by the playa. Modifications such as pits, ditches, berms, and roads also pose a threat to playas. These modifications concentrate water in a smaller area, thus reducing suitable habitat for water-dependent birds.