There are edible flowering plants dependent on rainfall that take pressure off the grasses. They have become a good management tool. In the early 1930s the Soil Conservation Service in cooperation with New Mexico State University conducted re-seeding trials. Laman's love grass from South Africa was the only grass that met with success. It's now crowding out better grasses.
Pasture grasses compete with ever-increasing numbers of creosotebush and mesquite bushes.
Creosotebush is not palatable for livestock. Mesquite pods are palatable but the seed is not digestible. It passes through animals and is distributed through their manure, choking out native grasses on the rangeland. Goats are being used in Texas to keep the mesquite population under control. That research has not been successful in New Mexico.