Climate change will increase savannas at the expense of forests and treeless vegetation in tropical and subtropical Americas

Abstract

Summary 1.Transition areas between biomes are particularly sensitive to environmental changes. Our understanding of the impacts of ongoing climate change on terrestrial ecosystems has significantly increased during the last years. However, it is largely unknown how climatic change will affect transitions among major vegetation types. 2. We modelled the distribution of three alternative states (forest, savanna and treeless areas) in the tropical and subtropical Americas by means of climate-niche modelling. We studied how such distribution will change by the year 2070 by using 17 downscaled and calibrated global climate models from the Coupled Model Intercomparison Project Phase 5 and the latest scenarios provided by the 5th Assessment Report of the IPCC. 3. Our results support the savannization of the tropical and subtropical Americas because of climate change, with an increase in savannas mainly at the expense of forests. 4. Our models predict an important geographical shift in the current distribution of transition areas between forest and savannas, which is much less pronounced in the case of those between savannas and treeless areas. Largest shifts, up to 600 km northward, are predicted in the forest-savanna transitions located in the eastern Amazon. 5. Our findings indicate that climate change will promote a shift towards more unstable states: the extent of the transition areas will notably increase, and largely stable forest areas are predicted to shrink dramatically. 6. Synthesis. Our work explores dimensions of the impact of climate change on biomes that have received little attention so far. Our results indicate that climate change will not only affect the extent of savanna, forest and treeless areas in the tropical and subtropical Americas, but also will: (i) promote a significant geographical shift and an increase of the extent of transition areas between biomes and (ii) decrease the stability of the equilibrium between forest, savanna and treeless areas, yielding a more unpredictable system.

Evolution of Cerrado Vegetal Cover on a River Island Based on Orbital Imaging Data

“…The increase in Forest complex areas during the study period disagrees with results obtained by other authors in arid regions around the world, in which the forest covers have been turning into savanna physiognomies (MISHRA et al, 2015;GRECCHI et al, 2014;MÜLLER et al, 2015;HIROTA et al, 2011;ROCHA et al, 2011). ANADÓN et al (2014) explained that changes in landscape and regional weather might increase transitional vegetation in biomes. This process may be related to the presence of forest formations in Cerrado areas with deep, fertile and moist soils (HENRIQUES, 2005), as it is observed in Red Latosols of the studied EEP, as well as fighting fires (DURIGAN & RATTER, 2006).…”

“…Therefore, only to surround and protect the natural areas of Cerrado broad sensu is not enough against the influence of fire. This protection likely will result in environmental imbalance; and the ecosystem will possibly evolve into a different condition of the original one (ANADÓN et al, 2014;DURIGAN & RATTER, 2006).…”

Woody Plant Encroachment: Causes and Consequences

“…In the future, if climate becomes warmer and drier or if the frequency, magnitude, and duration of drought increase, present-day grasslands in some areas may become desert shrubland. In contrast, woodlands and forests could also shift to savanna or grassland (e.g., Allen et al 2010;Anadón et al 2014a) and increases in woody cover realized in recent decades may be reduced by a higher frequency of "hot droughts" (Bowers 2005;Breshears et al 2005;Twidwell et al 2014). Climatechange simulations under elevated atmospheric CO 2 predict pronounced shifts toward tree-dominated biomes (Scheiter and Higgins 2009).…”

Climate seasonality, fire and global patterns of tree cover

“…Changes in extrinsic environmental conditions such as climate and fire cycles may remove or add barriers that limit establishment of trees and in particular of invasive tree species Bond 1991, Scholes andArcher 1997). Vegetation structure and total tree cover of a region may change as a consequence of climatic changes (Anadón et al 2014, Rundel et al 2014 leading to losses of species habitat, new species assemblages, changes in nutrient and water cycles and cascading implications for ecosystem functioning and biodiversity (Parr et al 2012). In addition, established tree species, whether native or non-native, sometimes have the capacity to modify the environment in ways that favor their own recruitment (Scholes and Archer 1997) reinforcing the persistence of the new tree cover state.…”