Fig 1.
Projected species turnover from the early 2000s to mid-century across seven NPS geographic regions and 274 U.S. national parks.
Bray-Curtis turnover rates under RCP8.5 are calculated under the assumption that all potential extirpations and colonizations are realized, with 0 being no change and 1 being complete turnover. Circle sizes represent rates in summer, and colors represent rates in winter. Breaks in classes are based on quartiles. Alaska is shown in the inset on the left and the National Capital region is shown in the inset on the right. The chart on the right shows the mean and standard error of the mean turnover index by NPS geographic region, and the dotted lines show the mean turnover index across regions in both summer (0.23 ± SE 0.004) and winter (0.23 ± 0.006). Analysis of variance indicated significant difference among regions in summer (F(6, 267) = 13.96, p < 0.0001) and winter (F(6, 267) = 26.25, p < 0.001).
Table 1.
Change in climate suitability between the present and mid-century.
Each species within each park was classified into one of the following trends.
Fig 2.
Example of projected bird assemblage changes by mid-century at Golden Gate National Recreation Area.
Under RCP8.5 in summer, climate suitability is projected to improve for the Great Egret (Ardea alba), remain stable for the Nuttall’s Woodpecker (Picoides nuttallii), and worsen for the Wilson’s Warbler (Cardellina pusilla). Climate suitability is at risk of disappearing for the American Robin (Turdus migratorius), potentially resulting in extirpation from the park. Although the Blue Grosbeak (Passerina caerulea) is not currently found in the park, climate is projected to become suitable for this species, potentially resulting in local colonization. Bird illustrations by Kenn Kaufman.
Fig 3.
Classification of 274 U.S. national parks into trend groups based on the proportion of potential colonizations and extirpations.
Each circle represents a park. The median proportion of colonizations and extirpations across parks under RCP8.5 in summer (represented by solid vertical and horizontal lines in the plot) were used to classify parks into all trend groups except intermediate change. The upper and lower quartiles of each axis (represented by the diamond in the center of the plot) mark the boundaries of the intermediate change group. Alaska is shown in the inset on the left and the National Capital region is shown in the inset on the right.
Table 2.
Potential changes in bird assemblages by mid-century, by emissions pathway and season, as measured by (1) average ± SE of Bray-Curtis dissimilarity index across parks, average ± SE of (2) the proportion of potential extirpations and (3) potential colonizations across parks, (4) count and percent of parks with more than 25% extirpations, (5) count and percent of parks with more than 25% colonizations, and (6) count and percent of parks where the number of potential colonizations exceeds potential extirpations.
Fig 4.
Projected species composition changes from the early 2000s to mid-century across 274 U.S. national parks.
Potential (A) colonizations and (B) extirpations in summer and winter under RCP8.5 are shown as a proportion of the current total number of species. Circle sizes represent proportions in summer, and colors represent proportions in winter. Breaks in classes are based on quartiles. Alaska is shown in the inset on the left and the National Capital region is shown in the inset on the right.
Fig 5.
Relationships of the proportion of potential colonizations, extirpations, and turnover rate to latitude.
Rates/proportions between the present and mid-century under RCP8.5 in summer and winter. Significance of the regression fit is denoted by “***” where p < 0.001, and r2 values are shown next to each curve where significant.