Deforestation contributes more to global warming than previously thought

Deforestation in the Democratic Republic of Congo. The land will be used for agricultural purposes. Image credit: John Cannon

The fact that carbon released by deforestation on a large scale contributes to rising global temperatures is certainly not a new one. But now, a new research study, titled Are the impacts of land use on warming underestimated in climate policy? and released in August by the Environmental Research Letters, has indicated that the impact of clearing forests for agriculture and farming to produce food for a burgeoning world population is bigger than first thought.

“Normally people only think about what’s happening right now when they think about the carbon budget,” Natalie Mahowald, lead author of the research study and a climatologist at Cornell University, New York, United States (U.S.), said in a released statement. “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.”

While only about a fifth – or 20 per cent – of the carbon dioxide in the atmosphere can be traced to clearing forests, the “land use and land cover change” is behind a mind-whopping 40 per cent of global warming. But that is not down to only carbon alone that the cleared lands continue to emit into the atmosphere; the study also proves the lingering effects of the following release of nitrous oxide and methane into the air from lands that have been deforested.

One of the aims of the Paris Agreement was to keep global temperatures from rising more than two degrees Celsius by the end of the century. Currently, much of the effort has been directed to reducing the use of fossil fuels – which are carbon-based – for other, more sustainable, alternatives. But while Mahowald and her colleagues acknowledge and assent that approach, they also believe that the “primary target,” according to Mongabay, should be to curb the emissions from these energy sources.

“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,” Mahowald said. “Removing those particles actually makes it harder to reach the lower temperatures laid out in the Paris Agreement.”

However, this particular complication leads back to the need to examine and recognise the considerably underestimated consequences linked to deforestation.

Mahowald and her colleagues proved earlier this year that when forests, which also sequester carbon, are cleared for land use, the impact on the climate is multiplied. In the research study, the researchers modelled the rise of global temperatures based on the current rate of deforestation as found in the tropical region and then compared their findings with temperatures that would rise due to other sources of carbon emissions, such as the burning of fossil fuels for energy.

And the results are rather foreboding despite efforts to meet climate targets set. As the current rate of deforestation stands, global temperatures will likely rise 1.5 degrees Celsius more than what they originally were before the Industrial Revolution by the end of the century at 2100. However, the research scientists also found that even is all sources of emissions were found and cut even two years ago in 2015, the temperature increase would probably still happen.

In this case, there may be a higher chance of extreme weather, such as Hurricane Irma and Maria, a decrease in crop harvests, and more droughts. But according to a various research scientists in the Nature Climate Change journal, these weather events may become even more extreme in if temperatures do rise up to two degrees Celsius as seen in pre-industrial levels.

In conclusion, Mahowald and her team believe that policies and policymakers who are addressing the issue of climate change should look at deforestation as a major source of carbon emission, especially as demand for land for agricultural use grows in the tropics. Mahowald also thinks that the policies should also be geared for the long-term, and taking the “multi-centennial legacy of current land-use decisions” into account as well.

“When we think about climate change, we can’t stop at the end of the century,” Mahowald explained. “The consequences keep going for a couple more centuries.”


Sources: Nature Climate Change Journal, Environmental Research Letters, Mongabay, John Cannon