National Geographic : 1995 Oct
knowledge and tireless assistance. He worries that use of the valley's surface water and the pumping of aquifers for irrigation may be causing the water table to fall, though scientists have not confirmed this. When I talked with W. L . Minckley of Arizona State University, acknowledged dean of Cuatro Ci6negas biology, he agreed that the valley's aquatic habitats are threatened, not just by local water users but also by increasing recreational use. Mexico's Desert Aquarium "Both national and interna tional efforts are needed to preserve this spectacular wetland for posterity," he warns. The Cuatro Cienegas region has been inhabited for some 10,000 years; the first canals were probably dug by Spanish settlers in the 1600s. Most of the valley's water is too laden with minerals for human consumption, and farmers using it for irrigation usually have to mix it with fresh water.