The mesquite originates in the Tamaulipan mezquital ecoregion, in the deserts and xeric shrublands biome, located in the southern United States and northeastern Mexico. It has extremely long roots to seek water from very far under ground. The region covers an area of 141,500 km2 (54,600 sq mi), encompassing a portion of the Gulf Coastal Plain in southern Texas, northern Tamaulipas, northeastern Coahuila, and part of Nuevo León. As a legume, mesquite is one of the few sources of fixed nitrogen in the desert habitat.