Aquatic Invasive Species

Invasive species are widely recognized as negatively impacting ecological processes and economies worldwide. Significant ecological impacts include irreversible changes to ecosystem function and community composition, and loss of endangered and threatened species.  The economic impacts include extensive and increasing costs to prevent, control and eradicate invasive species populations, and resulting socioeconomic impacts to human communities. Further, the synergistic effects of climate change and invasive species play a powerful role in altering ecosystem processes. These synergistic interactions of climate change and invasive species result in intensified invasive species impacts, facilitated spread and establishment, increased susceptibility of habitats to invasion and reduced ecosystem resilience (ISAC 2023). The economic and ecological threats posed by invasive species are anticipated to increase into the future.

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Invasive species are a key driver to biodiversity loss (Gurevitch and Padilla 2004, and Maxwell et al. 2016), driving up to 60% of extinctions seen globally (IPBES 2023).  A recent synthesis of studies comparing the impacts of aquatic invasive species across multiple aquatic taxa and habitat ecosystems indicate invasive species contributed to both a decrease of abundance of species and a decrease in the diversity of aquatic communities (Gallerdo et al. 2015).

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Species-specific scenarios provide context for ecological impacts.  The ecological effects of dreissenid mussels are considered the most far-reaching relative to other aquatic invasive species, causing local extinction of many native mollusks (Strayer and Malcom 2007; Burlakova et al. 2014), changing the structure of food webs (Wainright et al. 2021) and fish assemblages (Souza et al. 2023), and contributing to the collapse of valuable fish populations (Kelly et al. 2010; Bossenbroek et al. 2009; Strayer 2009; Pimentel et al. 2005). Various invasive aquatic plants have been linked to negative changes to aquatic ecosystems once introduced to a waterbody.  For example, Myriophyllym aquaticum infestations significantly reduced dissolved oxygen concentrations in waters compared to those with native aquatic vegetation (Kuehne et al. 2016). When comparing invaded and un-invaded aquatic habitats, invasive Elodea sp. were found to have significant impacts on biofilms and nutrient cycling (McKie et al. 2023). In other ecosystems dominated by invasive milfoil, a loss of native plant species in aquatic communities was observed (Boylen et al. 1999).  The cascading effects of an aquatic invasive plant invasion can be observed in a recent example impacting wild salmonid populations. Following the introduction of Elodea spp. to Alaska waters, changes in dissolved oxygen and increased cover in Elodea-invaded habitats put salmonid fisheries at risk (Schwoerer et al. 2017). A modeling study examined suitable Elodea spp. habitat and indicated an overlap of known spawning and rearing sites for Chinook salmon and whitefish coupled with subsistence patterns of fishing in Alaska (Luizza et al. 2016). The implications of these patterns threaten the overall survival of critical fish species and the economies that they support.

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Historic economic impact assessments have indicated the damages and loss of invasive species in United States at $120 billion annually (Pimentel et al. 2005). However, more recent accounts estimate the cost of invasive species at $20–26 billion annually (Crystal-Ornelas et al. 2021, Diagne et al. 2022, Fantle-Lepczyk et al. 2022).  These assessments help describe the broad impact of invasive species across a range of taxa and economic foundations.  When examining the economic burden of aquatic invasive species at a local level, invasive species can negatively impact infrastructure (Daniels et al. 2023), create restrictions for human activity, contribute to loss of revenue (Fantle-Lepczyk et al. 2022), and reduce real estate values (Zipp et al. 2019).  

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Specific economic scenarios can be helpful to understand the scale of invasive species impacts. Invasive dreissenid mussels can affect all facility components exposed to raw water; mussels can clog pipelines and water intakes and disrupt operations at hydroelectric power plants, municipal water supply facilities, and conveyance systems used in irrigation, resulting in water lines incapable of supplying a consistent and reliable source of water (Vissichelli 2018). Invasive mussels pose serious threats to hydropower infrastructure and operations (Rumzie et al. 2021).

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Surveys have been conducted to examine the operational costs associated with dreissenid mussels at multiple hydropower facilities in the United States. The dreissenid-associated maintenance expenses for nine hydro facilities total about $464,000 annually (BOR 2021). Invasive aquatic plants pose additional impacts, such as algal blooms and degraded water quality due to excess nutrients which influence home sale price (Ara et al. 2006; Horsch and Lewis 2009; Zhang and Boyle 2010; Walsh et al. 2011; Bingham et al. 2015; Baron et al. 2016). The presence of milfoil and native aquatic vegetation in Vermont lakes decreased property value ranging from 0.3 percent to 16.4 percent depending on the degree of total macrophyte (aquatic plant) coverage (Zhang and Boyle 2010).