Abstract
Deforestation and climate change are interconnected and represent major environmental challenges. Here, we explore the capacity of regional-scale restoration of marginal agricultural lands to savanna woodlands in Australia to reduce warming and drying resulting from increased concentration of greenhouse gases. We show that restoration triggers a positive feedback loop between the land surface and the atmosphere, characterised by increased evaporative fraction, eddy dissipation and turbulent mixing in the boundary-layer resulting in enhanced cloud formation and precipitation over the restored regions. The increased evapotranspiration results from the capacity deep-rooted woody vegetation to access soil moisture. As a consequence, the increase in precipitation provides additional moisture to soil and trees, thus reinforcing the positive feedback loop. Restoration reduced the rate of warming and drying under the transient increase in the radiative forcing of greenhouse gas emissions (RCP8.5). At the continental scale, average summer warming for all land areas was reduced by 0.18 oC from 4.1 oC for the period 2056–2075 compared to 1986–2005. For the restored regions (representing 20% of Australia), the averaged surface temperature increase was 3.2 °C which is 0.82 °C cooler compared to agricultural landscapes. Further, there was reduction of 12% in the summer drying of the near-surface soil for the restored regions.
Highlights
A number of studies using climate models have investigated the potential climate impacts of reforestation and afforestation[21,22,23,24,25,26]
The development of land-use scenarios is supported by recent assessments of the future land use options for Australia based on the evaluation of sustainability of economic returns and provision of ecosystem services[35,36,37]
Using land-use scenarios and the high-emission RCP8.5 scenario, we demonstrate that regional-scale restoration has the capacity to moderate the warming and drying at the regional scale
Summary
A number of studies using climate models have investigated the potential climate impacts of reforestation and afforestation[21,22,23,24,25,26]. A global study by Arora and Montenegro[23] of the climate impact of complete and partial (50%) afforestation of croplands resulted in a reduction of warming of 0.45 °C and 0.25 °C respectively for the period 2081–2100 under the SRES A2 emissions scenario. Galos[26] used a regional climate model under the SRES A2 scenario to show that afforestation reduced warming of summer temperatures by 15–20% and halved the rainfall reduction due to global warming in the mid-latitude of Central Europe. We use a high-resolution climate model to better resolve the influence of the spatial heterogeneity of soils and vegetation on regional climate processes. We focus on Australia, as a representative semi-arid region with highly-transformed landscapes[28] and large areas of economically marginal agricultural land[29]. A recent economic analysis of future land use options for Australia shows that large areas of economically marginal agricultural lands would have better economic and environmental return if used for carbon sequestration and other related ecosystem services[35,36]
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