Richard Conniff: Wildlife in an Urbanized World


we know almost nothing about what ecologist Meredith Holgerson at Portland State University calls “these cryptic changes happening” as humans occupy and alter a landscape. For her doctoral research at Yale University, she looked at the effects of suburbanization on wood frogs in 18 ponds in the prosperous Connecticut suburb of Madison. The area around the ponds had developed largely with two-acre zoning, allowing for survival of “pretty good red maple swamps and vernal ponds,” says David Skelly, a professor of ecology at the Yale School of Forestry & Environmental Studies who oversaw the research. But chemical analysis of the ponds demonstrated that, along with other changes, the wood frog larvae were getting as much as 70 percent of their nutrients from materials leaching out of septic systems. “It suggests,” says Holgerson, “that tadpoles and other pond organisms are made up of human waste.”

The consequences of that remain unknown. But it also suggests that we may change the entire nutrient flow of an ecosystem, cause eutrophication, or introduce hormone-disrupting drugs or other chemicals in our waste — and still imagine that we live in a relatively intact habitat.