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Keywords:

  • Marxan;
  • migratory fish;
  • protected areas;
  • species distribution modelling;
  • tropics

Summary

1. Protected area networks for river ecosystems must account for the highly connected nature of river habitats and the fact that conditions in distant locations can influence downstream habitats and biota. We used Marxan conservation planning software to address the unique constraints of reserve design in river ecosystems and structure a reserve network to overcome key challenges to freshwater conservation.

2. The range limits of 63 fish species in Mesoamerica were predicted and used in Marxan to design a network of conservation focal areas that encompasses 15% of the range of each species in areas with low risk of environmental degradation. Upstream risk intensity was estimated by propagating landscape-based sources of stress downstream along the direction of flow in GIS. We constrained Marxan solutions to account for basin divides, and we defined critical management zones to include important habitats that contribute to species persistence and mitigate threats.

3. The proposed reserve network encompassed 11% of the study area, half of which was contained within existing protected areas. Our exercise also identified important gaps in protection. Because terrestrial-based environmental risks were propagated through the river network and considered in the solution, focal areas were constrained to catchments with low levels of upstream human activity. Addition of critical management zones – riparian buffers and fish migration corridors – expanded the network area by one-fifth.

4. Our application of Marxan allowed longitudinal connectivity and topographic barriers to species movement to be considered. Adding critical management zones expanded the size of the reserve network, but is crucial to the network’s conservation efficacy. We call for an evaluation of the added management capacity needed to conserve critical management zones and suggest ways to further improve the reserve design process.