The Value of Chalk Grassland
Porton Down was purchased by the MOD in 1916. Sheep grazing was abandoned
and rabbits became the major grazers on the shallow, nutrient-poor soils.
During the 1950s and 60s myxomatosis in rabbits resulted in a severe
decline in grazing.
During and after both World Wars much of the chalk grassland in Britain
was ploughed. Porton Down is the largest continuous unimproved tract
remaining. The Value of the Chalk Grassland.
Soil conditions and grazing result in an abundant mixture of herbs
and grasses which supports an equally diverse range of insects.
The lack of grazing allowed incursion by more vigorous plants such
as coarser types of grass and eventually scrub came to predominate in
some areas.
Its continued existence is of national importance and 1519 hectares
of its 2750 hectares have been designated a Site of Special Scientific
Interest (SSSI).
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