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Was the Planet Ever Really Pristine?

Not for thousands of years, researchers say—and it’s time we owned up to that fact.

By Nathan Collins


A deforested portion of the Amazonian rainforest. (Photo: Antonio Scorza/AFP/Getty Images)

Look around any modern city, town, or rural hamlet and you’ll see the affect humans have had on our world. City lights and airplane noise now touch even the wildest places left on Earth. Meanwhile, deforestation, climate change, and pollution threaten our world’s essential biodiversity. Yet the idea that this is a modern phenomenon is wrong, a newreport argues: We’ve been messing with our planet for thousands of years.

“Recognizing the long-term human shaping of global biodiversity is … key to understanding contemporary human-ecology interactions and to predictive modeling of future transitions,” Nicole Boivin and her colleagues write today in Proceedings of the National Academy of Sciences. “Determining the consequences of past ecological change will also inform predictions of how modern communities may respond to ongoing anthropogenic or climatic factors,” and how long-lasting the resultant changes may be.

How have humans shaped their environment, and how has that affected biodiversity? For one thing, humans pretty much took over the world some 12,000 years ago, having colonized every continent, in many cases deliberately re-shaping their environments along the way. According to a 2010 study, for example, humans in the New Guinea highlands used stone tools to clear forests and make way for nuts and yams nearly 50,000 years ago. Similarly, there are hints that the first humans to arrive in California’s Channel Islands, around 12,000 to 14,000 years ago, dramatically changed the patterns of wildfire there, which had important consequences for the islands’ ecology.

We’ve been messing with our planet for thousands of years.

Then, of course, there’s the rise of agriculture, which began sometime around 12,000 years ago. By around that time, humans were deliberately clearing land to plant species of their own choosing (and sometimes ones that they had created themselves through hybridization). Land use for livestock and rice had a measurable impact on methane emissions in Asia between 4,000 and 8,000 years ago, according to a 2011 study in the Holocene. And, the authors point out, domestication helped make a few species—pigs and dogs among them—ubiquitous around the world, long before urbanization and the establishment of modern trade networks. Chickens, for example, were domesticated in East Asia thousands of years ago. They now outnumber humans three to one.

Whether humans’ impacts on our environments are bad or good—not all of our impacts are necessarily bad, the authors argue—scientists need a stronger grasp on the past in order to better understand our future. “Highlighting a long-term human role in shaping biodiversity does not absolve present-day populations of taking responsibility for Earth’s environments,” Boivin and her colleagues write. “Instead, it reaffirms the human capacity for ecological transformation … and suggests that we should own up to our role in transforming ecosystems and embrace responsible policies befitting a species that has engaged in millennia of ecological modification.”