The research was based around a simple mathematical model created by the scientists to predict how ecosystems would respond to rising temperatures. The model was based on just two parameters: the ‘activation energies’ for photosynthesis and respiration. ‘Photosynthesis by plants absorbs CO2, while respiration by animals returns CO2 to the atmosphere,’ Gabriel Yvon-Durocher, the study’s lead author, explained. ‘Respiration has a higher activation energy than photosynthesis, meaning that it increases more rapidly with increasing temperature.

So if climate change raises environmental temperatures, the balance between respiration and photosynthesis in the ecosystem will change, favouring more respiration and less CO2 absorption.’

The scientists tested their model’s predictions against data collected from a series of experimental ponds that were warmed by 4°C to simulate the rise predicted to take place by 2100. They found a 13 per cent reduction in the amount of CO2 absorbed by the warmed ecosystems.

The results are backed up by as-yet-unpublished data collected by scientists at the Macaulay Land Use Research Institute in Aberdeen from streams of varying temperatures in Iceland, which has shown that the warmer streams emitted far more CO2 than the cooler streams, acting as sources of carbon rather than sinks.

September 2010