A process‐based investigation into the impact of the Congo basin deforestation on surface climate

Abstract

The sensitivity of climate to the loss of the Congo basin rainforest through changes in land cover properties is examined using a regional climate model. The complete removal of the Congo basin rainforest results in a dipole rainfall anomaly pattern, characterized by a decrease (∼−42%) in rainfall over the western Congo and an increase (∼10%) in the basin's eastern part. Three further experiments systematically examine the individual response to the changes in albedo, surface roughness, and evapotranspiration efficiency that accompany deforestation. The increased albedo (∼0.05) caused by the Congo basin rainforest clearance results in cooler and drier climate conditions over the entire basin. The drying is accompanied with a reduction in available surface energy. Reducing evapotranspiration efficiency or roughness length produces similar positive air temperature anomaly patterns. The decreased evapotranspiration efficiency leads to a dipole response in rainfall, similar to that resulting from a reduced surface roughness following Congo basin rainforest clearance. This precipitation anomaly pattern is strongly linked to the change in low-level water vapor transport, the influence of the Rift valley highlands, and the spatial pattern of water recycling activity. The climate responds linearly to the separate albedo, surface roughness, and evapotranspiration efficiency changes, which can be summed to produce a close approximation to the impact of the full deforestation experiment. It is suggested that the widely contrasting climate responses to deforestation in the literature could be partly due to the relative magnitude of change of the radiative and nonradiative parameterizations in their respective land surface schemes.

Data-driven estimates of evapotranspiration and its controls in the Congo Basin

“…As transpiration is the dominant component of ET throughout the Congo Basin (Lian et al, 2018), primary productivity (through its links to stomatal closure and active leaf area) likely explains the seasonality of ET wb to some degree. In fact, recent studies have found that evergreen forests in an equatorial section of the Congo exhibit a similar greenness seasonality to the seasonality of ET wb , with a bimodal cycle generally aligning with P but peaking in MAM instead of the wetter SON (Betbeder et al, 2014;Philippon et al, 2016). However, these studies focused on specific areas of evergreen forests and wetlands that may not represent the ecohydrology of the Congo Basin's entire equatorial rainforest belt and used MODIS products that do not fully account for sun-sensor geometry and other sources of error at low latitudes (Hilker et al, 2012;Bi et al, 2016).…”

Evaluation of simulations with the regional climate model REMO over Central Africa and the effect of increased spatial resolution

“…Panitz et al, 2014;Sylla et al, 2016) found that with modified parameterization of the soil albedo data, model can reduces bias. It is important to mention that the scarcity of observational data sets over forested areas is critical for characterizing model performance (Bell et al, 2015). Therefore, the model bias over that area should be interpreted with caution.…”

Global change effects on humid tropical forests: Evidence for biogeochemical and biodiversity shifts at an ecosystem scale

“…Within the tropics alone, large‐scale deforestation has been predicted to cause warming of 0.2°C [ Devaraju et al ., ]. Looking at tropical regions separately, total deforestation of the Amazon could increase regional temperatures by 0.8°C [ Lejeune et al ., ], and complete deforestation of the Congo basin could cause an even stronger warming response, raising local temperatures 2–3°C [ Bell et al ., ]. Clearly these numbers are upper estimates, since complete deforestation is unlikely.…”