An analysis of land cover change in Northern Virginia in the first decade of 21st century

Land cover change is a significant branch in global change researches and provides essential supporting materials for further studies on biogeochemical cycle, biodiversity, hydrology and climate changes. Based on the NLCD (National Land Cover Database), this study aims to measure the differences and spatiotemporal characteristics of land cover change from 2001 to 2011 by quantitative analysis. We designed and carried out a series of analysis experiments on NLCD for two major counties (Fairfax and Loudoun) in Northern Virginia. The results show that during the period from 2001 to 2011, the dominant land cover in Loudoun County was agricultural field, while in Fairfax County the major portion was occupied by developed land. Meantime, urban/suburban developments occurred in both counties. Developed land increasingly expanded and massively occupied agricultural land in Loudoun and forests in Fairfax. There is a significant difference in speed and scale of growth for developed land. Specifically, the area of developed land showed a continuous increase, while the area of agricultural and forest land experienced a decrease. In terms of second-level land classification hierarchy, in Loudoun County medium intensity developed land has the largest increase while the area of cultivated land has the biggest shrinking in the studied period. In Fairfax County, the barren land has the biggest change ratio with dynamic degree index of 5.22%, followed by the high intensity developed land with the dynamic degree index of 2.18% The new developed land in Loudoun County was mainly converted from cultivated land and evergreen forest land, while in Fairfax County it was mainly transferred from evergreen forest and mixed forest land. It indicates that there was a significant growth trend in speed and intensity of urban sprawl in Fairfax County. Given different location condition leads to difference of land cover pattern, the direction and scale of land cover change in both counties will greatly impact on the suitability of residential environment and public health.