Distorted views of biodiversity: spatial and temporal bias in species occurrence data

Historical as well as current data on species distributions are needed to track changes in biodiversity. Species distribution data are found in a variety of sources but is likely that they include different biases towards certain time periods or places. By collating a large historical database of ~170,000 records of species in the avian order Galliformes dating back over two centuries and covering Europe and Asia, we investigate patterns of spatial and temporal bias in five sources of species distribution data; museum collections, the scientific literature, ringing records, ornithological atlases and website reports from ‘citizen scientists’. Museum data were found to provide the most comprehensive historical coverage of species’ ranges but often proved extremely time-expensive to collect. Literature records have increased in their number and coverage through time whereas ringing, atlas and website data are almost exclusively restricted to the last few decades. Geographically, our ...