by admin » Wed Mar 25, 2020 2:59 pm
Hi Andy,
I'd forgotten what it meant. The criteria aren't sophisticated:
Based on post-1987 occurrences in a county the species must have
'Rare'
fewer than 4 distinct hectads
and fewer than 4 distinct tetrads
and fewer than 4 distinct monads
'Scarce'
fewer than 11 distinct hectads
and fewer than 11 distinct tetrads
and fewer than 11 distinct monads
Tom Humphrey
Database Officer, Botanical Society of Britain and Ireland (BSBI)
c/o Centre for Ecology and Hydrology,Maclean Building, Crowmarsh Gifford, Wallingford, Oxon, OX10 8BB, UK.
tom.humphrey@bsbi.org