Modeled Response of South American Climate to Three Decades of Deforestation

Abstract

This study investigates the potential effects of historical deforestation in South America using a regional climate model driven with reanalysis data. Two different sources of data were used to quantify deforestation during 1980-2010s, leading to two scenarios of forest loss, smaller but spatially continuous in Scenario 1 and larger but spatially scattered in Scenario 2. The model simulates a generally warmer and drier local climate following deforestation. Vegetation canopy becomes warmer due to reduced canopy evapotranspiration, and ground becomes warmer due to more radiation reaching the ground. The warming signal for surface air is weaker than for ground and vegetation, likely due to reduced surface roughness suppressing the sensible heat flux. For surface air over deforested areas, the warming signal is stronger for the nighttime minimum temperature and weaker or even becomes a cooling signal for the daytime maximum temperature, due to the strong radiative effects of albedo at midday, which reduces the diurnal amplitude. The drying signals over deforested areas include lower atmospheric humidity, less precipitation, and drier soil. The model identifies the La Plata basin as a region remotely influenced by deforestation, where a simulated increase of precipitation leads to wetter soil, higher ET, and a strong surface cooling. Over both deforested and remote areas, the deforestation-induced surface climate changes are much stronger in Scenario 2 than Scenario 1; coarse resolution data and models (such as in Scenarios 1) cannot represent the detailed spatial structure of deforestation and underestimate its impact on local and regional climates.

Active Fire Dynamics in the Amazon: New Perspectives From High‐Resolution Satellite Observations

“…Tree mortality due to drought and deforestation allows sunlight to penetrate clearings in the canopy, making the surface environment drier and more flammable (Ray et al., 2005). Therefore, we emphasize that local drought favors the spread of fire and determines whether ignitions grow into catastrophic fires (Jiang et al., 2021; Wang et al., 2011). Although local governments have made efforts to ban logging and burning in the dry season, the human‐associated fire occurrences indicate the growing risk of continued forest degradation at the agriculture–forest interface, which should be targeted as a priority conservation area to prevent fires escaping from nearby farmlands into forests.…”

Variability, Trend, and Extremes of the South American Vegetation‐Climate System: Results From a Coupled Regional Model

“…To some degree, the spatial pattern of ET biases resembles that of the precipitation biases in all four seasons and bears little similarity to vegetation LAI biases (except for the northeast costal area where both precipitation and ET as well as vegetation are underestimated). This results from an overall weak influence of vegetation on total ET, a result of a strong compensating effect by ground evaporation when plant evapotranspiration is altered (Jiang et al., 2021).…”

Drought–heatwave nexus in Brazil and related impacts on health and fires: A comprehensive review

“…In particular, the influence of deforestation-induced feedback on the occurrence, intensity, and frequency of CDHW events should be further investigated, given the observed influence of Amazonia land cover changes on surface temperature, the energy budget, and the hydrological cycle. 194 Additionally, the direct impacts of hot and dry compound events on the forest ecosystem are not yet documented over the region, although studies have reported changes in Amazonia forest productivity related to drought frequencies and warming trends. 105,106,188 The Cerrado savannas By contrast to the other biomes referred to in this section, the Cerrado is no stranger to fire.…”

“…Other factors can also influence fire activity and may contribute to some of the variability that is not explained by climate extremes, for instance, anthropogenic factors, including political and economic drivers, 191 but also natural factors, such as soil moisture content, 188 and positive fire–climate 192 and deforestation–climate 193 feedbacks. In particular, the influence of deforestation‐induced feedback on the occurrence, intensity, and frequency of CDHW events should be further investigated, given the observed influence of Amazonia land cover changes on surface temperature, the energy budget, and the hydrological cycle 194 . Additionally, the direct impacts of hot and dry compound events on the forest ecosystem are not yet documented over the region, although studies have reported changes in Amazonia forest productivity related to drought frequencies and warming trends 105,106,188 …”