Assessing declines in the distributions of widespread species using community science observations

Changes in species distributions can be early indicators of decline.
Identifying species’ declines early can allow for pro-active conservation
efforts, which are more likely to be successful and be more cost-effective
than “crisis management” efforts begun after a species is endangered or
threatened with extinction. Here we investigate the changes in the
distributions of 94 widespread species in Texas to identify species
declines and patterns of decline (or expansion) across ecoregions. We
compared a large, community science dataset (iNaturalist) of observational
records with the historical record of amphibian and reptile distributions.
We also developed a method to control for observational bias in our
community science data. We found 29% of 94 widespread species exhibited
declining distributions across primarily four ecoregions, and 91.5% of
counties included in our analysis, which represent 50.8% of all Texas
counties, hosted fewer widespread amphibian and reptile species than
observed historically. The identification of distributional declines in
widespread species is important for the conservation of those taxa but can
also be an indicator of stressors affecting closely related rare or
endemic species or other species in the same ecoregion.