The use of sequential vegetation maps for monitoring in coastal areas

A method is presented and discussed that minimises uncertainties in change analysis of sequential vegetation maps due tot subjectivity in boundary interpretation. This previous boundary method is based upon the concept of ‘map changes’, which implies that sequential maps are not made independently but are based upon a previous map: only changes in the old maps boundaries (both in space and vegetation typology) are interpreted. It was shown that the map changes concept increased the reliability of change analysis results in a coastal salt marsh in the Netherlands. The method may be applied easily in other studies in which photo-interpretation is used for monitoring purposes. The method is especially recommended in low dynamic areas, where slow changes in vegetation patterns take place and the effects of photo-interpretation uncertainty are relatively high.