Science

Climate change: the silent agony of the rainforest

They did not expect such a massacre. Yet researchers from the Smithsonian Center for Environmental Research, Oxford University and the National Research Institute for Sustainable Development (IRD) are categorical: tree mortality in several Australian rainforests has doubled in recent decades. Their work, based on observations of more than 8,300 trees at 24 sites over nearly half a century, has just been published in the journal Nature. And they can have serious consequences for our future.

Several studies have already alerted us to the alarming state of some of the rainforests that make up the green lungs of the planet. This should be more accurate thanks to simulations and Australian databases running for almost 50 years. “When we compare the 70s and 80s with the last three decades, we realize that the annual tree death rate has doubled, from 1% to 2%. This may seem low in absolute terms, but this phenomenon applies to large areas. a major trend that potentially leads to a halving of the lifespan of trees and therefore the time of carbon storage in trunks. This is a very important result that has very important implications when it comes to the role of forests in climate change mitigation. says forest biologist and ecologist David Bauman, one of the study’s lead authors.

“Climate change affects”

It would take more work to say that what is happening in Australia is likely to be happening elsewhere. However, the average climatic conditions of the Australian forests seem to be quite representative of most of the tropical rainforests found in other regions of the planet. In addition, the increase in mortality measured there closely follows the increase in temperature. This causes significant stress by causing the plants to sweat. “This mechanism undoubtedly plays a big role in increasing mortality. Of course, it is possible that other phenomena come into play. But the overall result seems clear: it’s climate change,” explains David Bauman.

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If this theory is confirmed, tropical rainforests could soon become carbon sources. “This will mean that future temperature projections may be underestimated by current models. The task of limiting warming to well below 2 degrees will become more urgent and difficult, which will give even more weight to the warning messages contained in the latest IPCC report,” the expert continues.

Should we then massively reforest? Pay attention to the ideas you get. “Planting trees takes a lot of time and requires a lot of money and energy with a high failure rate. In some regions, this should be part of the toolkit used to mitigate climate change. But given the urgency of the situation, it is better to focus our efforts on preserving existing forests and, of course, on reducing greenhouse gas emissions, says David Bauman.

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Especially since other indicators turn red. This Wednesday, May 18, the UN reported that four key indicators of climate change have broken new records in 2021: greenhouse gas concentrations, sea level rise, temperatures and ocean acidification. The report is “a deplorable enumeration of humanity’s inability to combat climate change,” condemned UN chief António Guterres.

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