Homo sapiens are dominating an increasing share of the mainland United States. Cities, towns, roads and other human land uses already shape about one-third of the landmass in the Lower 48 states, concludes a new analysis. By 2030, we could add a new “human footprint” the size of Indiana.

That forecast comes from a new approach to using digital maps to calculate the size of the human footprint developed by David Theobald, a geographer at Colorado State University in Ft. Collins. In the current issue of Landscape Ecology, Theobold uses a few basic factors – including vegetation, housing density, the existence of roads and highway traffic volume – to identify “human dominated” landscapes. In 1992, he found that humans had shaped up to one-third of the U.S. (or 2.6 million square kilometers). By 2001, that area had grown by another 80,800 square kilometers — and by 2030 he predicts natural areas could lose another 92,000 square kilometers (roughly the size of Indiana).

Wetlands are the ecosystem most likely to feel the boot, Theobold found. In 2001, 61% of wetlands were in or near landscapes modified by humans, compared to 15% of forested lands, 10% of grasslands, and 2% of shrublands. — David Malakoff

Source: Theobald, D. (2010). Estimating natural landscape changes from 1992 to 2030 in the conterminous US. Landscape Ecology, DOI: 10.1007/s10980-010-9484-z

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