A new study suggests the world's forests are more fragmented than ever before. Analysis by researchers at North Carolina State University showed that if one were to be dropped randomly into one of the world's many forests, there would be a 70 percent chance of being within a half-mile of the forest edge.

And if forests are fragmented, so are vital habitats. Researchers point out that development -- whether urban, suburban or agricultural -- continues to carve up forests, fields and wetlands, and the ecosystems they contain. A single road may not seem like much of an impediment to humans, but a two-lane stretch of pavement can sever a vulnerable piece of habitat.

To quantify habitat fragmentation, researchers at N.C. State used satellite imagery to build a map of global forest cover. Computer analysis showed that very few forests remain unaffected by human development.

"It's no secret that the world's forests are shrinking, so this study asked about the effects of this habitat loss and fragmentation on the remaining forests," study author co-author Nick Haddad, a biologist at N.C. State, explained in a press release.

"The results were astounding. Nearly 20 percent of the world's remaining forest is the distance of a football field -- or about 100 meters -- away from a forest edge," Haddad said. "Seventy percent of forest lands are within a half-mile of a forest edge. That means almost no forest can really be considered wilderness."

The only truly intact forests that remain are in the Amazon and the Congo.

Haddad and his colleagues say their new numbers have serious implications, given previously amassed evidence that shows fragmentation is directly correlated with shrinking biodiversity. Earlier studies have shown ecological fracturing to reduce the diversity of plants and animal species by anywhere from 13 to 75 percent.

"Some results showed a 50 percent or higher decline in plant and animals species over an average of just 20 years, for example," Haddad added. "And the trajectory is still spiraling downward."

While there are some mitigation options -- preserving larger chunks of habitat and installing wildlife corridors that connect multiple fragments of wilderness -- Haddad says that humans must act fast before species are lost forever.

The study, funded by the National Science Foundation, was published this week in the journal Science Advances.