Vulnerability assessments: Synthesis and application for aquatic species and their habitats in the western U.S.

The aquatics synthesis project aimed to improve access and application of relevant climate change data for resource managers based on a review and synthesis of vulnerability assessments for aquatic species and habitats across the West.

Vulnerability assessments employ a systematic method for measuring and addressing information on potential climate change impacts for a region or resource of interest (Glick et al. 2011; Friggens et al. 2013). The primary benefit of vulnerability assessments is that they supply a system to rank relative targets according to their expected response to climate related impacts and provide information pinpointing the cause of vulnerability for valued resources. Vulnerability assessments consider not only expected response of resources, but also examine the way in which a resource is affected, often in relation to other resources, to better identify management intervention points.

However, to benefit from currently available vulnerability assessments, managers must be able to access and understand information regarding their management target, which is hindered by the diversity of the current vulnerability literature. Selecting the appropriate type of assessment requires a clear understanding of how assessments are conducted and how vulnerability measures inform adaptive management actions.

This project (1) provided guidance for managers and conservationists interested in using vulnerability assessments to identify vulnerabilities and management strategies and (2) enabled better access to and interpretation of currently available data, and (3) helped effectively link vulnerability assessments with management questions and actions.

Key Findings

Researchers identified 43 vulnerability assessments and 225 impact studies that address climate change and aquatic systems in the western U.S. Some general findings from this review include:

• Targets and methods to measure vulnerability vary widely among vulnerability assessments. The place-based nature of vulnerability assessments helps tailor them to local management needs but hinders meaningful comparative analysis at larger scales.
• Aquatic vulnerability assessments tend to focus on the innate qualities of ecosystems or hydrological processes that indicate high sensitivity. Further, external non-climate stressors are often identified as the most problematic sources of vulnerability of aquatic systems and species under future conditions. In particular, over allocation (demand exceeding natural flow) and disrupted natural flows (e.g., dams) were commonly implicated issues. This focus and its apparent importance for predicting aquatic system vulnerability indicates a need for management activities that aim to reduce the impact of non-climate stressors.
• The majority of assessments consider water resources in context of the provision of services to the human sector. As a result, many aquatic assessments include considerations for both human and ecosystem vulnerability.
• Scale has an important influence on the degree to which aquatic ecosystems are considered at risk of negative impact due to climate change effects. Local-scale impacts may lead to habitat or species loss that is not captured by more generalized, large-scale assessments.
• Biophysical characteristics were most predictive of vulnerability at larger scales. Location, elevation, parent materials, and even latitude related directly to the innate sensitivity of systems to climate related changes. Biota, water quality, and exposure to stressors were more commonly used to determine the resiliency of the system to disturbances at local scales.

To learn more about this topic, see the Science Spotlight Climate change vulnerability of wildlife in Southwestern U.S. riparian habitats.

Deliverables

• Final project report that reviews and discusses the vulnerability assessment literature focused on riparian and aquatic systems in the Western U.S.
• Literature list and annotated bibliography for vulnerability assessments and climate change studies related to riparian and aquatic systems at the global, national, regional, and state levels