By taking up farming and raising livestock on ever larger scales, people in the ancient world also started dealing a blow to the natural environment not only by clearing forest but by altering the very climate of the planet.
We’ve been changing the climate ever since we started farming
Several celebrated scientists and historians like Jared Diamond and Yuval Hariri see the Agricultural Revolution as an unmitigated disaster in the history of our species.
By giving up a freewheeling hunter-gatherer lifestyle in favor of tilling the soil with the sweat of their brows most people around the world unwittingly condemned themselves to miserable lives. They lost their freedom to roam around, they ended up living in squalid communities where diseases were rampant, and they came to be at the mercy of the rich and powerful in newly stratified societies.
By taking up farming and raising livestock on ever larger scales, people in the ancient world also started dealing a blow to the natural environment not only by clearing forest but by altering the very climate of the planet. So say scientists who have published a study in the journal Scientific Reports. Ancient farming practices, the researchers say, increased emissions of the heat-trapping gases carbon dioxide and methane, which drive climate change. And that rise has, of course, been ongoing ever since.
“Had it not been for early agriculture, Earth’s climate would be significantly cooler today,” says lead author Stephen Vavrus, who is a senior scientist in the University of Wisconsin-Madison Center for Climatic Research in the Nelson Institute for Environmental Studies. “The ancient roots of farming produced enough carbon dioxide and methane to influence the environment,” he adds.
In other words, we have been unknowingly changing the planet’s climate for millennia. Then again, perhaps that should not come as a surprise, seeing as we have observably been altering landscapes far and wide, usually for the worse, and from there it’s only a small step for the effects of our actions to influence the entire planet itself.
For most of its 4.5-billion-year history, Earth’s climate has largely been determined by a natural phenomenon known as Milankovitch cycles, which are periodic and astronomically predicable changes in the shape of Earth’s orbit around the sun as well as the way the planet wobbles and tilts on its axis. The cycles influence how and where sunlight is distributed on the planet’s surface, thereby changing both local and global weather patterns.
Yet by pumping vast amounts of heat-trapping gases into the atmosphere, we have been influencing the effects of one such cycle. The planet should be cooling right now, yet it’s been demonstrably warming.
According to Ruddiman’s so-called Early Anthropogenic Hypothesis, widespread deforestation in Europe beginning some 6,000 years ago, the emergence of large farming settlements in China 7,000 years ago, and the spread of rice paddies (which are large sources of methane) in Asia some 5,000 years ago already began to have a marked impact on global weather patterns.
“I noticed that methane concentrations started decreasing about 10,000 years ago and then reversed direction 5,000 years ago and I also noted that carbon dioxide also started decreasing around 10,000 years ago and then reversed direction about 7,000 years ago,” Ruddiman says.
Early agriculture “put greenhouse gases into the atmosphere and that was the start of it all,” the scientist adds. “The phenomenal fact is, we have maybe stopped the major cycle of Earth’s climate and we are stuck in a warmer and warmer and warmer interglacial.”
