Plants take in less carbon in a warming world

As world temperatures rise, the rate at which plants in certain regions can absorb carbon dioxide is declining, according to University of Queensland research.

Over a three year period, the researchers took direct measurements of plant absorption of CO2 in subtropical coastal ecosystems in eastern Australia.

Professor Hamish McGowan, from UQ’s School of Earth and Environmental Sciences, said the team found the optimum temperature for photosynthetic production was routinely exceeded in these regions.

“Plants’ optimum temperature range for photosynthesis in our study area is between 24.1 and 27.4 degrees Celsius,” Professor McGowan said in a statement. “But due to anthropogenic climate change, temperatures – particularly in warmer months – often go well beyond this ‘healthy’ range for carbon absorption.”

Temperatures exceeded this range between 14 and 59.2 per cent of the time, depending on the site, he highlights. The result is that plants cannot absorb carbon at the rates they used to.

The research team also measured the rate at which photosynthesis was occurring, with alarming results. “We are seeing through observational evidence that a dangerous positive feedback loop is being created, making the world even hotter,” continued Professor McGowan.

The effects of a changing climate on rainfall in subtropical ecosystems are compounding the issue. “While future warming will cause rainfall in some tropical regions to increase, in the subtropics and Mediterranean climate zones it is likely to decrease,” he said. “This inevitably leads to reduced growth and increased risk of tree mortality, reducing even further these areas’ potential to sequester carbon dioxide.”

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