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An Expert and Community Supported Decision Tool for Managing Marine Invasive Species


Jungho Baek Jungho BaekDepartment of Economics
School of Management
Tobias Schwoerer Tobias SchwoererInstitute of Social and Economic Research
University of Alaska Anchorage


Management decisions on invasive species threatening fisheries are often ad hoc with little or no data at hand, yet timely action is the most cost-effective way to manage. This project will conduct a formal decision analysis including a risk assessment to develop a management decision tool for optimized deployment of resources to minimize the risk of invasive species on marine resources. The approach will utilize existing data, expert elicitation, a household survey, and focus groups to incorporate existing biophysical and economic data with preferences and values of experts and affected local communities. Further, we will use a bioeconomic framework to account for the long-term benefits and costs related to different management options. Finally, the analysis will seek to develop a decision tool that will inform policy decisions and risk assessments on invasive species by providing the best available scientific information, estimate economic impacts, and address community preferences and values. We will test the above methods through four case studies, one in each of the four Alaska communities affected by Elodea. Elodea is an aggressive invasive aquatic plant, non-native to Alaska, which has been found across the state in fish-bearing water bodies.

Project news can be found in the 2016 stories “Research will map risk of invasive aquatic weeds in Alaska” from Alaska Sea Grant, and “Controlling elodea with data” from the Peninsula Clarion.

In May 2017 an editorial by Tobias Schwoerer, "Aquatic invader threatens Alaska lakes, salmon, floatplane traffic", was published in Alaska Dispatch News.


The issue

Little is known about Elodea’s ability to spread and affect salmon reproduction. Recently, Elodea has been confirmed in tidally influenced waters in the Copper River Delta, suggesting that it is salt tolerant and may threaten valuable salmon fisheries. In Fairbanks it crowded out native vegetation in Chena Slough, resulting in the loss of grayling sport fishing worth several million dollars annually. In Anchorage, Elodea occurs in two lakes that are used by float planes and where property values may be affected. In Nikiski, it occurs in a lake used by sockeye salmon for spawning. Timely action is required to manage Elodea and minimize its economic and ecological harm. However, the problem is complex and little is understood about impacts to local communities, the economy, and ecosystems. Often, managers rely on their own judgment instead of being able to follow a data-driven approach that incorporates available biophysical data, expert knowledge, and the values and preferences of affected stakeholders. This problem can lead to a lack of action, poor decisions, waste of money, and conflict.

Why is this an Alaska Sea Grant project?

This project specifically addresses coastal resilience through meeting goals 1 and 5 in the Alaska Sea Grant Strategic Plan 2014–2017. The research targets improving basic understanding by Alaskans of the economic and ecological impacts invasive species can have on Alaska’s healthy marine, coastal, and watershed ecosystems. The project also helps decision–making by accounting for the values and preferences of affected communities. It provides a mechanism for eliciting and incorporating expert knowledge where data gaps exist and timely action precludes further data being collected.

Research collaborators

Alaska Department of Fish and Game
Alaska Department of Natural Resources
Alaska Sustainable Salmon Fund
Cook Inlet Aquaculture Association
Soil and Water Conservation Districts of the affected communities
US Fish and Wildlife Service


What researchers learned

The research applies Monte Carlo simulation to conduct a formal bioeconomic risk and decision analysis on Elodea, an invasive aquatic plant threatening ecosystem services in Alaska. The approach melds a metapopulation model with local market and non-market economic valuation to show that upfront management of existing invasions is the optimal strategy minimizing long-term damages. The analysis accounts for social-ecological feedback, region-specific risk, and allows for integration of species distribution models to achieve higher spatial resolution. Without intervention, damages to commercial sockeye fisheries and recreational floatplane pilots would amount to a median loss in natural capital of $1.4 billion in 2015 USD (90% CI: $0.1, $9.4 billion), providing a lower bound to potential damages. Even though the range of uncertainty is large, the certainty of long-term damages requires investments targeted at eradicating current invasions and preventing new arrivals. The study serves as a critical first step towards risk management aimed at protecting productive ecosystems of national and global significance.

Research impacts

Alaska Sea Grant demonstrates that early management of invasive aquatic elodea may prevent economic loss of $1.4 billion

Recap: Alaska Sea Grant–funded researchers developed a risk analysis tool for invasive species to estimate future costs and benefits of management action, and estimated that management of aquatic elodea in early stages of invasion may prevent economic losses of $1.4 billion over the next 100 years.

Relevance: Elodea, an aggressive, invasive aquatic plant that is non-native in Alaska, has been found statewide. It is in the Copper River Delta, suggesting it is salt tolerant and may threaten valuable salmon fisheries. The problem is complex and little is understood about impacts to communities, the economy, and ecosystems. Managers rely on judgment instead of being able to follow an approach based on data.

Response: Alaska Sea Grant–funded researchers surveyed 46 fishery management experts to determine productivity changes for Alaska’s sockeye salmon in habitats potentially invaded by elodea. They interviewed pilots of floatplanes, a major means of spreading elodea. The researchers developed a management decision tool for optimum use of resources to minimize the risk of invasive species on marine resources, to inform policy decisions and risk assessments.

Results: The risk analysis tool estimates future costs and benefits of management action and demonstrates how economic risk varies across Alaska. The tool also informs when to take action and where action should be prioritized. For elodea, results show that if no action is taken to eradicate existing invasions in Alaska, the loss of capital over a 100-year period is an estimated $1.4 billion. Researchers concluded that establishing funding mechanisms that allow early detection of elodea and rapid response is essential to prevent such a loss statewide, and determined the Bristol Bay region faces the greatest risk. They shared results with Alaska marine resource managers and published opinion pieces and interviews in media outlets statewide for the public. The tool can be applied to invasive species other than elodea.

Research outcomes

Schwoerer, T. 2017. Invasve Elodea threatens remote ecosystem services in Alaska: A spatially-explicit bioeconomic risk analysis. Ph.D. dissertation, University of Alaska Fairbanks, SGT-17-05, 192 pp. http://hdl.handle.net/11122/7639