The Heaths of Dorset and their Conservation

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Abstract
During the last 150 years 2/3 of the heathlands of Dorset, England, have been reclaimed for agriculture, forestry, and urban development; much of the remainder is used for military training, mineral workings and golf courses. About 6% remaining heath was grazed and about 8% burned during 1959-60. Large areas of heath are burned more than small ones and remain treeless, whereas small areas tend to become grasslands or subspontaneous pine woods according to degree of grazing pressure. Rate of destruction of Dorset heaths is increasing and only those set aside as nature reserves will survive in their present form. Distributions of 10 indicator species, Erica ciliaris and E. tetralix (Ericaceae), Ceriagrion tenellum and Pyrrhosomma nymphula (Odonata), Plebius argus and Eumenis semele (Lepidoptera) Lacerta agilis and L. vivipara (Reptilia), and Sylvia undata and Saxicola torquata (Aves) were studied to assess ability to withstand changes in land use and increased isolation in fragments of original habitat. All were able to survive slight modifications of habitat, but only lizards a total alteration of it. Increasing isolation appears to be causing an impoverishment of fauna. Scientific problems of selection and management of habitat reserves, experimental areas and spp. refuges are discussed. An example of assessing scientific value of rare species is given. Experience in running nature reserves supports concepts that an ecosystem is definable and is greater than the sum of its parts, and suggests that in any ecosystem all species are either essential (key) or nonessential. Removal of a key species radically alters the ecosystem. Stability of an ecosystem is partly a function of size; the smallest viable example of an ecosystem is that which supports a viable population of its weakest key spp.

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