Missing the boat on freshwater ecosystem conservation in California

Background/Question/Methods

California has conserved a vast amount of public lands for natural resource protection, yet existing conservation areas have failed to protect freshwater ecosystems and their highly endemic freshwater fauna. Here, we use historic and current range maps of California’s 133 native fish species and consider (1) how an anticipatory approach to freshwater ecosystem conservation might have resulted in an alternative configuration of protected areas, (2) the extent to which current protected areas are congruent with fish conservation priority areas, and (3) dynamic ecosystem threats to priority conservation areas within and outside of the protected area network. We first generate historic and current range maps of fish species using available observation data and expert opinion.  Next, we evaluate and prioritize catchments of high potential conservation value (at the Hydrologic Unit 12-scale) using the conservation planning tool Zonation, accounting for directional river network connectivity and the fragmenting effect of dams. Finally, protected areas and freshwater ecosystem pressures (including non-native species interactions, land use, water-use pressures, and climate change) are quantified and mapped in GIS to evaluate the nature and extent of threats to freshwater fish persistence among priority areas.

Results/Conclusions

Anticipatory planning of freshwater ecosystem conservation based on historic fish distributions and unimpaired hydrologic connectivity would have resulted in the protection of large blocks of hydrologically connected catchments. There is low congruence between these historic conservation priorities and current protected area network, underscoring that areas of high freshwater biodiversity value tend to co-occur with high-value human uses (e.g., agricultural production, industrial development, etc). Most protected areas occur in high-elevation regions with few freshwater fish species and low economic value for human uses. Due to the widespread presence of dams and contraction of many species range, conservation priority areas are substantially smaller and more fragmented under current conditions compared with historic priority areas. Furthermore, high priority areas remain largely incongruent with protected areas. Non-native species interactions, land use change, flow regime alterations are all potentially important stressors in conservation priority areas, though their effects vary. The highly altered nature of California's high-priority freshwater conservation areas suggests that long-term persistence of many species will require active management of their populations in human-dominated landscapes. Because full restoration of aquatic ecosystems is not possible, we recommend a reconciliation approach in which realistic management goals are established to maintain desirable aquatic species and conditions.