Conservation priority setting in California under climate change using the network flow approach

Background/Question/Methods

Traditional approaches to conservation can be insufficient in the face of climate change and predicted shifts in species ranges.  California is particularly vulnerable because of its many endemic and threatened species.  Conservation planning under climate change faces the unique problem that areas of suitable habitat shift through time, while species are restricted in their abilities to disperse.  We modified the network flow approach (Phillips et al. 2008) to address this issue.  We demonstrate application of the tool using changes in the distribution of 2000 California native plants as the result of climate change.

The network flow approach minimizes the area needed to meet per species conservation targets while simultaneously ensuring connectivity of suitable habitat through time through explicit dispersal rules.  It is the only conservation prioritization approach we are aware of that explicitly incorporates dispersal connectivity.  Because California is large and has a large number of species, a more efficient approach  than Phillips et al. (2008) is required.

We explored the range of potential futures as well as the sensitivity of the algorithm to uncertainty in climate model used, analytical time horizon, size of conservation targets, and dispersal distance.  We also examined whether our improvements significantly changed results and conclusions.

Results/Conclusions

Network Flow analysis is possible for large domains and large sets of species.  California results are preliminary and illustrative, but illustrate several important aspects of Network Flow analysis for large domains typical of states or biogeographic analysis.  Depending on the inputs, approximately 5-10% of species are unable to meet their conservation targets through time, regardless of effort, but another 25-30% can meet their targets with some additional protection.  Furthermore, more than half of all species are able to meet their conservation targets through existing protection alone.  While the exact pixels selected for protection vary between analyses, there are focal regions that consistently contain selected pixels.  Long-term solutions are able to satisfy conservation targets for fewer species than short-term solutions, suggesting both that short-term plans may underestimate long-term conservation needs and that some connectivity chains in the short-term solutions lose their viability in the long-term.  Dispersal ability generally does not exert a large influence on solutions, except when no dispersal is assumed.