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Analysis Overview As with most climate change vulnerability assessments, the ARCCVA was designed to provide information on the relative risk and, conversely, the priority needs of the region and to complement agency and Regional needs and conventions at a subwatershed scale including landscape prioritization, Shared Stewardship, and watershed prioritization under the Watershed Condition Framework. The ARCCVA analysis examined coldwater fish habitat and warmwater/riparian habitats based on three different aspects of vulnerability: exposure, sensitivity, and adaptive capacity: o Exposure – The climatic or ecological forces affecting the target ecosystems or their elements within an area of interest o Sensitivity – The known or predicted susceptibility of target ecosystems or their elements to a given level of exposure o Adaptive Capacity: The potential of target ecosystems or elements to further cope with a given level of exposure Measures of exposure were further delineated based on if the vulnerability was due to future climate or intrinsic vulnerability. Sensitivity and adaptive capacity metrics were based on intrinsic vulnerability. The ARCCVA leveraged multiple data sources to represent current and anticipated risk, involving the rescaling, analysis, and integration of 23 metrics (Figure 2) representing the base components of vulnerability (Friggens et al. 2013, Glick et al. 2011). These metrics were then combined to arrive at a vulnerability component score and ultimately a vulnerability rating. For each of the 23 metrics (Figure 2) spatial data were identified relevant to exposure, sensitivity, and adaptive capacity to represent characteristics of risk and resilience within each subwatershed. Riparian and Warmwater Habitat The majority of subwatersheds in the study area are considered riparian/warmwater systems (Figure 1). These include watersheds with perennial and intermittent/ephemeral stream segments. Because several of the metrics used in the vulnerability rating by this assessment relate to perennial waters, watersheds with perennial features inherently have more metrics/indicators influencing their vulnerability. To account for this difference between watersheds with and without perennial segments, vulnerability class ratings are classified as low, moderate, or high and perennial or non-perennial. Only those watersheds with perennial stream segments as designated in the USGS National Hydrography Dataset (NHD) are rated for the perennial metrics. The authors acknowledge that perennial springs, seeps and smaller flowing stream segments may be present in some watersheds deemed non-perennial. Where they occur, these features can have outsized ecological importance and should be considered accordingly. However, the information available at the time of this assessment precluded rating the perennial metrics for these settings. Riparian/Warmwater Climate Change Vulnerability (climate expressed) Multifactor scoring was used to determine the vulnerability rating for riparian/warmwater climate-expressed vulnerability (future climate). The metrics used in determining this rating are flow volume, flow timing, and temperature (Figure 2). Additionally, the upland CCVA rating for a given watershed influenced the rating. The climate-expressed vulnerability ratings (Table 1) for riparian/warmwater watersheds were provided for perennial watersheds only (Figure 3). For intermittent and ephemeral watersheds, the CCVA rating alone provides an overall climate vulnerability rating (low, moderate, high). Riparian/Warmwater Overall Vulnerability The overall vulnerability ratings for riparian/warmwater used a full suite of intrinsic and climate expressed metric scores (Figure 2). Overall vulnerability utilizes the combined rating for both impact (exposure + sensitivity) and adaptive capacity (Table 2). Because adaptive capacity represents the ability of the system to absorb and adjust to change, it has a compensatory effect in the overall vulnerability rating so that overall vulnerability can be expressed as exposure plus sensitivity and minus adaptive capacity. If the combined numeric score of overall vulnerability (impact minus adaptive capacity) is less than 0 then the watershed was rated as low vulnerability. These watersheds have higher adaptive capacity and are therefore considered to have lower overall vulnerability. If the combined score numeric was greater than 0 but less than 2, then the watershed was rated as moderate vulnerability. These watersheds have greater impact scores from exposure and sensitivity (impact) than adaptive capacity and therefore represent elevated climate change vulnerability. Where the combined score was greater than 2 the watershed was rated as high vulnerability. For these watersheds, the impact score was far greater than any metric for adaptive capacity to represent the highest overall climate change vulnerability relative to other watersheds. Coldwater Habitat Coldwater habitat vulnerability ratings were only developed for subwatersheds with perennial segments that have contemporary water temperatures to support coldwater species (<9o C). As a result, there are no coldwater habitat ratings for non-perennial watersheds regardless of elevation or temperature. As with riparian/warmwater ratings, only those subwatersheds with perennial stream segments as designated in the USGS National Hydrography Dataset (NHD) were rated for the perennial metrics. The authors acknowledge that perennial springs, seeps, and smaller flowing stream segments may be present in some watersheds deemed non-perennial. Where they occur, these features can have outsized ecological importance and should be considered accordingly. However, the information