Introduction climate change and land use change in amazonia

1. Introduction

Global warming due to increased greenhouse gas emissions by human activities and natural climate change presents a challenge for the world’s natural ecosystems. The acceleration of human-driven climate change poses serious questions and challenges for conservation strategies to cope with the expected changes in the distribution, physiology and ecology of most species. This is especially true for the tropical forests with its tremendous species diversity. Several studies have discussed the future of the Amazon Osborn et al., 2011; Soares-Filho et al., 2010; Lapola et al. 2010; Gómez and Nagatani et al., 2009; Malhi et al., 2008; Aguiar, 2006; Soares-Filho et al., 2006; Laurance et al., 2001 in the wake of global concerns about biodiversity loss, deforestation-driven CO 2 emissions through the intensification of droughts and vulnerability to forest fires and intense land use and land cover changes. The ecosystems of Amazonia are subjected to two different, but interconnected, climatic driving forces: one is regional deforestation and land use change such as biomass burning and forest fragmentation, which affects local and regional climate, and the second is global climate change Salati et al., 2006, IPCC 2007, SREX 2012. Many studies indicate that both of these changes in climate will contribute to regional increases in temperature. However, uncertainties are still considerably high for projections of regional changes of the hydrological cycle e.g., Li et al., 2006, IPCC 2007, Marengo et al 2009 and thus changes in precipitation patterns are more difficult to determine. The Amazonia region holds the largest contiguous tropical forest on the planet. The vegetation, including its deep root system, is efficient in recycling water vapour, acting as an important mechanism not only for the forest’s maintenance, but also for the water flows in the region, possibly regulating regional climate [Spracklen et al., 2012; Werth and Avissar, 2002]. In principle, deforestation and global warming acting synergistically could lead to drastic biome changes in Amazonia. Oyama and Nobre 2003 have shown that two stable vegetation-climate equilibrium states are possible in Tropical South America. One equilibrium state corresponds to the current vegetation distribution where tropical forest covers most of the Basin. The other equilibrium state corresponds to a land cover in which most of the eastern Amazonia is covered by scarce vegetation, with more open canopy and more drought resistant species. It is not a trivial scientific question to find out at which point the current stable state could switch perhaps abruptly to the second state, given the combined forcing of land use and cover change e.g. deforestation, forest fragmentation, increased forest fire and global warming with a likely consequence of more intense droughts such as the severe drought which affected the region in 2005 and 2010; Marengo et al 2008, 2011a, b, c, Zeng et al 2008, Tomasella et al., 2010, 2012. Some model projections Cox et al., 2004, Oyama and Nobre, 2004, Salazar et al., 2007, Betts et al., 2008, Sitch et al., 2008, Salazar et al., 2010 show over the next few decades this risk of abrupt and irreversible change in vegetation structure in the region, with large-scale loss of biodiversity and pressure on livelihoods. This process is referred to as the “die-back” of the Amazon forest, which occurs after reaching a “tipping point” in regional climate e.g. air temperature or in deforested area e.g. beyond 40 of forest cover loss, according to Sampaio et al., 2007. If the current pace of change land cover and climate remains unaltered we may well only find out that the “climate-vegetation” equilibrium has been reached after we have passed the threshold for its establishment. Temperature increases and disruption in the energy and water cycles have the potential to seriously hamper the functioning of the Amazon as a forest ecosystem, reducing its capacity to retain carbon, increasing its soil temperature, and eventually affecting the regional hydrological cycle. In simple terms, the increase in temperature induces larger evapotranspiration in tropical regions which tends to reduce the amount of soil water, even when rainfall does not reduce significantly. This can trigger the replacement of the present-day vegetation by other vegetation types more adapted to drier conditions. If severe droughts become more frequent in the future, which is a common projection for a warmer planet, eastern Amazonia would experience more dramatic changes in vegetation type cover, since the models simulate a higher probability for that area to face frequent and intense droughts Hutyra et al., 2005. Land cover and land use change are, per se, strong pressures over natural systems. On the other hand, the Amazon in South America is home to more than 40 million people, which, despite intense urbanization, still live and depend on the region’s natural resources. The Amazon is a heterogeneous and complex landscape, where multiple forces can potentially contribute to changes in land use and cover e.g. deforestation. Global markets pressure for food and biofuels Brasil, 2012; Foley et al., 2011; Lambin and Meyfroidt, 2011; Lapola et al., 2010, new transportation and energy infrastructure projects Brasil, 2011 and weak institutions Vieira et al., 2008, can be cited as some of key drivers in this process. In this report we present a literature review of different Land Use and Cover Change scenarios for the Amazon, with a focus on Bolivia, Brazil, Colombia, Ecuador and Peru Figure 1. A short summary discusses the information available and highlights any research gaps related to climate change and land use and cover change scenarios. We also review current knowledge on climate variability and climate change in the region, considering its possible effects and feedback with land use and land cover change. The occurrence of extreme climate events, linked to extremes in natural climate variability, is also discussed. Figure 1: Study area

2. Land Use Change