Data from: Designing networks of freshwater and marine conservation areas accounting for cross-realm connectivity and threat propagation

Integrating connectivity into systematic conservation planning is crucial
to capture ecological processes and ensure long-term conservation of
biodiversity. Although advances have been made in structural and
functional connectivity, most studies focus on single-realm or
single-species approaches. This study applied the Marxan spatial
prioritization tool to identify conservation priorities in the freshwater
and marine realms under four scenarios, each applying different approaches
to connectivity and threat propagation. Despite differences between
scenarios, all met conservation objectives, and the planning units
consistently selected between scenarios covered approximately 19% of the
freshwater realm and 12% of the marine realm, highlighting priority
conservation areas aligned with the Kunming-Montreal Global Biodiversity
Framework for 2030. The most effective approach integrated connectivity
within- and cross-realm connectivity while taking into account propagated
threats. When considering how threats from terrestrial upstream areas
spread into connected freshwater and marine ecosystems, conservation areas
were strategically placed in less threatened regions. This resulted in a
more effective spatial configuration of the reserve system. This study
highlights the importance of integrating cross-realm connectivity and
threat propagation when designing new or expanding existing networks of
conservation areas, such as the Natura 2000 European network of protected
areas. These findings emphasize the need for multirealm planning that
supports species persistence, protect transitional habitats, and accounts
for cross-realm threats.