Data for: Forecasting shifts in habitat suitability of three marine predators suggests a rapid decline in inter-specific overlap under future climate change

Aim: To estimate spatiotemporal changes in habitat suitability and
inter-specific overlap among three marine predators: Baltic grey seals
(Halichoerus grypus grypus), harbour seals (Phoca vitulina), and harbour
porpoises (Phocoena phocoena) under contemporary and future conditions.
Location: The southwestern region of the Baltic Sea, including the Danish
Straits and the Kattegat, one of the fastest-warming semi-enclosed seas in
the world. Methods: Location data (>200 tagged individuals) were
analysed within the maximum entropy (MaxEnt) algorithm to estimate changes
in total area size and overlap of species-specific habitat suitability
between 1997-2020 and 2091-2100. A total of eleven candidate predictor
variables were considered representing anthropogenic activity,
environmental, and climate sensitive oceanographic conditions in the area.
Sea surface temperature and salinity data were taken from representative
concentration pathways [RCPs] scenarios 6.0 and 8.5 to forecast potential
climate change effects. Results: Model output suggests that habitat
suitability of Baltic grey seals will decline drastically over space and
time, largely driven by changes in sea surface salinity and a loss of
currently available haulout sites following sea level rise in the future.
A similar though weaker response was observed for harbour seals, while
suitability of habitat for harbour porpoises was predicted to remain
fairly stable over space and time. Inter-specific overlap in highly
suitable habitat was predicted to increase slightly under RCP scenario 6.0
when compared to contemporary conditions but to largely disappear under
RCP scenario 8.5. Main conclusions: Marine predators in the southwestern
Baltic Sea and adjacent waters may respond differently to future climatic
conditions, leading to divergent shifts in habitat suitability that are
likely to decrease inter-specific overlap. We, therefore, conclude that
climate change can lead to a marked redistribution of area use by marine
predators in the region, which may influence local food-web dynamics and
ecosystem functioning.