About 160 U.S. ski resorts, including the nation’s 20 largest, have pledged to work on greening the ski industry by conserving energy and water and restricting sprawl. The resorts yesterday unveiled a first-of-its-kind “Sustainable Slopes” charter that lays out dozens of rules governing resort management and construction of new facilities. The charter calls for high-density development to help curb sprawl, reductions in water used for artificial snowmaking, regular environmental audits, and a number of other steps designed to reduce environmental impact. Still, most enviros dismissed the charter as “greenwashing.” They are calling for an end to ski-resort expansion, which destroys forests and wildlife habitat, and for greater restrictions on snowmaking, which depletes streams.