In an alarming revelation that could potentially reshape our understanding of climate change, research has demonstrated that tropical forests lose their ability to function as carbon sinks when confronted with unusually hot and dry conditions triggered by El Niño. For years, these tropical forests have been instrumental in mitigating climate change by absorbing more carbon than they release, a phenomenon that has significantly curbed the devastating impact of escalating global temperatures.
However, a recent study has shown that during the 2015-2016 El Niño event, which resulted in the hottest temperatures ever recorded and widespread drought, South American forests were unable to act as carbon sinks. El Niño, a climate event characterized by a sharp increase in Pacific Ocean sea-surface temperatures, leads to significant shifts in the global climate system. The 2015-2016 event brought exceptionally hot weather to South America, and alarmingly, a similar event is currently underway.
Tropical Forests Lose Carbon Absorption Capacity During El Niño Events
Tropical forests, which have acted as crucial ‘carbon sinks’ for decades, lose their ability to absorb carbon in extraordinarily hot and dry conditions caused by El Niño, a recent study has revealed. These forests have been instrumental in reducing carbon in the atmosphere, thus moderating the impacts of climate change.
El Niño and its Impact on Forests
El Niño, a climate event characterized by a significant increase in sea-surface temperatures in the Pacific Ocean, triggers a massive shift in global climate patterns. During the 2015-2016 El Niño, South American forests experienced unprecedented drought and the highest recorded temperatures, rendering them incapable of functioning as carbon sinks.
Dr. Amy Bennett, study leader and research fellow at the University of Leeds, stated, "Investigating what happened in the Amazon during this huge El Niño event gave us a window into the future by showing how unprecedented hot and dry weather impacts forests."
Findings of the Study
The research, published in the journal Nature Climate Change, was conducted by over 100 scientists across 123 experimental plots spanning Amazon and Atlantic forests, as well as drier forests in tropical South America. These plots have mostly acted as carbon sinks for the past 30 years, with tree growth exceeding mortality. However, during the 2015-2016 El Niño event, tree mortality increased due to intense heat and drought, causing the carbon sink to shut down.
Professor Beatriz Marimon of Mato Grosso State University in Brazil noted, "While tree growth rates resisted the higher temperatures, tree mortality jumped when this climate extreme hit." Out of the 123 plots studied, 119 experienced an average monthly temperature increase of 0.5C, with 99 plots also suffering water deficits.
Implications for the Future
Interestingly, forests accustomed to drier climates were found to be more vulnerable to drought, contrary to the expectation that wetter forests would be most affected. This suggests that some trees are already operating at the limits of tolerable conditions, according to the research team.
However, Professor Oliver Phillips, an ecologist at the University of Leeds who supervised the research, expressed optimism about the resilience of South American tropical nature. He noted that land clearance exacerbates dry and hot conditions, putting additional stress on remaining trees. "The big challenge is to keep forests standing in the first place. If we can do that, then our on-the-ground evidence shows they can continue to help lock up carbon and slow climate change," he said.
The findings underline the crucial role tropical forests play in mitigating climate change and the significant impact climate events like El Niño can have on these ecosystems. It is clear that protecting these forests is not just a matter of preserving biodiversity, but also a critical strategy in the fight against climate change. As we continue to grapple with increasing global temperatures, the need to safeguard these carbon sinks becomes even more pressing.