Ecosystem Diversity and Heterogeneity Determine the Resilience of the Amazon to Climate Change

Abstract:

Amazon Forests, which play a vital role in global water, energy and carbon cycling, are predicted to experience both longer and more intensive dry seasons by the end of the 21^st century. However, the climate sensitivity of this ecosystem remains uncertain: several studies have predicted large-scale die-back of the Amazon, while several more recent studies predict that the biome will remain largely intact. In this study we use an individual-based terrestrial ecosystem model to explore the sensitivity and ecological resilience of these forests to changes in climate. Our results show that water stress operating at the scale of individual plants, combined with spatial variation in soil texture, strongly influence the ecosystem’s resilience to changes in dry season length. Further analysis shows that two key traits influencing the climatic sensitivity of individuals within the plant canopy are their phenology and hydraulic architecture. In contrast to existing predictions of either stability or catastrophic biomass loss, our analyses indicate that, as a result of these effects of ecosystem diversity and heterogeneity, the Amazon forest’s response to a drying regional climate is likely to be an immediate, graded, heterogeneous transition from high biomass moist forests to transitional dry forests and woody savannah ecosystems. While fire, logging and other anthropogenic disturbances may exacerbate the impacts of climate-induced changes, our analysis indicates considerable spatial variation in the vulnerability of Amazon forests to human induced climate change.