‘May fight climate change’ from the Amazon rainforest

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For decades, IT has been the topic of concern among environmentalists, as vast parts of the rainforest have vanished to make room for human activity.

But, after all, the Amazon rainforest might not be on the edge of the brink – as certain areas are more resilient than previously believed to climate change, new research reveals.

Quite wet areas may potentially benefit from slightly warmer temperatures in the Amazon, the world’s largest tropical rainforest, scientists claim.

Forests consume between 20 and 30 percent of the carbon dioxide (CO2) we produce by photosynthesis, which is used to create food through chemical process plants.

But rising global temperatures due to climate change are weakening the mechanism, a process known as water stress, by reducing the amount of water in the soil and drying out the air.

Whilst previous research has cautioned that if photosynthesis stalls in waterlogged areas, climate change may intensify, this may not be true for all parts of the forest.

Actually, dry air could encourage plants to shape more productive leaves in very humid regions, increasing photosynthesis, the researchers said.

“Study author Dr. Pierre Gentine of the University of Columbia in the Americas said, “To our knowledge, this is the first basin-wide study to show that, contrary to what models suggest, photosynthesis actually increases under restricted water stress in some very humid regions of the Amazon rainforest.

“This increase is related to atmospheric dryness in addition to radiation, and can largely be explained by changes in the photosynthetic capacity of the canopy,” he said.

“When trees are stressed, they produce more efficient leaves that can more than compensate for the water stress.”

Machine learning methods have been used to analyze data from other climate models to assess how photosynthesis has been influenced by changes in soil moisture and air dryness in tropical regions of the Americas.

A comparable analysis was carried out, this time using observational data from satellite remote sensing to compare the findings.

Flux tower data, which monitors CO2 exchange rates between the Earth and the atmosphere around the globe, was then used to research processes on a smaller scale at the level of the canopy and leaf.

In previous studies, the greening of plants in parts of the Amazon basin was observed at the end of the dry season. Co-author Dr. Julia Green, who was a doctoral student at the time, said, “Prior to our study, it was still unclear whether these results were transferable to an effect over a larger region, and in addition to light, they had never been associated with air dryness.”

“Our results mean that current models are overestimating carbon losses in the Amazon rainforest due to climate change,” he said.

“So these forests in this particular region may actually be able to maintain or even increase photosynthetic rates if it gets a little warmer and drier in the future.”

That is, photosynthesis could slow down if drought were to rise above observed levels, because the researchers were only reviewing existing data.

“We found a tipping point for the most serious drought stress episodes, where the forest was unable to maintain its photosynthesis levels,” Ms. Green added.

“So our results are not an excuse for not reducing our carbon emissions.”

The researchers’ focus is now on measuring the effects of water stress on plant CO2 uptake and relating them to particular ecosystem characteristics.

Ms. Green said, “Much of the scientific research coming out these days assumes that our current ecosystems are unable to survive climate change, potentially causing global warming to accelerate due to feedback.”

“It was nice to see that some of our estimates of impending mortality in the Amazon rainforest may not be quite as bad as we previously thought.”

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