Recent and projected impacts of land use and land cover changes on carbon stocks and biodiversity in East Kalimantan, Indonesia

Large-scale land use and land cover (LULC) changes can have strong impacts on natural ecosystems, such as losses of biodiversity and carbon. Future impacts, under one or multiple future scenarios, can be estimated with the use of LULC projections from land use change models. Our aim is to quantify LULC change impacts on carbon stocks and biodiversity in the West Kutai and Mahakam Ulu districts in East Kalimantan, Indonesia. Hereto, we used LULC data from 1990 to 2009 and land use change model projections up to 2030 under four contrasting LULC change scenarios differing along two axes: land development (limited vs. unlimited) and zoning (restricted vs. unrestricted), explicitly considering the uncertainties in the land use change model. For the LULC change impact calculations, three quantitative indicators were evaluated: aboveground biomass (AGB) (for carbon stocks), closed-canopy forest patch size distribution and plant species richness (for biodiversity). Subsequently, we statistically assessed whether the motivation to opt for a specific scenario was conclusive given the uncertainty in the indicator values. We found that under the limited development scenarios the projected AGB decrease towards 2030 was insignificant, plant species richness was projected to decrease significantly by similar to 3%, and closed-canopy forest patches mainly of 100-1000 ha were projected to become fragmented. The effect of zoning was insignificant under these scenarios. The difference between the limited and unlimited development scenarios was significant, with the projected impacts under the unlimited development scenarios being much higher: AGB was projected to decrease 4-30%, plant species richness 10-40%, and the closed-canopy forest was projected to completely loose its typical patch size distribution. The effect of zoning on these scenarios was positive and significant. These results suggest that the most sustainable pathway for East Kalimantan, given our indicators, would be to limit land development, mainly large-scale cash-crop cultivation. If land development cannot be limited, the implementation of restricted development zones is advised. The methodologic novelty of our approach is that we propagate uncertainties from a land use change model to the impact assessment and test the significance of differences between future scenarios, in other words we test if a potential policy instrument has a significant (positive) effect on the studied indicators and may thus be worth implementing.