Deforestation has double the effect on global warming than previously thought

In the fight against climate change, much of the focus rests on reducing our dependence on fossil fuels and developing alternative energy sources. However, the results of a new study suggest that far more attention should be paid to deforestation and how the land is used subsequently – the effects of which make a bigger contribution to climate change than previously thought.

The research, conducted by Cornell University and published in the journal Environmental Research Letters,shows just how much this impact has been underestimated. Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature.

Most scientists believe that a temperature increase of 1.5 degrees above pre-industrial levels will bring dangerous disruption to the world's climate. Indeed, many already think this target may be unattainable.

"A lot of the emphasis of climate policy is on converting to sustainable energy from fossil fuels", said Natalie M. Mahowald, the paper's lead author. "It's an incredibly important step to take, but, ironically, particulates released from the burning of fossil fuels – which are severely detrimental to human health – have a cooling effect on the climate. Removing those particulates actually makes it harder to reach the lower temperatures laid out in the Paris agreement."

Mahowald argues that in addition to reducing reliance on fossil fuels, scientists and policymakers must pay more attention to deforestation and the subsequent changes in land use for agricultural and other human industry. The negative consequences of this process are manifold.

When deforestation occurs, the burning of trees and plants releases carbon dioxide – a greenhouse gas – into the atmosphere. The problem is compounded when the land is then converted to farming or other human usage, releasing large amounts of other greenhouse gases like methane and nitrous oxide. Furthermore, the deforested area can no longer function as a carbon sink – trees and plants absorb carbon dioxide from the atmosphere.

The research showed this process has double the overall warming contribution than previously thought making it "twice as important" in Mahowald's eyes.

"Normally people only think about what's happening right now when they think about the carbon budget," Mahowald said. "But if you think about what's going to happen over the lifetime of that land, long into the future, you should multiply that land conversion by two to understand the net effect of it."

As agriculture expands in the tropics and pressure to turn rainforest into cropland increases, Mahowald advocates looking further forward in time to truly assess the impact that these practices have on the climate.