Impacts of Future Oil Palm Expansion on Carbon and Hydrological Fluxes across the Tropics

 

Oil palm plantation is a major form of land use and land cover change in the tropics, frequently occurring at the expense of natural vegetation and thereby altering carbon, water and energy fluxes. To assess the biophysical and biogeochemical impacts of future oil palm expansion under climate change, we developed a pan-tropical expansion scenario spanning from 2023 to 2100. Using CLM-palm, a perennial crop module based on the Community Land Model 5 (CLM5), we conducted oil palm expansion simulations for Southeast Asia, Africa and the Amazon under two climate scenarios (SSP1-2.6 and SSP3-7.0).

Across all regions, oil palm expansion increases total vegetation carbon (+9.7%) and net ecosystem production (more than fivefold), but reduces soil carbon (-5.9%) under the SSP1-2.6, reflecting trade-offs between productivity and long-term carbon storage. Vegetation carbon responses depend strongly on previous land use, with forest-to-oil palm conversion causing the largest losses and cropland conversions yielding modest gains. Hydrologically, expansion enhances evapotranspiration (+2.5%), leading to decreases in surface water availability (-3.3%), runoff (-3.3%) and soil moisture (-3.7%). Land surface temperature responses reflect competing  biogeophysical cooling (-0.54°C) and biogeochemical warming (+0.18°C), with strong regional contrasts: cooling in Africa (-0.37°C), warming in the Amazon (+0.23°C), and near offsets in Southeast Asia. Results under SSP3-7.0 show similar spatial patterns but substantially larger magnitudes, indicating that warming amplifies these responses.

These results show that oil palm expansion produces region-specific,  climate-dependent trade-offs in carbon, water and land surface temperature, underscoring the importance of accounting for land-use in climate assessments.