Stability and resilience of tropical vegetation transitions

There is growing evidence that tipping elements exist in both the climate system and on ecosystems. The terrestrial ecosystems where regime shifts are most likely to have powerful repercussions on the Earth system are the vast tropical forest and savanna biomes. The zone of transition between tropical forests and savannas is a zone of ecological tension (ZOT): on one hand, there is growing evidence that climate change (expressed as an increase on average temperature, CO2 atmospheric concentration, and total annual rainfall) is favouring the forest expansion into the savanna. Increases in tree density in savannas will significantly alter their ecosystem functioning and diversity and will reduce their economic profit (yields, cattle). One the other hand, disturbances associated to global change (being extreme drought events, logging and fires the most outstanding) are favouring forest dieback and the savannization process. Forest dieback will have very important consequences on global carbon balance, biodiversity, and climate feedbacks. However, the uncertainty in how climate and land use change will change in these regions, coupled with the uncertainty the mechanisms driving change, hampers our ability to predict change.