Abstract

At a time of heightened concern at the pace of human-caused climate change and its impacts on humanity and the biosphere, one of the key concerns is evaluating how close the Earth System is to “tipping points”, where biophysical feedbacks start accelerating climate change feedbacks. One of the most iconic of these tipping points is the potential dieback of tropical forests, which change regional climate and release substantial carbon dioxide to the atmosphere. While possible tropical forest dieback has been the focus on many modelling studies, there have been a dearth of field-based empirical studies looking at the effects of climate extreme events on the tropical forest carbon cycle at global scale. Here we examine this issue by exploring the impacts of the strong 2015/6 El Nino event on a pan-tropical set of forest carbon cycle monitoring plants within the Global Ecosystems Monitoring (GEM) network. The impacts of the El Nino were strongest in eastern Amazonia, where the dominant effect in intact forests was was a large release of carbon dioxide from soils. However, substantial areas of forest in eastern Amazonia also caught fire, leading to large scale tree mortality and longer term forest degradation and carbon emission. Such fires have been increasing in extent as Amazonian climate warms dries, and the interaction between forest fragmentation, climate change and fire poses the greatest threat to causing substantial loss of Amazonian forest. Conversely, fire management interventions may help to minimise the risk of a tropical forest tipping point under climate change.