For years climate skeptics have argued that increased levels of CO2 won’t be as severe as anticipated, as trees will grow bigger and faster in the presence of elevated CO2 thus increasing their capacity to sequester it. However, a study of the biomass dynamics of the Amazon rainforest published this week in Nature has put this argument to bed once and for all.
The 30 year study found that while trees are being seen to grow faster as CO2 levels increase, the rainforest has lost almost half its capacity to sequester and store CO2. This is on account of the fact that faster living is accompanied by earlier dying, and with trees dying younger than ever before their ability to act as a carbon sink is being diminished.
These findings, of over 100 researchers led by a team in the University of Leeds, revealed that rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. The study focused on 321 forest plots comprising 200,000 trees, and recorded rates of tree deaths and growth and the appearance of new trees. The analysis indicates that the surge in the rate of trees dying across the Amazon is a consequence of growth stimulation from unprecedented elevations of atmospheric CO2.
According to lead author Dr Roel Brienen, ‘climate change models that include vegetation responses assume that as long as carbon dioxide levels keep increasing, then the Amazon will continue to accumulate carbon. Our study shows that this may not be the case and that tree mortality processes are critical in this system’.
This latest research contradicts the projections of many climate models in regard to vegetation, and undermines the assumption that our global forests will continue to act as a CO2 sink in the face of continued elevations.
With global pressure to reduce greenhouse gas emissions at an all-time high, this research adds to the barrage of evidence reinforcing the urgent need to take immediate action against human-induced climate change.