Synergistic effects of drought and deforestation on the resilience of the south-eastern Amazon rainforest |
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Institution: | 1. Department of Geological Sciences, Stanford University, USA;2. Department of Physical Geography and Ecosystem Science, Lund University, Sweden;3. Center for Middle Eastern Studies, Lund University, Sweden;4. Department of Ecosystem and Landscape Dynamics, University of Amsterdam, Netherlands;5. Institute of Geosciences, Sect. Meteorology, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany;6. Institute of Earth Surface Dynamics, Geopolis, University of Lausanne, Switzerland;7. Department of Geosciences, University of Massachusetts, Amherst, USA |
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Abstract: | The south-eastern Amazon rainforest is subject to ongoing deforestation and is expected to become drier due to climate change. Recent analyses of the distribution of tree cover in the tropics show three modes that have been interpreted as representing alternative stable states: forest, savanna and treeless states. This situation implies that a change in environmental conditions, such as in the climate, could cause critical transitions from a forest towards a savanna ecosystem. Shifts to savanna might also occur if perturbations such as deforestation exceed a critical threshold. Recovering the forest would be difficult as the savanna will be stabilized by a feedback between tree cover and fire. Here we explore how environmental changes and perturbations affect the forest by using a simple model with alternative tree-cover states. We focus on the synergistic effects of precipitation reduction and deforestation on the probability of regime shifts in the south-eastern Amazon rainforest. The analysis indicated that in a large part of the south-eastern Amazon basin rainforest and savanna could be two alternative states, although massive forest dieback caused by mean-precipitation reduction alone is unlikely. However, combinations of deforestation and climate change triggered up to 6.6 times as many local regime shifts than the two did separately, causing large permanent forest losses in the studied region. The results emphasize the importance of reducing deforestation rates in order to prevent a climate-induced dieback of the south-eastern Amazon rainforest. |
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Keywords: | Bistability Climate change Critical transitions Fire Regime shifts Tipping points |
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