IT has been the subject of concern among environmentalists for decades as vast swathes of it disappeared to make way for human activity.

But the Amazon rainforest may not be on the brink after all – as some parts are more resistant to climate change than previously thought, according to new research.

Very wet areas in the Amazon, the world’s largest tropical rainforest, could actually benefit from slightly warmer temperatures, say scientists.

Forests absorb between 20 and 30 per cent of the carbon dioxide (CO2) we produce through photosynthesis, the chemical process plants use to make their food.

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

While previous research has warned climate change could accelerate as photosynthesis in water-stressed areas grinds to a halt, this may not be true for all parts of the forest.

In fact, the dry air could encourage plants in very wet regions to grow more efficient leaves, thereby increasing photosynthesis, the researchers say.

Study author Dr Pierre Gentine, of Columbia University in America, said: “To our knowledge, this is the first basin-wide study to demonstrate how, contrary to what models are showing, photosynthesis is in fact increasing in some of the very wet regions of the Amazon rainforest during limited water stress.

“This increase is linked to atmospheric dryness in addition to radiation and can be largely explained by changes in the photosynthetic capacity of the canopy.

“As the trees become stressed, they generate more efficient leaves that can more than compensate for water stress.”

Data from other climate models was analysed using machine learning techniques to determine how photosynthesis was affected by changes in soil moisture and air dryness across tropical regions of the Americas.

A similar analysis was carried out, this time using observational remote sensing data from satellites, so the results could be compared.

Data from flux towers, which monitor CO2 exchange rates between the earth and the atmosphere around the globe, was then used to study the processes on a smaller scale – at the canopy and leaf level.

The greenness of plants in parts of the Amazon basin at the end of the dry season has been observed in previous research. Co-author Dr Julia Green, who was a PhD student at the time, said: “Before our study, it was still unclear whether these results translated to an effect over a larger region, and they had never been connected to air dryness in addition to light.

“Our results mean the current models are overestimating carbon losses in the Amazon rainforest due to climate change.

“Thus, in this particular region, these forests may in fact be able to sustain photosynthesis rates, or even increase it, with some warming and drying in the future.”

That said, if dryness levels were to increase beyond the observed levels, photosynthesis could slow down, as the researchers only reviewed existing data.

Ms Green added: “We found a tipping point for the most severe dryness stress episodes where the forest could not maintain its level of photosynthesis.

“So our findings are certainly not an excuse to not reduce our carbon emissions.”

Measuring the effects of water stress on plant CO2 intake and relating them to specific ecosystem traits is now the researchers’ focus.

Ms Green added: “So much of the scientific research coming out these days is that with climate change our current ecosystems might not be able to survive, potentially leading to the acceleration of global warming due to feedbacks.

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