Changes on the heathlands in Dorset, England, between 1987 and 1996

In 1996 all of the heathland in south-east Dorset, southern England, was su rveyed using the same recording protocols as those used in surveys in 1978 and 1987. This approach enabled the extent of the heathlands, the degree of fragmentation, and the composition of the vegetation to be compared at a l andscape scale over a period of 18 years. Between 1987 and 1996 the number of heathland patches increased from 142 to 151 and the total area of heathl and decreased by 552 ha from 7925 ha in 1987. The principal cause of this l oss is succession to scrub and woody vegetation, which continues at a rate of 1.7% per year despite conservation management. The most significant vege tation change was a decline in the area of the vegetation types, wet heath and peatland. These had remained constant between 1978 and 1987, but declin ed by 376 ha (45%) and 150 ha (25%) respectively between 1987 and 1996. Alt hough there is no direct evidence, it is speculated that changing weather p atterns or pollution might be the cause. These heaths, like many in Western Europe, are subject to a wide range of national and international legislat ive instruments designed to ensure their conservation. These measures call for the monitoring of the status of the conserved areas. This study, which has extended over almost 20 years, provides an insight in to the problems o f monitoring change in a biotope of high conservation status. (C) 2000 Else vier Science Ltd. All rights reserved.