Title: Land Use, Land Use Change and Forestry activities for Climate Change Mitigation
Other Titles: Landgebruik, veranderingen in landgebruik en bosbouwactiviteiten voor het tegengaan van klimaatverandering
Authors: Trabucco, Antonio
Issue Date: 6-Dec-2012
Abstract: An effective cutback of atmospheric carbon can be implemented through land-use, land-use change and forestry (LULUCF) activities, by increasing the biomass in terrestrial ecosystems or entailing production of biofuels. However the adoption of new LULUCF activities may lead to trade-offs with other ecosystem services. The assimilation of modeling tools with available global geodatasets can assist more effectively the promotion of such LULUCF activities, assessing their effective opportunity potential and associated trade-off with other ecosystem services. To accomplish this task, we evaluate the biophysical suitability and trade-off at global scale of two selected LULUCF strategies to reduce atmospheric carbon concentration: · Afforestation/Reforestation (AR) activities, to increase ecosystem carbon stocks, financed and regulated within the Kyoto Protocol by the Clean Development Mechanism afforestation and reforestation activities (CDM-AR). · Jatropha biofuel crops, to curb carbon emission from fossil fuel use, claimed to have biofuel potential in semiarid regions where competition with food production and other ecosystem services is limited in comparison to other biofuel crops. The spatial suitability distribution of the selected LULUCF activities was defined following two different approaches at high resolution. The first approach used a traditional land suitability analysis, a Multi Criteria Analysis based on relevant environmental geodatasets, to delineate land suitability of reforestation activities as for CDM-AR. Due to lack of scientific knowledge about Jatropha, a second approach used statistical inference (MaxEnt) to retrieve Jatropha productivity curves as a function of climate and turn them into Jatropha yield maps. For land use dynamics following LULUCF activities, we categorized specific impacts on water availability, climate change mitigation and food security. CDM-AR activities were found to be suitable globally on over 760 Mha of land. Although intensive agriculture has been excluded from land eligible for reforestation, rainfed cropland constitutes half of the suitable land (364 Mha globally). Savanna is extremely relevant among suitable land for reforestation in Sub-Saharan Africa (68%) and South America (40%) accounting for a total global extent of 296 Mha. Mixed/shrubland and grassland types add 63 Mha, while land suitability for reforestation over barren or sparsely vegetated land is very limited (about 2 Mha). The allowance for carbon emission reduction credits from CDM-AR activities can be fulfilled by only 4 to 8 Mha of land planted with fast growing tree species, which is equivalent to just 1 to 2% of all the grassland/shrubland/savanna suitable for reforestation worldwide. Under these conditions, optimal land uses choice for CDM-AR is widely available where impact on other ecosystem services is limited. A soil-water balance is used to estimate impacts resulting from reforestation activities with the objective of mapping changes in hydrology (vapor flow, excess water and soil water content). Large increases in AET and/or decreases in runoff are forecast from much of the areas deemed suitable for CDM-AR, if converted to forest. Of all the suitable land for reforestation, almost 20% (144 Mha) showed moderate impact on runoff (0-40% decrease in runoff). Carbon fixation through biomass production increases vapor flows, and requires consumption of water that may be temporarily not available for other uses. The strong hydrological impacts are more prevalent in drier areas, the semi-arid tropics, and pertain to conversion mostly from seasonal and scattered vegetation to extensive woody covers. The estimated suitable land for growing Jatropha biofuel accounts globally to 1,366 Mha. Most of this land is either forested (440 Mha) or intensive cropland (325 Mha). We found that substitution by Jatropha plantation of forest, tree mosaics and close shrubland causes an initial Ecosystem Carbon Debt that is much higher than the annual carbon emission reduction of Jatropha biofuel replacing fossil fuel use. Instead Ecosystem Carbon Gains are observed when Jatropha is planted on sparse herbaceous, bare areas and cropland. About 150 Mha of marginal land (herbaceous, bare and sparsely vegetated areas) are suitable for Jatropha farming, where impact on food production and ecosystem carbon stocks is generally limited. Overall biofuel production on all this marginal land may generate a biofuel production that can satisfy a small portion of the global fossil fuel demand (~ 1.5% of global oil consumption), which could drive Jatropha expansion where financially suitable to land use conflicts with other ecosystem services. Jatropha is found also climatically suitable over 268 Mha of shrubland, where land use change for Jatropha plantations can lead to moderate release of ecosystem carbon stocks. Also Jatropha farming is suitable over 154 Mha of mixed cropland systems characterized by subsistence or extensive agriculture. When Jatropha is adopted over cropland, trade-offs between food and energy security for human requirements are the lowest in Africa. Elsewhere the nutrient equivalent productivity of cropland is too high to justify any displacement of food crop for biofuel production. The inclusion of Jatropha crops over agricultural land could be in principle acceptable as a mean of agriculture intensification in Africa where agricultural productivity is low, due to lack of agronomic inputs.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Division Forest, Nature and Landscape Research

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