available at the time of this assessment precluded rating the perennial metrics for these settings. Coldwater Climate Change Vulnerability (climate expressed) Climate change vulnerability ratings for coldwater habitat were derived similar to warmwater habitat. Multifactor scoring of was used to determine the vulnerability rating for climate expressed vulnerability (Figure 4). The primary metrics used in determining this rating are flow volume and temperature (Figure 2). Additionally, the upland CCVA scoring for a given watershed influenced the rating. Similar to the warmwater counterpart, the climate expressed vulnerability ratings (Table 1) for coldwater habitat were provided for perennial watersheds only. Coldwater Overall Vulnerability The overall vulnerability ratings for coldwater habitat utilized a full suite of both intrinsic and climate-expressed metrics, with combined scores accounting for impact (exposure + sensitivity) and adaptive capacity (Table 2). Again, because adaptive capacity represents the ability of the system to absorb and adjust to change, it had a compensatory effect in the overall coldwater vulnerability rating (Figure 5). Because coldwater habitat is specific to perennial waters, overall vulnerability for coldwater systems are presented only for watersheds with perennial flow segments. A given subwatershed was rated as low if the combined intermediate scores (Figure 2) were less than 0 (sensitivity plus exposure minus adaptive capacity). These areas have higher adaptive capacity than the predicted impact and were therefore considered to have lower overall vulnerability. If the combined numeric score was greater than 0 and less than 2 then the overall watershed vulnerability was rated as moderate. Where the combined score was greater than 2, the watershed was rated as high. All Climate Change Vulnerability This rating represents comprehensive climate change vulnerability for coldwater, warmwater, and non-perennial watersheds (Figure 6). For watersheds with perennial streams, multifactor scoring was used to determine the vulnerability rating based on scoring for future stream volume and temperature (Table 1) and on CCVA ratings. For non-perennial watersheds, CCVA ratings alone were used to assign climate change vulnerability. Since the CCVA did not include the National Grasslands or desert-dominated watersheds, there will still be watersheds with no rating for ‘All Climate Change Vulnerability’. Outputs The ARCCVA resulted in an all-lands watershed-based vulnerability assessment built upon nearly two dozen indicators that represent both impact risk and adaptive capacity, and both current and climate forecast-based factors. This work helps to fulfill the Forest Service requirement for vulnerability assessment, one of the key components of the agency’s climate adaptation framework. Vulnerability assessment is essential for building an adaptation strategy, the next key component of the adaptation framework. The ARCCVA also provides a basis for related watershed assessment and for the prioritization of restoration work. Again, ARCCVA vulnerability ratings are presented for perennial and non-perennial watersheds separately. This is to distinguish the elevated ecological value of watersheds with perennial flow and to highlight uncertainty for subwatersheds where fewer metrics were used to drive overall vulnerability. Climate-expressed ratings based on late 21st-Century climate forecasts are considered conservative, according to numerical thresholds within a ruleset that was used to assign vulnerability to each subwatershed (see following Rating Key). Outputs and products for ARCCVA include this summary report, a geodatabase on SDE and the R3 GIS Library (www.fs.usda.gov/detailfull/r3/landmanagement/gis), and an interactive Storymap for viewing and customized reporting. The geodatabase forms the core of ARCCVA and can be used to construct maps to characterize areas according individual or collective vulnerability components. The Storymap provides the end user with the ability to consider each metric individually (https://storymaps.arcgis.com/stories/2d998ed0bc8743c9b6f36edc18e88ee8). Suggested citation: Wahlberg, MM, FJ Triepke, and A Rose. 2021. Riparian-aquatic climate change vulnerability assessment – Executive report. USDA Forest Service resource report available online <www.fs.usda.gov/main/r3/landmanagement/gis>. Southwestern Region, Regional Office, Albuquerque NM. 20 pp. References Friggens, M.M., K.E. Bagne, D.M. Finch, D. Falk, F.J. Triepke, and A. Lynch. 2013. Review and recommendations for climate change vulnerability assessment approaches with examples from the Southwest. USDA Forest Service Rocky Mountain Research Station Gen. Tech. Rep. RMRS-GTR-309. Fort Collins CO. 106 pp. Glick, P., B.A. Stein, and N.A. Edelson. 2011. Scanning the conservation horizon: A guide to climate change vulnerability assessment. National Wildlife Federation technical guide <www.fs.usda.gov/treesearch/pubs/37406>. Washington, DC. 168 pp. Mott Lacroix, K.E., E. Tapia, and A. Springer. 2017. Environmental flows in the desert rivers of the United States and Mexico: Synthesis of available data and gap analysis. Journal of Arid Environments 140: 67-78. Smith, D.M., and M.M. Friggens. 2017. A spatially explicit and quantitative vulnerability assessment of coldwater fish habitat and riparian corridors in the intermountain West. USDA Forest Service technical report available online <https://lccnetwork.org/sites/default/files/Aquatics%20Assessment%20SRLCC_Final.pdf>. Rocky Mountain Research Station, Fort Collins CO. 185 pp. Triepke, FJ, EH Muldavin, and MM Wahlberg. 2019. Using climate projections to assess ecosystem vulnerability at scales relevant to managers. Ecosphere,10(9), p.e02854. |