The delicate balance of the Pantanal wetlands in southwestern Brazil may be forever altered by a massive project to straighten and dredge the area’s rivers. Powerful commercial interests in Brazil, Paraguay, Bolivia, and Argentina want to proceed with the Hidrovia project to improve barge navigation through the Paraguay River and other waterways in the region. But environmentalists say that the project would drain the Pantanal’s unique network of grasslands, swamps, rivers, and lakes at too fast a rate, turning large areas into deserts and destroying important habitat for fish and birds. Although the Brazilian government has pledged not to endanger the Pantanal, enviros worry it will cave under political pressure.