Favored by a subtropical climate that extends the growing season annually to as many as 341 days and coaxed with irrigation, the land produces vegetables and citrus that is unmatched except in Florida and California. What nourishes - sugar cane, grain sorghum, corn and other vegetables - in some regions gives way to what clothes - cotton. Land that is not farmed or committed to urban life in part supports ranching enterprises.
The four southernmost counties of Texas- Cameron, Hidalgo, Starr, and Willacy-make up the Lower Rio Grande Valley. Like any coastal plain, the region is generally flat, but rich alluvial soils afforded by the Rio Grande make the land comparable to farming regions in Florida and California.
The subtropical climate fosters agriculture, but the trend toward urbanization, the most rapid in the state and one of the most rapid in the nation, is projected to change land use. The population of the McAllen-Edinburg-Mission metropolitan area, home to both rapid development and agriculture, grew 48.5% between 1990 and 2000, according to the U.S. Census Bureau.
Fruits and vegetables produced in the Lower Rio Grande Valley are part of a modern commercial supply chain and are shipped out of the region, and few markets exist for local produce. The Rio Grande supplies most of the region's water, and water shortages, caused by Mexico's preventing inflows from Mexican tributaries in recent years, have had a negative impact on agricultural irrigation. Despite these shortfalls, water supplies in U.S. possession have so far met municipal and industrial demands. More pressing, from a health standpoint, is water quality, which is jeopardized by sewage and chemical contamination that occurs as the river runs through rapidly urbanizing and industrializing regions. High fecal coliform levels represent a potential health hazard to recreational users of the river, and risks accrued from irrigation are under study.