Trees offer surprising climate benefit

Microbes in tree bark absorb methane, say scientists at the University of Birmingham, UK.

Soil was previously considered the only terrestial methane sink, but this research concludes that trees may be be just as important, or even more so.

This surprising climate benefit, in addition to trees removal of carbon dioxide, is reported as equal to or above the scale of methane removal by soil.

The team says methane is responsible for around 30% of global warming since pre-industrial times, with emissions currently rising faster than at any point since records began in the 1980s.

Lead researcher Professor Vincent Gauci says, 'The Global Methane Pledge, launched in 2021 at the COP26 climate change summit, aims to cut methane emissions by 30% by the end of the decade. Our results suggest that planting more trees and reducing deforestation surely must be important parts of any approach towards this goal.'

The team investigated upland tropical, temperate and boreal forest trees. They took measurements from tropical forests in the Amazon and Panama, temperate broadleaf trees in Wytham Woods in Oxfordshire, UK, and boreal coniferous forest in Sweden.

They conclude tropical forests to have the strongest methane absorption, probably due to microbes thriving in warm wet conditions.

The methane exchange between the atmostphere and tree bark was studied at multiple heights. At soil level, the trees were likely to emit a small amount of methane, but a couple of metres higher, the exchange switches and methane is consumed from the atmosphere.

The research group have also used laser scanning methods to quantify overall global borest tree bark surface area, with preliminary calculations indicating the total global contribution of trees to be 24.6-49.9Tg (millions of tonnes) of methane.

Interestingly, they also say the surface area of all tree bark is equal to the Earth's land surface. 

The team wants to investigate the microbes further, and find if the methane absorption can be enhanced.