Climate Change, Deforestation, and the Fate of the Amazon

Environmental Change Institute, Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK.
Science (Impact Factor: 33.61). 02/2008; 319(5860):169-72. DOI: 10.1126/science.1146961
Source: PubMed


The forest biome of Amazonia is one of Earth's greatest biological treasures and a major component of the Earth system. This
century, it faces the dual threats of deforestation and stress from climate change. Here, we summarize some of the latest
findings and thinking on these threats, explore the consequences for the forest ecosystem and its human residents, and outline
options for the future of Amazonia. We also discuss the implications of new proposals to finance preservation of Amazonian

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Available from: Yadvinder Malhi,
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    • "Because tropical forests are already affected by other major local and global issues. They represent a reserve of land with potential for agriculture, mining resources, various timber and non-timber resources in areas of high population growth (Malhi et al. 2008). The diversity of threats is the main problem for tropical forests. "
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    ABSTRACT: Tropical forests account for over 50 % of the global forested area and forest carbon stock. Although the deforestation rate is tending to decline, forests are confronted with climate change, which could profoundly modify their functioning. The migration of species that took place during the Pleistocene is no longer possible because human activities have markedly altered tropical landscapes. Forest species will thus have to adapt (or not) particularly to the increased water stress. Forest management methods must incorporate new knowledge on the vulnerability of species and evolve in order to reduce potentially negative interactions between disturbances and the water deficit. A key challenge is to identify trade-offs between logging in water deficit situations and the increased forest fire risk. In drylands, factors related to climate change are meshed with other change factors, but innovations in the management of woodlands could ensure their long-term persistence.
    Climate Change and Agriculture Worldwide, Editions Quae edited by Emmanuel Torquebiau, 01/2016: chapter 14: pages 183-196; Springer., ISBN: 9789401774628
    • "These findings are consistent in their sign with prior work, but the overall magnitude of precipitation change is relatively small in our simulations, despite significant changes in convective instability and available energy. Future climate change is expected to bring drier conditions to the Amazon basin (Malhi et al., 2008, 2009; Joetzjer et al., 2013). If, as we expect, deforestation occurs superimposed on a background state of drying, we postulate that drying feedback associated with the loss of transpiring trees could accelerate the movement across a convective threshold to more severe reductions in rainfall. "
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    ABSTRACT: Ongoing agricultural expansion in Amazonia and the surrounding areas of Brazil is expected to continue over the next several decades as global food demand increases. The transition of natural forest and savannah ecosystems to pastureland and agricultural crops is predicted to create warmer and drier atmospheric conditions than the native vegetation. Using a coupled ecosystem regional atmospheric model (EDBRAMS) we investigate the expected impacts of predicted future land use on the climate of South America. The climate response in the model simulations is generally consistent with expectations from previous global modeling simulations with drier conditions resulting from deforestation, however the changes in precipitation are relatively small (on order of a few percent). Local drying is driven primarily by decreases in evapo-transpiration associated with the loss of forest, and concomitant increases in runoff. Significant changes in convectively available potential energy (CAPE) and convective inhibition (CIN) during the transition to the wet season indicate that the decrease in surface latent heat flux is indeed leading to a drier atmosphere, however these changes occur around a mean climatological state that is already very favorable for convection, and thus lead to relatively small changes in precipitation. If, however, these land use changes were to occur under a background state of drier conditions, such as those predicted for the future global climate model experiments, this additional atmospheric drying may be sufficient to decrease precipitation more substantially.
    Agricultural and Forest Meteorology 12/2015; 214-215:12-24. DOI:10.1016/j.agrformet.2015.07.006 · 3.76 Impact Factor
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    • "Recent drought events in the region have been linked to increased rates of tree mortality (Phillips et al., 2009; Lewis et al., 2011) and increased fire occurrence (Arag~ ao et al., 2007). Several GCM projections predict that, especially under the SRES A2 emission scenario, significant rainfall reductions will occur in eastern Amazonia over the coming century, with the steepest declines occurring during the dry season months (Malhi et al., 2008) and that dry season length and intensity will increase (Malhi et al., 2009; Costa & Pires, 2010), amplifying the occurrence of wet and dry months (Lintner et al., 2012). A number of modeling studies using global dynamic vegetation models predict Correspondence: Paul R. Moorcroft, tel. "
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    ABSTRACT: The Amazonian tropical evergreen forest is an important component of the global carbon budget. Its forest floristic composition, structure and function are sensitive to changes in climate, atmospheric composition and land use. In this study biomass and productivity simulated by three DGVMs (IBIS, ED2 and JULES) for the period 1970–2008 are compared with observations from forest plots (RAINFOR). The spatial variability in biomass and productivity simulated by the DGVMs is low in comparison to the field observations in part because of poor representation of the heterogeneity of vegetation traits within the models. We find that over the last four decades the CO2 fertilization effect dominates a long-term increase in simulated biomass in undisturbed Amazonian forests, while land use change dominates a reduction in AGB, of similar magnitude to the CO2 biomass gain, in the south and southeastern Amazonia. Climate extremes exert a strong effect on the biomass on short time scales, but the models are incapable of reproducing the observed impacts of extreme drought on forest biomass. We find that future improvements in the accuracy of DGVM predictions will require improved representation of four key elements: 1) spatially variable plant traits; 2) soil and nutrients mediated processes; 3) extreme event mortality; 4) sensitivity to climatic variability. Finally, continued long-term observations and ecosystem-scale experiments (e.g. FACE experiments) are essential for a better understanding of the changing dynamics of tropical forests.
    Global Biogeochemical Cycles 11/2015; DOI:10.1002/2015GB005135 · 3.97 Impact Factor
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