Tetrad distributions for some selected pairs of British species
I have been wondering what I wish to learn from the BSBI Atlas 2020 project. At hectad scale I already have the New Atlas of the British and Irish Flora with its species captions. For change at tetrad scale I have BSBI’s Change in the British Flora 1987-2004, and for detailed species accounts I have my own Short Flora of Berwickshire and a range of other County Floras. These, taken together, enable me to interpret the stunning detail now available on the BSBI Distribution Database (DDb), with its facility to allow searches of individual records. It has occurred to me to experiment with the tetrad distributions of two species superimposed. I have found the exercise rewarding and present the results of my mini-project here. All the maps relate to the period 1987-2019.