Climate Networks among Wildlife Refuges
We identified five climate categories in the refuge network and ranked them from most- to least-at-risk for climate-change impacts: 1)Disappearing climates - refuges whose current climate conditions are not represented in any other refuges in the future; 2)Isolating climates - refuges whose current climate conditions appear in only one other refuge; 3) Dispersing climates - refuges whose current climate conditions appear in multiple other refuges in the future; 4) Enduring climates - refuges that retain their current climate conditions in the future; and 5) Climate hubs - refuges that meet the current climate conditions of other refuges in the future. See Table S3 in Supporting Information for the climate categories of each refuge under each climate scenario for three future periods, 2010-2039, 2040-2069, and 2070-2099.
Disappearing climates - The current climates of six of the smaller refuges are not found in any other refuges currently (Blue Ridge NWR, Seal Beach NWR, Coachella Valley NWR, Humboldt Bay NWR, Klamath Marsh NWR, and Sonny Bono Salton Sea NWR; Fig. 2 and Table S2). By end-of-century, there is no climatically isolated refuge in all four climate scenarios, but eight are climatically isolated under three climate scenarios (Fig. 3 and Table S2). They are Antioch Dunes NWR, Marin Islands NWR, Seal Beach NWR, Sutter NWR, Colusa NWR, Upper Klamath NWR, Klamath Marsh NWR, and Sonny Bono Salton Sea NWR. These represent the units that are most climatically at risk.
However, far more refuges are at this highest level of risk when each future climate is considered separately. Under the warmer and wetter future, CNRM-CM5 RCP4.5 scenario, the current climate space of 21 refuges are not found in any refuges by end-of-century (Fig. 3a). Among these 21 refuges, 10 contain arriving current climates of other units but the other 11 do not have any connections, which means the current climate conditions of these refuges did not appear elsewhere, nor did the current climate of other refuges appear in these refuges. Under the CNRM-CM5 RCP8.5, the current climate space of 32 refuges cannot be found in any others (Fig. 3b). Among these 32 refuges, 25 do not have any climate connections. Under the hotter and drier GCM, MIROC ESM RCP4.5 scenario, the current climate space of 25 refuges cannot be found in any others and 10 refuges do not have any connections (Fig. 3c). Under the MIROC ESM RCP8.5, the current climate space of 31 refuges cannot be found in any others and 20 do not have any connections (Fig. 3d).
Isolating climates - The current climate conditions of many refuges appear in only one other unit by end-of-century (Fig. 3 and Table S2), especially those of Don Edwards San Francisco Bay NWR and Pixley NWR, which appear in only a single refuge under three climate scenarios. Under the CNRM-CM5 RCP4.5 and RCP8.5, the current climate conditions of 14 and 10 refuges can be found in only one other refuge, respectively (Fig. 3a and 3b). Under the MIROC ESM RCP4.5 and RCP8.5, the current climate conditions of 16 and eight refuges can be found in only one other unit, respectively (Fig. 3c and Fig. 3d).
Dispersing climates - For refuges whose current climates appear in many other refuges, the climate space of three refuges, Desert NWR, North Central Valley WMA, and San Diego NWR, appear in many refuges in all four climate change scenarios (Fig. 3 and Table S2). Under the CNRM-CM5 RCP4.5, the current climate conditions of the Desert NWR and of the San Diego NWR can be found 15 and eight refuges, respectively (Fig. 3a). Under the CNRM-CM5 RCP8.5, the current climate conditions of the Desert NWR and of the North Central Valley WMA can be found in eight and five refuges, respectively (Fig. 3b). Under the MIROC ESM RCP4.5, the current climate conditions of the Desert NWR and of the San Diego NWR can be found in 24 and 13 refuges, respectively (Fig. 3c). Under the MIROC ESM RCP8.5, the current climate conditions of the Desert NWR and of the North Central Valley WMA can be found in 14 and four refuges, respectively (Fig. 3d).
Enduring climates - Taking all four climate change scenario outcomes into account three refuges, San Diego NWR, Desert NWR, and North Central Valley WMA, retain their current climate conditions by end-of-century (Fig. 3 and Table S2). Under the CNRM-CM5 RCP4.5, seven refuges (Blue Ridge NWR, Bear Valley NWR, Bitter Creek NWR, Ruby Lake NWR, San Diego NWR, Desert NWR, and North Central Valley WMA) retain their current climate conditions. Under the CNRM-CM5 RCP8.5, four refuges (Hopper Mountain NWR, San Diego NWR, Desert NWR, and North Central Valley WMA) retain their current climate conditions. Under the MIROC ESM RCP4.5 and RCP8.5, four refuges (Bitter Creek NWR, San Diego NWR, Desert NWR, and North Central Valley WMA) retain their current climate conditions.
Climate hubs - The North Central Valley WMA meets the current climate conditions of 23 other refuges and its current climate space can also currently be found in 23 other refuges, the highest number of current climate connections (Figure 2 and Table S2). Next, the Desert NWR meets the current climate conditions of 17 other refuges and its current climate space can currently be found in 24 other refuges. By the end-of-century, under the CNRM-CM5, the current climate conditions of many refuges are present in Bitter Creek NWR under both emission scenarios (Fig. 3a and 3b). The current climate conditions of many refuges can be found in North Central Valley WMA under both emission scenarios of the MIROC ESM (Fig. 3c and 3d). On the other hand, using the RCP4.5 scenario, the current climate conditions of many refuges can be present in Hopper Mountain NWR and San Diego NWR using the both GCMs (Fig. 3a and 3c), while the current climate conditions of many refuges can be found in Desert NWR in both of GCMs under the RCP8.5 emission scenario (Fig. 3b and 3d).
When we see the climate network outcomes using each climate scenario separately, the current climate conditions of six refuges exist in the Desert NWR including itself and of nine refuges can be found in San Diego NWR including itself under the CNRM-CM5 RCP4.5 (Fig. 3a). The current climate conditions of seven refuges can be found in Hopper Mountain NWR and Bitter Creek NWR, respectively. Under the CNRM-CM5 RCP8.5, the current climate conditions of 11 refuges exist in the Desert NWR including itself and of three refuges can be found in North Central Valley WMA including itself (Fig. 3b). The current climate conditions of six refuges can be found in Bitter Creek NWR. Under the MIROC ESM RCP4.5, the current climate conditions of four, five, 12 refuges exist in the Desert NWR, San Diego NWR, North Central Valley WMA including itself, respectively (Fig. 3c). And, the current climate conditions of seven refuges can be found in Hopper Mountain NWR. Under the MIROC ESM RCP8.5, the current climate conditions of eight refuges exist in the Desert NWR including itself and of six refuges can be found in North Central Valley WMA including itself (Fig. 3d). The current climate conditions of six refuges can be found in Blue Ridge NWR.