A new map shows where people have the lowest impact—but are those the best places to protect?
A newly created map reveals the “wildest” places on Earth—places where humans have the lowest impact. The findings could be used to support the push to set aside half of Earth for nature, its authors say.
“If you want to know where in the world you can find a place that has not yet been transformed by agriculture, infrastructure, or settlements, [this map] is where to find it,” says Erle Ellis, a global ecologist at the University of Maryland Baltimore County who contributed to the analysis. “There is a very strong consensus on where these places are.”
The map, published today in the journal Global Change Biology, knits together four independently developed models for determining where humanity leaves its fingerprints, each using different indicators of activity.
All four models use human population, built-up areas, and cropland as inputs, but then they start to specialize. The Global Human Footprint index also uses roads, railway lines, navigable waterways, night-time lights, and pasturelands to identify the places where humankind is least noticeable.
The Anthropogenic Biomes project maps various kinds of populated ecosystems, like the “Residential Rangelands” of Africa, where pastoral people live in medium densities. The Global Human Modification and the Low Impact Areas maps are more recent attempts to identify where humans aren’t. Both include data on livestock density; the former also looks at mining and energy production and the latter includes data on protected areas and deforestation.
Researchers behind the various efforts decided to come together and see how well their maps overlapped; pretty well, it turns out.
All of the maps agreed that about half of Earth shows “low” human impact, and about half of that—a quarter of the ice-free surface of the planet—could be described as “very low” human impact. Mostly, the maps assigned the same places to those categories. That’s not surprising, their creators say, since most of the areas that fit this category are either very cold, such as the tundra and boreal forest that stretches across the far north of the Americas and Eurasia, or very hot, such as the world’s deserts.
Each map looked at evidence for contemporary human transformation, so areas that were changed by humans in the past but don’t have lots of lights, roads, or people now are ranked as low impact.
For example, archeological research and ecological surveys of tree species increasingly suggest that the Amazon rainforest was thickly populated and carefully managed by humans for centuries. Layers of charcoal from controlled fires and groves of trees that were clearly planted by people, like açaí palms and cacao, still attest to those days. But since the forest is currently without extensive croplands or major infrastructure, much of the Amazon is ranked as “low impact” in the map.
Support for saving half the planet
The researchers say that because 50 percent of Earth has only low levels of human impacts, bold calls to preserve half of the planet for nature are achievable. Lead author Jason Riggio, a spatial ecologist at the University of California, Davis, hopes the map can bolster the case for making the goal of protecting half the planet by 2050 official at the next meeting of the Convention on Biological Diversity, scheduled for 2021.
Riggio says the group is not recommending that low-impact areas be made into strictly protected parks. Even many of the “very low” impact areas have people in them. “It is not about excluding people or setting up national parks where people aren’t allowed to do any use,” Riggio says.
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Instead, he says, such areas could be managed for both wildlife and human use, like the coffee farms certified as “bird friendly” by the Audubon Society. These farms grow coffee beans under a canopy of forest trees that provide habitat for birds.
But which half to save?
It’s not obvious, however, that protection efforts should focus only on low-impact areas.
The new map also shows that low-impact areas aren’t evenly distributed across ecosystem types. Less than one percent of temperate grasslands, tropical coniferous forests, and tropical dry forests have very low human influence.
And while preserving largely untouched “wilderness” is an important goal for many, it isn’t always where the most plant and animal species are. Globally, the tropics have many more species than the ecosystems closest to the poles, but the tropics also have a lot of people, according to Maria Dornelas, an ecologist at the University of St. Andrews in Scotland.
But, Dornelas says, “if we just preserve tropical forests, we lose all the polar bears and all the tundra plants and all the desert species.”
Dornelas and her colleagues recently made their own global map—this one looking at threats to plant and animal species, from climate change to deforestation to pollution. Their map looks quite different, with hotspots of threats in India, Northern Europe, and the East China Sea. It highlights the fact that without protection or restoration, species and ecosystems in areas with high human impact may be more likely to disappear.
In the end, no map can tell humanity what we should protect. Should we focus on low-impact areas to preserve “wild” places, or on high-impact areas where threats to species are most urgent?
“Ultimately, this is a map of human societies, not a map of nature,” Ellis says. “How you interpret this map in relation to nature depends on what your values are.”