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.

Methods
We used the search tools on iNaturalist to download the fields that were needed for our research. We identified the county within Texas that the observation was made and then removed the original lat/long because in some cases the information was sensitive.