Optimal Biological Carbon Sequestration Region Considered with Water Availability in North Carolina

Forest ecosystem provides us enormous benefits including good water and air quality, mitigation of flood and drought, maintenance of biodiversity, and timber. In the context of climate change, the value of the forest has increased due to its role as a carbon sink. However, studies have shown that forests reduce water availability quite significantly. Considering this, selecting regions for forestation (reforestation or afforestation) must be carefully done. This study aims to select optimal region for forestation in North Carolina based on water availability. ‘Excess water’ is defined as ‘excess water = precipitation – (evapotranspiration + human water use)’. Regions that have enough excess water were selected using spatial maps of precipitation, evapotranspiration (ET), and human water use. Then, with the consideration of land cover, acceptable regions for forestation were finally selected. In the calculation of ‘excess water’, two types of ET were used – actual ET (AET) and potential ET (PET). AET was calculated using MODIS (MODerate Resolution Imaging Spectroradiometer). However, the AET values were low and nearly invariable in time and space when compared with AET measured with other methods. Therefore forestation area based on AET might be overestimated. Because PET represents maximum possible ET, selection of forestation regions based on PET is very conservative. Thus, determining areas suitable for forestation based on PET has a lower risk than based on AET. This study shows that North Carolina has 12% ~ 24% forestation potential. And cropland has the highest potential for forestation. This method can be applied to select forestation region in other States or nations.