Impacts of future deforestation and climate change on the hydrology of the Amazon basin: a multi-model analysis with a new set of land-cover change scenarios

Abstract

Abstract. Neglecting any atmospheric feedback to precipitation, deforestation in Amazon, i.e., replacement of trees by shallow rooted short vegetation, is expected to decrease evapotranspiration (ET). Under energy-limited conditions, this process should lead to higher soil moisture and a consequent increase in river discharge. The magnitude and sign of the response of ET to deforestation depends both on land-cover change (LCC), and on climate and CO2 concentration changes in the future. Using three regional LCC scenarios recently established for the Brazilian and Bolivian Amazon, we investigate the combined impacts of deforestation and climate change on the surface hydrology of the Amazon basin for this century at sub-basin scale. For each LCC scenario, three land surface models (LSMs), LPJmL-DGVM, INLAND-DGVM and ORCHIDEE, are forced by bias-corrected climate simulated by three General Circulation Models (GCMs) for different scenarios of the IPCC 4th Assessment Report (AR4). The GCM results indicate that by 2100, without deforestation, the temperature will have increased by a mean of 3.3 °C (a range of 1.7 to 4.5 °C) over the Amazon basin, intensifing the regional water cycle, whereby precipitation, ET and runoff increase by 8.5, 5.0 and 14 %, respectively. However, under this same scenario in south-east Amazonia, precipitation decreases by 10 % at the end of the dry season and the three LSMs estimate a 6 % decrease of ET, which does not compensate for lower precipitation. Runoff in southeastern Amazonia decreases by 22 %, reducing minimum river discharge from the Rio Tapajós catchment by 31 % in 2100. The low LCC scenario projects a 7 % decline in the area of Amazonian forest by 2100, as compared to 2009; for the high LCC scenario the projection is a 34 % decline. In the extreme deforestation scenario, forest loss partly offsets (−2.5 %) the positive effect of climate change on increasing ET and slightly amplifies (+3.0 %) the increase of runoff. Effects of deforestation are more pronounced in the southern part of the Amazon basin, in particular in the Rio Madeira catchment where up to 56 % of the 2009 forest area is lost. The effect of deforestation on water budgets is more severe at the end of the dry season in the Tapajós and the Xingu catchments where the decrease of ET due to climate change is amplified by forest area loss. Deforestation enhances runoff during this period (+35 %) offsetting the negative effect of climate change (−22 %), and balances the decrease of low flows in the Rio Tapajós.

Novel Representation of Leaf Phenology Improves Simulation of Amazonian Evergreen Forest Photosynthesis in a Land Surface Model

“…The modeled carbon processes include phenology, photosynthesis, respiration, allocation, and leaf shedding (Figure 2 in Krinner et al, ). The standard ORCHIDEE version (v8.4.1) used here was recently evaluated over high latitudes (Guimberteau et al, ; Guimberteau et al, ). Because the model is known to perform poorly for tropical phenology (De Weirdt et al, ; Sitch et al, ; Peng et al, ); we investigated the canopy phenology of tropical evergreen forests aiming to improve the modeling of the processes of leaf growth and leaf shedding in the ORCHIDEE.…”

Larval diet of twoAmazoniangoliath catfish species

“…The consumption of larval and adult insects by B. rousseauxii and B. filamentosum show the relevance of both autochthonous and allochthonous resources during the larval stages of these species. These migratory fish suffer stresses not only because to dam construction impedes migration and changes the impact of fisheries (Anderson et al ., 2018; Lima et al ., 2020b), but also because anthropogenic change from deforestation of riparian forests (Trancoso et al ., 2009), mining activity (Finer et al ., 2008) and climate change can have important effects altering the autochthonous and allochthonous inputs, and thus the aquatic food webs (Guimberteau et al ., 2017).…”

New generation geostationary satellite observations support seasonality in greenness of the Amazon evergreen forests

“…Amazon forests have a strong influence on global climate, carbon, and water cycles. Understanding the interactions of Amazon forests with the climate system is a key to predicting climate changes in the 21st century 1 , 2 . For instance, severe Amazon droughts are expected to occur more frequently as a result of global warming 3 , 4 and modeling forests’ responses to drought is crucial for climate projections 5 .…”