A national wildlife refuge near Elk Grove, Calif., is part of a far-reaching effort to assess water and soil conditions in some of the nation's most vulnerable ecosystems.

Stone Lakes National Wildlife Refuge is among the more than 1,000 areas being studied that could help shape protection efforts of wetlands and aquatic resources.

Up to 95 percent of the nation's wetlands have been wiped out or modified, said Jonathan Bishop, chief deputy director of the State Water Resources Control Board, one of the partners of the survey. Nutrient-rich and easy-to-till wetlands were historically seen as good farmland, but many of the areas have been damaged or transformed by development.

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