Conservation by Translocation -
Article by Dr Phil Smith MBE
the story of the Isle of Man Cabbage
The reintroduction of extinct or rare species is big news at present - take, for example the White-tailed Eagle in Scotland or the Red Kite in several areas of Britain. We might even get the Beaver back one day.
Here, on the Sefton Coast, we have our own (smaller scale) contributions with several rare plants being the subject of translocation efforts. One such is the Isle of Man Cabbage Coincya monensis monensis, a large, showy crucifer with yellow flowers and characteristic grey-green, deeply divided leaves. This is a Nationally Scarce plant that is unique to Britain and confined to western sandy coasts. The New Atlas of the British & Irish Flora (2002) records it in only 34 ten-kilometre grid squares.
The Isle of Man Cabbage has always been extremely local on the Sefton Coast. Its traditional haunt for most of the 20th Century was sand-dunes between Crosby and Blundellsands, but this population was progressively reduced by housing development until, by 1990, it was restricted to a sandy footpath 60m long, bordering a new block of flats. Then, in 1992, it was learnt that the flats' residents intended to turf over the footpath, thereby destroying the habitat. Fortunately, a rescue operation was organised by Lancashire Wildlife Trust and Sefton Ranger Service; about 385 one-year-old plants were dug up and replanted in two nearby sand-dune areas at Crosby Marine Park and Hall Road, Blundellsands. The sites were carefully chosen to provide suitable habitat for the Isle of Man Cabbage.
Two years later, in 1994, it was discovered that only 30 plants had survived - a 92.5% mortality! However, almost annual monitoring thereafter showed that the two populations increased progressively, with some fluctuations, and spread widely from the original points of introduction. By 2003, a total of 510 plants was present, 248 at Crosby Marine Park and 262 at Hall Road. Meanwhile, the areas of sand-dune occupied by plants increased from about 1000 squares metres in 1998 to 6000 square metres in 2003; a great success story!
The only other known colony of Isle of Man Cabbage on our coast is at Southport Marine Lake. When it was found in 1989, a total of 347 plants was counted, and this increased to 874 in 1997. Another small population, discovered in 1983 in the Birkdale Sandhills, has become extinct.
As the Isle of Man Cabbage is a Priority Species in the UK Biodiversity Action Plan, we have a special responsibility for its conservation. Hopefully, this attractive and unusual plant will continue to grace our shores in the foreseeable future thanks, in part, to a successful translocation exercise.