Analysis of species distribution and range shifts is essential for understanding the effects of global environmental changes. However, the lack of well controlled survey data limits such studies in remote areas, such as the Arctic. In this study, we showed how species observations from multiple heterogeneous surveys can be analyzed jointly by assuming random variation in the survey protocols between different surveys. Our method builds on point process framework, which is a methodology that has recently received a lot of interest in species distribution modeling.
With this novel method we analyzed the 1996-2013 distributional patterns of polar bears, Atlantic walruses and ringed seals in the Kara Sea, which is one of the Arctic shelf seas. The most important covariates explaining species’ relative densities were ice concentration and distance to the coast, and regarding polar bears, also the relative density of seals. So far, spatially explicit estimates for the dependence of seals on ice concentration have been missing whereas the estimates for the dependence of polar bears on ice concentration have been mixed with the dependence on seal density. The results suggest that due to the decrease in the average ice concentration, the relative densities of polar bears and walruses slightly decreased or stayed constant, whereas seals shifted their distribution from the Eastern to the Western Kara Sea. The estimated species’ responses to environment and spatiotemporally explicit distribution predictions bring novel information for the conservation efforts in the Arctic.
Full text here: https://doi.org/10.1111/ddi.12776