Tree survival depends on what the scientists call 'leaf economics': their different size, thickness, longevity or density defines how well the plant can deal with higher temperatures and water scarcity. "Biodiversity shows not to be a nice-to-have but indeed a must-have," Sakschewski continues. "We find it could be functional for the long-term survival of Earth's large reservoirs of biomass, such as the forests of the Amazon region."
However, this also depends on the stress level. Only in a scenario of moderate climate change, but after a sharp decline of biomass, could biodiversity contribute to substantial recovery in large areas across the Amazon region - after a few hundred years. The simulations reveal that more than 80 percent of the Amazon area would show substantial regrowth. In contrast, in a business-as-usual scenario of greenhouse-gas emissions leading to massive climate change, less than 20 percent of the area would experience this postive outcome.
This result is a significant step forward in Earth system modelling. "To explain how plant trait diversity contributes to the resilience of rainforests, we first investigated an experimental site in Ecuador and then extended the simulations to the Amazon basin," explains team leader Kirsten Thonicke. "We've been working on this for years. While it is well-known that biodiversity is relevant for ecosystem productivity and biomass storage, up to now it could not be shown in a large-scale quantitative way. We're glad to advance previous research by closing this gap."
"This is good news for the Amazon forest – still, it doesn't mean that climate change would not harm this unique ecosystem substantially, quite the contrary," says Wolfgang Lucht, co-chair of PIK's research domain Earth System Analysis. While high biodiversity enables the forest to eventually regain much of its biomass, there is a huge disruption in the transition, and the species composition would be different afterwards even under moderate global warming. "Despite the encouraging findings on biodiversity's functional value, the Amazon rainforest unfortunately remains one of the critical hotspots on the planet that demand very rapid decreases in CO2 emissions."
(© Potsdam Institute for Climate Impact Research PIK, AcademiaNet)