Climate connectivity priority areas in western North America

Omniscape

This page provides links to several datasets that were generated for and presented in Littlefield et al. 2017, a paper entitled "Connecting today's climates to future analogs to facilitate species movement under climate change" (full citation below). These datasets represent potential movement routes of organisms which will need to shift their range in response to climate change. Conserving the areas which hold a high number of potential movement routes can help facilitate these range shifts and thus reduce loss of biodiversity as climate changes.

Increasing connectivity is an important strategy for facilitating species range shifts and maintaining biodiversity in the face of climate change. To date, however, few studies have included future climate projections in efforts to prioritize areas for increasing connectivity. The data linked below identifies key areas likely to facilitate climate-induced species movement across western North America. Using historical climate datasets and future climate projections, the researchers mapped potential routes between current climates and their future analogs with a novel moving-window analysis based on electrical circuit theory. In addition to tracing shifting climates, the approach accounts for landscape permeability and empirically-derived species dispersal capabilities. The researchers compared connectivity maps generated with the new climate-change informed approach to maps of connectivity based solely on the degree of human modification of the landscape. The results show that including future climate projections in connectivity models substantially shifts and constrains priority areas for movement to a smaller proportion of the landscape than when climate projections are not considered. Potential movement, measured as current flow, decreases in all ecoregions when climate projections are included, particularly when dispersal is limited, making climate analogs inaccessible. The results illustrate that movement routes needed to track changing climatic conditions may differ from those that connect present-day landscapes, and that incorporating future climate projections into connectivity modeling is an important step towards facilitating successful species movement and population persistence in a changing climate.

The new connectivity analysis approach, called Omniscape, was developed based on Circuitscape, one of the most widely-used software packages for connectivity analysis. More information on Omniscape can be found here.

 Figure 3. Minimum cumulative exposure (MCE)
Figure 1. Conceptual diagram illustrating how Omniscape calculates potential movement between climate analogs in landscapes with varying degrees of human modification (darker grey regions are more natural, lighter regions are more affected by humans). (a) Analogous climates in natural areas (represented here by green squares, enlarged for illustrative purposes) are identified within a specified search radius—here, encompassing the Portland, Oregon metropolitan area on the left and the more natural area surrounding Mt. Adams in Washington State on the right. The central green square represents future climatic conditions (i.e., the target) and the surrounding green squares represent historical climatic conditions (i.e., sources). One amp of current is injected into each source, and electrical current then flows between the climate analogs (represented here by red arrows), following low-resistance paths in the human-modified landscape. (b) Using a circular moving window, this procedure is repeated across the landscape in a spatially continuous manner (here, the windows are separated for illustrative purposes). Flow is higher and more evenly distributed in the less-modified landscape (here, surrounding Mt. Adams) than in the human-dominated landscape (here, surrounding Portland, Oregon). Potential movement within each moving window (c) is summed to result in a continuous map (d) of connectivity between historical and future analogs, with low values of potential movement (measured as current flow in amps) in blue and high values in yellow.


Figure 4. Classification of velocity and minimum cumulative exposure (MCE)

Figure 2. Potential movement in Washington State (a) between climate analogs without considering human modification (i.e., a uniform resistance value of 1 was applied across the study area and there was no naturalness criteria for climate analogs); (b) across a human-modified landscape but not including climate analogs (i.e., within a given moving window, Circuitscape injects current from all natural cells—not only matching climate analogs—that may then flow to the central target cell); and (c) between climate analogs across a human-modified landscape (as per methods described in the text). The connectivity impact of climate projections (d) was computed by normalizing and then taking the difference between potential movement that does not (b) and does (c) link climate analogs: red areas in (d) are important for climate-induced movements whereas green areas emerge as important for connectivity when climate change is not considered. Sources and targets for connectivity (i.e., climate analogs) were constrained to only the most natural areas, except in (a). The color ramp of (a), (b), and (c) reflects the low (blue) and high (yellow) values of potential movement for each frame. Thus, the colors are not directly comparable across frames, and results should be interpreted with regards to relative importance of specific areas for potential movement. Analogous climates were defined for the historical time period and the 2080s using MIROC5 projections under RCP 8.5, and a dispersal rate of 0.5 km/yr was used. The channeled scablands of southeastern Washington, referenced in the text, are circled in (b).

Figure 4. Classification of velocity and minimum cumulative exposure (MCE)

Figure 3. Potential movement in two time steps versus one and for two different dispersal capacities across a human-modified landscape. (a) and (b): potential movement between climate analogs from the historic-2050s period; (c) and (d): potential movement between climate analogs from the subsequent 2050s-2080s period; and (e) and (f): potential movement between climate analogs from the historic-2080s period (i.e., one extended time step). Panels on the left reflect dispersal capacities of 0.5 km/yr, and panels on the right reflect dispersal capacities of 5 km/yr. Analogous climates were defined using MIROC5 projections under RCP 8.5. Sources and targets for connectivity (i.e., climate analogs) were constrained to only the most natural areas. The color ramp reflects the low (blue) and high (yellow) values of potential movement for each frame. Thus, the colors are not directly comparable across frames, and results should be interpreted with regards to relative importance of specific areas for potential movement. The western-most foothills of the Cascades, referenced in the text, are circled in (a).

Data

Each archive provides results relevant to one of 3 general circulation models (GCMs) that were chosen to be representative of variation within a broader group of GCMs: a) INM CM4 (Volodin et al. 2010), which projects low levels of climate change for the study area; b) MIROC5 (Watanabe et al. 2010), which projects moderate change; and c) GFDL CM3 (Donner et al. 2011), which projects considerable change. There are 4 gridded products contained in each of the 3 GCM files linked below:

a) potential movement including resistance and climate;

b) potential movement including resistance and NO climate ;

c) potential movement including NO resistance but climate;

d) connectivity impact of including climate projections (computed by standardizing and then subtracting mvmt WITH climate from mvmt with NO climate).

Relevant parameters/values used throughout (unless otherwise noted) are:

1. RCP - RCP8.5 (high emissions scenario).
2. Time period: historical (1961-1990) to "2080s" (2071-2100) analogs.
3. Dispersal rate - 0.5 km/year.
4. Resistance values were squared where included.
5. Climate analog threshold was 0.9 PCA units.

This data has been prepared for the AdaptWest project and its development was funded by the Wilburforce Foundation. All input climate datasets can be obtained from AdaptWest (https://adaptwest.databasin.org/pages/adaptwest-climatena). All archives have been compressed with the 7-zip utilty. To extract the data, use the 7-zip software, which is freely available for Windows (link) as well as Mac and Linux systems (link). Use of 7-zip in place of the standard zip format allows better compression, lower storage costs, and shorter download times.

Picture
Littlefield, C. E., McRae, B. H., Michalak, J., Lawler, J. J. and Carroll, C. (2017), Connecting today's climates to future analogs to facilitate species movement under climate change. Conservation Biology. Accepted Author Manuscript. doi:10.1111/cobi.12938

Data files
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INM-CM4
Zipfile: ASCII format
MIROC5
Zipfile: ASCII format
GFDL-CM3
Zipfile: ASCII format