Nathaniel Scharping writes: Ever since our ancestors cut rough paths through the wilderness, humanity has been laying down trails. From footpaths to highways, a global network of roads binds communities and facilitates the exchange of goods and ideas. But there is a flip side to this creeping tangle of pathways: The roads that bring us closer also serve divide ecosystems into smaller parcels, turning vast expanses into a jigsaw of human mobility.

In a study published in Science, an international team of researchers attempted to quantify the extent to which roads have sliced up the globe. They used data from OpenStreetMap, a crowd-sourced mapping project, to chart how much land is covered by roads. For the purposes of their project, they defined a roadway as everything within a kilometer of the physical road itself (studies have shown measurable impacts on the environment extending out at least that far).

They estimated that roughly 20 percent of land is occupied by roads, not including Greenland and Antarctica. Although that leaves 80 percent as open space, this land is far from whole. Transected by highways and streets, the road-free areas are cut up into some 600,000 individual parcels. Half of these are less than a square mile, while only 7 percent span more than 60 square miles. The true impact of roads seems to be the gradual tessellation of once-cohesive landscapes. [Continue reading…]