Building a database of historic land cover to detect landscape change

摘要

Since 1999, researchers at Clark University have collaborated with scientists at the Marine Biological Laboratory in Woods Hole, Massachusetts, to examine the relationship between land cover and nutrient concentrations in the Ipswich River watershed. The watershed covers 404 km~2, involves 22 towns, and drains into the Plum Island Ecosystem--Long Term Ecological Research site of the National Science Foundation. Previous research has associated increases in nitrogen concentrations with conversion from forest in 1971 to built land in 1999. Land-cover before 1971 is also important in understanding nutrient cycling; however, maps of the pre-1971 landscape exist only in paper form. The first part of this paper describes the transformation of 1951 paper maps to digital land-cover maps. The second part describes a novel technique for comparing maps from two points in time and attributing the differences to either map error or true landscape change.