Humans Used to Be Good for the Planet, And We Can Be Again

As we grapple with climate change, an extinction crisis, and the legacy of extractive land use, many now assume that humans and the Earth are an inherently bad mix. But this wasn't always the case, according to new research.

A team of archaeologists, ecologists, anthropologists and conservation managers found that humans have been altering the planet for at least 12,000 years, and that much of that impact was good before industrialization and colonization took hold. Their work was published in the Proceedings of the National Academy of Science on Monday.

“There are very few places—only about 17 percent of Earth's land—that has never had people living in it,” said lead author Erle Ellis, professor of environmental science at the University of Maryland. “In most places, biodiversity was sustained for thousands of years by the people living there. In most cases, humans shaped that biodiversity in a positive way.”

Modern conservation was founded on the idea that there are two types of land: untouched, pristine nature and ruined, human-impacted environments. While many conservationists have now moved away from this idea, it remains a lingering paradigm. To trouble that hypothesis, researchers from across the world created maps that reconstructed historical human populations and land-use, then matched the data with current patterns of biodiversity. This involved projecting current maps of human population density and land-use into the past using the History Database of the Global Environment dataset (HYDE), then tracking changes over time. 

Their research showed that, by 10,000 BCE, humans were using nearly three-quarters of the planet. They also found that areas with high biodiversity today are correlated with areas with long histories of Indigenous stewardship. To measure biodiversity, the researchers used three indicators: vertebrate species richness, presence of threatened vertebrate species, and a metric called Key Biodiversity Areas that denotes areas of high biodiversity.

This research builds on the knowledge that cultural practices of many Indigenous and traditional societies—including setting fires, hunting, agriculture, and plant and animal domestication—created diverse landscapes that were home to many species. The current biodiversity crisis is not a problem of untouched land becoming touched, the findings indicate. Rather, it is a product of colonization, and the resultant intensification of land-use. 

Believing that the best way to protect land is to leave it alone has created major problems for modern society. One classic example, said Ellis, is the centuries of fire suppression since Europeans colonized the United States. Not only has this paved the way for megafires, he said, but it also affects species that have evolved to rely on fires. 

Of course, the clock can’t be reversed. There are now too many people on the planet to be supported by traditional land management practices alone, and some level of intense land use is necessary. However, Ellis said that just because land use is intense, doesn’t mean it needs to be totally destructive. 

Currently, many landscapes are homogenized, with whole swaths of land dedicated to crops. One way to improve land management would be to diversify those regions, leaving some areas open to grasslands or forests. This won’t be easy, and will require more precautions against nearby herbivores and carnivores, but will ultimately improve the health of the land and the planet. 

For Ellis, the biggest takeaway of this research is the story of human relationships with the environment. The researchers argue that recognizing cultural connections to the land and empowering Indigenous environmental stewardship is a key strategy for protecting biodiversity. This is already starting to happen in some places. For example, Canada has organized both Indigenous and non-Indigenous working groups to hit biodiversity targets. 

"Global land use history confirms that empowering the environmental stewardship of Indigenous peoples and local communities will be critical to conserving biodiversity across the planet," the authors wrote in the study.