Effect of land use changes on the temporal and spatial patterns of carbon emissions and carbon footprints in the Sichuan Province of Western China,from 1990 to 2010
Land use changes significantly affect the carbon dynamics of terrestrial ecosystems,and are one of the main factors influencing climate change on a global scale. Analyzing the effects of land use on carbon emissions is important for understanding the mechanisms of carbon emissions and the success of carbon reduction and climate change mitigation efforts. In this study,we developed carbon emission,pressure index,and carbon footprint models to evaluate a carbon budget,and carried out research in the Sichuan Province of western China to estimate carbon sinks and carbon sources,based on energy consumption and land use change data from 1990 to 2010 (obtained from remote sensing technologies). The results showed that: (1) Changes in land use and energy consumption from 1990 to 2010 significantly increased carbon emissions (5407.839 * 10~4 t,or 143%),with an average annual rate of increase of 7.151% (1566.622 * 10~4 hm~2). During the same period,the carbon footprint for energy consumption increased,and the area of ecological deficit reached 1563.598 * 104 hm~2. Overall,the increase in carbon emissions was associated with a rapid increase in fossil fuel consumption as well as land use changes; (2) Land under construction (carbon source) and forests (carbon sink) were the largest carbon pools in the carbon budget. Higher carbon emissions were noted for built-up land than for other land use types. Between 1990 and 2010,there was a continuous increase in carbon sources,and a slight decrease in carbon sinks. Carbon emissions from built-up land increased by 126.27%,which was the largest percentage increase in carbon emissions; (3) There were considerable regional differences in carbon emissions and carbon footprints. The Chengdu plain,and its surroundings regions (e. g.,Chengdu,Deyang,Ziyang,and Neijiang),had higher carbon emissions,carbon footprints,and ecological deficits in 2010 than in 1990. In contrast,the west,northwest,and southwest mountainous regions and plateau areas (e. g.,the Ganzhi,Aba,and Liangshan autonomous prefectures) had lower carbon emissions in 2010 than in 1990. In general,these regions had low carbon footprints and ecological deficits because of their widespread coverage by forests and grasslands. Compared to the Chengdu plain (and its surroundings regions),these regions had relatively low fossil fuel consumption,slow urbanization rates,and limited industrial development and transportation corridors. Overall,in Sichuan,there was an increase from 1990 to 2010 in the spatial distribution and severity of carbon emissions,carbon footprints,and ecological deficits; and (4) Land use had a greater effect on carbon sources than on carbon sinks. Forests,grasslands,water areas,and unused land were the main carbon sinks,while land under construction and cultivated land were the main carbon sources. The rapid increase in carbon sources and slow decrease in carbon sinks resulted in a substantial increase in carbon emissions in Sichuan from 1990 to 2010,with the ratio of sources to sinks increasing from 4.002 in 1990 to 9.739 in 2010. In conclusion,one key focus of future carbon emission reduction efforts in Sichuan should be to maintain or increase forest areas. It would also be worthwhile to reduce carbon emissions from land under construction. Through targeted land use and land management activities,ecosystems can be managed to enhance carbon sequestration and mitigate fluxes of greenhouse gases.