UW Puget Sound Institute and the Washington Department of Fish & Wildlife are leading a spatially explicit risk assessment of the current and future threats to eelgrass and floating kelp habitats in Puget Sound that can be used to evaluate the distribution of burdens associated with habitat risk and inform management actions.
Email Caitlin Magel (magelcai@uw.edu) & Wendel Raymond (Wendel.Raymond@dfw.wa.gov) to learn more.
Recent declines are prompting action
Seagrass beds and kelp forests are foundational coastal habitats that exist at the marine-terrestrial interface where they are susceptible to a wide range of human impacts. It is believed that native eelgrass (Zostera marina) and floating bull kelp (Nereocystis luetkeana) are less abundant in Puget Sound compared to their historical distributions and recent, localized declines have raised additional concern. While both species are affected by natural climate variability, much of their declines are likely due to multiple anthropogenic stressors stemming from human development and climate change, including changes to nutrient and sediment loading, increasing water temperature, altered food web dynamics, and physical disturbance. Further loss of eelgrass and kelp habitats would have cascading impacts across the Puget Sound social-ecological system due to their pivotal roles in biogeochemical cycling, habitat provisioning, supporting productive food webs, and reducing currents and storm surges, among other services. In addition, both species support recreation and hold important cultural value. Therefore, conservation and restoration decisions for eelgrass and kelp should be guided by a large-scale understanding of both current and future threats to direct management interventions where they can maximize ecosystem resilience. Cumulative risk assessment is a widely used framework to identify risk from multiple threats and assist in prioritizing management actions.
Developing a cumulative risk assessment
The spatially explicit cumulative risk assessment will be conducted using an online, open source software called Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). The InVEST Habitat Risk Assessment tool combines the following information to calculate risk:
- Exposure: the spatial co-location of kelp or eelgrass habitat with each threat.
- Magnitude: an intensity category for each threat in a given pixel – either no exposure, low, moderate, or high.
- Consequence: vulnerability to a threat for:
- Eelgrass | Identified and rated via an expert panel (Thom et al. 2011)
- Kelp | Identified by an expert panel and summarized in Hollarsmith et al. (2022). Then rated by 6 experts as part of this project (see the next section for more info).
Learn more about the kelp threat rating
Kelps are susceptible to multiple environmental and biological stressors that can contribute to population decline. However, the intensity of these stressors and their ability to cause kelp population decline is not well understood. The project convened a workgroup of six regional kelp experts to rate stressors relying on their own experience, understanding of peer-reviewed literature, and general knowledge of kelp biology and ecology. Experts also rated the degree of certainty of stressor ratings in an attempt to reflect our current understanding of these stressors. This exercise was conducted for three taxa (Macrocystis, Nereocystis, and understory kelps) in two life stages – sporophyte and gametophyte.
Regional kelp experts
- Cathy Pfister, University of Chicago
- Danielle Claar, Whashington State Department of Natural Resources
- David Duggins, University of Washington
- Hilary Hayford, Puget Sound Restoration Fund
- Steve Rubin, U.S. Geological Survey
- Tom Mumford, Marine Agronomics
Spatial data gathering and synthesis of threats
The project is currently gathering and synthesizing data for the spatially explicit risk assessment. Ideally, we are looking for data sources that span Puget Sound. Check out our working document with potential data sources. Are there additional data sources you would recommend for specific stressors?
This project is funded by a Puget Sound Partnership – Scientific Research grant.