Scientists' Contributions

Spatial Associations Between Acidification and Bird Species Distribution in Britain

D. E. Chamberlain, R. Warren, H. Q. P. Crick, Jane Hall, Sarah Metcalfe and Duncan Whyatt

    The hypothesis that anthropogenic acidification has had a detrimental effect on bird species distributions in Britain was tested by analysing two ornithological data sets in relation to Sulphur deposition and a measure of critical load exceedance (exceedance ratio). The analyses were based on the known distributions of all breeding bird species in Britain which have been measured by two Breeding Bird Atlases in 1968-72 and 1988-91 and considered frequency of occurrence and change in distribution. The main aim was to assess whether bird distributions could be used as bio-monitors of acidification abatement strategies in terrestrial ecosystems. Of nine invertebrate-feeding species selected for analysis, all showed some support for the above hypothesis. For some species, frequency of occurrence in 1988-91 was less likely in 10-km squares with greater Sulphur deposition (Redshank, Dipper) or greater exceedance value (Stonechat, Lesser Whitethroat). For others, species extinction between 1968-72 and 1988-91 was less likely (Lapwing, Redshank, Dipper, Redstart, Ring Ouzel), or species colonisation more likely (Little Ringed Plover, Lesser Whitethroat) in 10-km squares showing decreases in Sulphur deposition. These associations were significant, even when habitat variables that were also significant predictors of species distributions were included in the models [you need to say what type of models]. The number of significant models showing an apparently detrimental effect of Sulphur deposition was 10, compared with 2 apparently beneficial effects and 6 non-significant or inconclusive relationships. The corresponding numbers for exceedance ratio were 3, 8 and 7 suggesting that Sulphur deposition, per se, and not exceedance ratio appears to be more consistently detrimental with respect to bird species distribution. Forecast reductions in deposition over the next decade (the most consistent predictor) were used to predict changes in species range by 2010. Lapwing, Little Ringed Plover and Lesser Whitethroat showed the greatest predicted changes with deposition.