World has lost a 10th of all its wilderness in the past two decades

Wilderness areas on Earth have experienced alarming losses in the past two decades, a new study suggests. By comparing global maps from the present day and the early 1990s, researchers have concluded that a 10th of all the world's wilderness has been lost in just 20 years.

The study, published Thursday in the journal Current Biology, finds that just over 30 million square kilometers (or 11.5 million square miles) of wilderness remains on Earth, composing nearly a quarter of the planet's terrestrial area. On the other hand, 3.3 million square kilometers have been lost since the early 1990s.

The losses were more pronounced in some areas than in others. South America lost nearly 30 percent of its wilderness area, and Africa lost about 14 percent. Overall, most of the remaining wilderness is concentrated in North America, North Asia, North Africa and Australia, the researchers note.

"Wilderness was defined as any area on Earth which didn't have a human footprint," explained James Watson , an associate professor at the University of Queensland, director of science and research at the Wildlife Conservation Society and the new study's lead author. "Wilderness" has no minimum size threshold — but scientists do often consider areas greater than 10,000 square kilometers to be "globally significant." As the researchers point out, this is the size threshold for sites containing intact ecological communities, according to the International Union for the Conservation of Nature.

And it's the loss of these globally significant wilderness areas that has the authors of the new study most concerned. Out of the 3.3 million square kilometers of wilderness lost, 2.7 million of them came from globally significant wilderness blocks.

In the early 1990s, there were 350 blocks of wilderness large enough to fit the globally significant criteria. The study suggests that 37 of them have fallen below the threshold since then, and 74 percent of all of them experienced some sort of loss. In fact, some types of ecosystems on Earth — these include tropical and subtropical coniferous forests, tropical and subtropical dry broadleaf forests and mangrove forests — now have no globally significant wilderness area left at all, the study finds.

The researchers also point out that while we've lost 3.3 million square kilometers of wilderness since the 1990s, we've only set aside 2.5 million square kilometers for protection in the same time period.

The researchers suggest that current conservation efforts tend to target areas that are already heavily degraded in an effort to save them, with less attention paid to intact areas that still may be in danger of losses down the line.

"There's been a huge focus on these degraded landscapes, species that are facing extinction — and that's a really good thing to do, we should always do that," Watson said. "But we've neglected the quality areas that are slowly dwindling away."

And this is a problem for more than just the species living in these areas. Big, contiguous swaths of wilderness — especially forests — often serve as key carbon sinks. This makes them important buffers in the fight against climate change. When these areas are degraded, on the other hand, they lose their carbon, and it adds to the greenhouse gas emissions humans are already pouring into the atmosphere.

The authors suggest several approaches aimed at better protecting wilderness areas in the future. International conventions and agreements should recognize and prioritize the ecosystem services provided by intact wilderness areas. International funding programs — for example, the Green Climate Fund — should allocate greater resources to the protection of these areas. And individual countries should be encouraged to develop more stringent national policies aimed at preserving their own natural landscapes.

Failing to take the problem seriously could lead to "largely irreversible outcomes for both humans and nature," the researchers cautioned in the paper. "[I]f these trends continue, there could be no globally significant wilderness areas left in less than a century."