Last week, it was revealed that a swath of the Amazon rainforest is now emitting far more CO2 gas than it is able to absorb, affecting its function as a carbon sink for the world. Now, researchers in the UK and Brazil have studied the effects of the 2015 drought that resulted in the destruction of billions of trees and vines, and turned a portion of the ancient rainforest into one of the world’s largest polluters.
Researchers discovered that an unprecedented amount of trees and plants died following the 2015 El Niño drought due to wildfires sparked by dry conditions, causing a large increase in carbon dioxide emissions, according to the study, which was published on Monday by PNAS. The study measured CO2 emissions for three years following El Niño, showing that the impact of a severe drought lasts for years.
The Lower Tapajós, the epicenter of the drought, only makes up 1.2 percent of the Amazon rainforest but emitted 495 million tons of carbon dioxide during the study period. The study notes that this level of carbon emissions exceeds the amount released from countries such as the UK and Australia. The carbon emissions in this region alone were also higher than a whole year's deforestation within the entire Amazon rainforest.
Only around a third (37 percent) of the emissions were re-absorbed by plant growth in the forest after three years, showing that the Amazon's vital function as a carbon sink can be hampered for years following a drought.
Erika Berenguer, lead author of the study, told Motherboard that Brazil could have been better prepared for the drought since the country was already well aware of how severe that year’s drought would be. “It's impossible to send firefighters to an area the size of Europe,” she said. “But what can be done is that we know what areas are going to be most impacted by the drought, so we can direct firefighters to those areas, for example, and extra financial resources.”
The 2015 El Niño was the hottest and driest of all previously recorded El Niños since 1998, according to the study. Over 2.5 billion trees were killed in its epicenter due to the extreme drought and wildfires.
Although the study only analyzed three years of data found by researchers, Berenguer shared that the team collected another year of data that couldn't be analyzed in time for publication, and that the COVID-19 pandemic halted any further investigation in the area.
Wildfires are not a natural part of the Amazon rainforest ecosystem due to its humid climate, but human activities such as deforestation fires or selective logging make it far more susceptible to them. Researchers found that trees in these human-modified areas, which Berenguer estimates could be more than 1 million square kilometers, were more likely to die from fires.
“If trees become more vulnerable to die when a fire occurs, and if they are in this forest, this might mean that we have 1 million square kilometers of more vulnerable forests,” Berenguer said.
Conservation efforts have been severely impacted since the 2019 election of Brazil president Jair Bolsonaro, who has emboldened the agricultural industry to ramp up deforestation in the Amazon, usually done using fire.
“Internationally, we need action to tackle climate change, which is making extreme droughts and fires more likely. At the local level, forests will suffer fewer negative consequences from fires if they are protected from degradation,” principal investigator Jos Barlow said in a press release.
The frequency of El Niño and similar weather events occurring will only increase as global temperatures and carbon emissions increase.
“We are decreasing the resilience of the Amazons towards climate change,” Berenguer said.