In the arid region south of Mexicali, where the pale desert dominates the landscape, the Las Arenitas wetland feels like a mirage. But it is real, and is an oasis for endemic and migratory birds that cross the Colorado River delta. Photograph: Pablo RomeroIn the sewage plant, solids and sediments are first removed from the wastewater. Before the overexploitation of the Colorado River, its delta crossed Baja California and Sonora until it met the waters of the Gulf of California, resulting in more than 400,000 hectares of wetlands. Seeking to mimic that strength, the Las Arenitas artificial wetland is a pause to the devastation of the local landscape.