ON A WARM JULY AFTERNOON I am going to see the mouth of the Rio Grande for the first time. Sixteenth-century Spaniards called the stream Río de las Palmas; the bright forest of palm trees around the mouth was a landmark for navigators of the Gulf. In good years, the lowlands surrounding those groves would be marshes teeming with shellfish and minnows hunted by ibis and herons stepping sprightly in the brine. But today, as I ride eastward on Texas Highway 4, the most striking features ahead are airborne white swirls of sand and salt. Decades of clearing for agriculture and development have isolated the last native sabal palms to a small Audubon preserve outside Brownsville, and most of the wetlands have gone as dry as chalk. The sprawling river delta has been reduced to a nearly barren, eroded strip of earth, and some residents of Port Isabel are having trouble breathing because there’s so much windblown grit in the air.
My guide is a pleasant man named Gilberto Rodriguez who grew up on a