Recent upperward migration of plants and animals along altitudinal gradients and poleward movement of animal range boundaries have been confirmed by many studies. This phenomenon is considered to be part of the fingerprint of recent climate change on the biosphere. Here I examine whether poleward movement is occurring in the vascular plants of Great Britain. The ranges of plants were determined from detection/non-detection data in two periods, 1978 to 1994 and 1995 to 2011. From these, the centre of mass of the population was calculated and the magnitude and direction of range shifts were determined from movements of the centre of mass. A small, but significant, northward movement could be detected in plants with expanding ranges, but not among declining species. Species from warmer ranges were not more likely to be moving northward, nor was dispersal syndrome a predictor of migration success. It is concluded that simply looking at northward movement of species is not an effective way to identify the effect of climate change on plant migration and that other anthropogenic changes obscure the effect of climate.
Keywords: Anthropogenic; Centre of mass; Dispersal; England; Halophytes; Migration; Occupancy; Range shift; Scotland; Wales.