Rahel and Olden, 2008
Assessing the Effects of Climate Change on Aquatic Invasive Species
Authors: Frank J. Rahel and Julian D. Olden
Affiliations:
Department of Zoology and Physiology, University of Wyoming
School of Aquatic and Fishery Sciences, University of Washington
Contact emails: frahel@uwyo.edu
Abstract
Climate change encompasses various components such as rising water temperatures, altered streamflow patterns, reduced ice cover duration, increased salinization, and higher demand for water management structures. These shifts substantially impact the dynamics of aquatic invasive species, due to altered pathways of introduction, establishment chances of new species, and the ecological impacts of existing invaders. The interaction between climate change and invasive species necessitates reinvented prevention and management strategies to either control moderate impacts or confront species with previously limited distributions due to seasonal temperature constraints. Findings suggest that while some invasive species might thrive in warmer conditions, many cold-water species will struggle to survive, prompting complex ecosystem responses to novel environmental stressors.
Keywords
Aquatic systems, Climate change, Global warming, Invasive species
Introduction
Climate change and invasive species are critical drivers of global environmental change, leading to potential alterations in aquatic ecosystems through temperature increases, modified streamflow patterns, and increased incidence of storms. Main motivations for aquatic invasive species spreading include human actions such as stocking, aquarium releases, and shipping activities.
Interaction Between Climate Change and Invasive Species
Predictions indicate that warmer conditions (particularly in northern regions) will have diverse impacts on species distributions and ecosystem productivity. Similar to the way climate change causes a rise in water values, warming may create opportunities for non-native species to thrive, resulting in negative effects on native biota through competition and predation.
Effects of Altered Thermal Regimes
Warmer Water Temperatures
Aquatic organisms are ectothermic; increased temperatures impact their physiology and behavior. As air temps rise, water temperatures will follow suit, altering the habitats for various species.
Pathways for Species Introductions
The climate warming leads to the expansion of suitable environments for warmwater fish culture and aquaculture practices, pushing these activities northward. For instance, for every 1 °C increase in mean air temperature, optimal catfish aquaculture zones are expected to move approximately 240 km north in the southeastern United States. As outdoor temperature raises, more tropical fish species will be kept outdoors, enhancing the chance of invasive escapes.
Over time, lakes managed for aquatic life without winter sporting constraints may increasingly facilitate invasive entries.
Likelihood of Establishment and Expansion of Non-Native Species
As climates change, native cold-water species are filtered out due to rising temperatures, reducing their establishment opportunity and allowing warm-water species to invade previously colder regions, via predictions of range expansions detailing where warmwater fishes might proliferate, including the common carp and smallmouth bass as projected by several studies.
Mediation of the Impact of Non-Native Species
Altered thermal regimes lead to shifts in dominance among species. In competitive scenarios, coldwater species, such as brook trout, which thrive in cooler environments will lose out to warmwater species like brown trout as thermal conditions improve.
In predator-prey dynamics, higher temperatures facilitate increased consumption rates by non-native predators, such as smallmouth bass and walleye, resulting in heightened vulnerability and decreased native prey fish populations.
Examples demonstrate that with a rise of 1 °C in river temperatures, per capita consumption of salmonids by smallmouth bass surges by 4-6%.
Changes in Control Strategies
Modifications Required for Management
Control strategies need adjustments in water temperatures that promote earlier growth and spread of non-native species, including the construction of barriers to block range expansions of certain invasive species. New strategies may require managing the habitats of tropical species which have historically been closely tied to more benign thermal conditions but which may now rise with climate change.
Effects of Reduced Ice Cover
Introduction and Establishment Pathways
The reduction of ice cover will promote the growth of aquatic plants, reduce winter hypoxic conditions, and increase predation risk. Winter hypoxia has historically filtered out certain predatory species; thus, its reduction can lead to biodiversity loss, replacing smaller non-piscivorous fishes with larger, predator fish. As such, increased predation by new entrants may extirpate native lower-trophic species.
Challenge of Protection and Control
Management strategies surrounding non-native invasives may need adaptation in response to altered light regime and biomass productivity due to declining ice durations, plus the need to protect native fish and amphibian populations from predation by newly emerging piscivorous fish.
Effects of Altered Streamflow Regimes
Hydrology Changes
Climate forecasts predict altered precipitation patterns, leading to increased droughts and intensified rainfall events, fundamentally modifying aquatic structure and ecological function.
Prolonged low flows may support non-native species, to the detriment of more sensitive native species, particularly when drought years correspond with pollinator species wheres patterns of flooding and drought influenced ecological community shifts in historical and ongoing studies.
Interactions and Control Strategies
Changing patterns necessitate reassessment of policies aimed at managing this new ecological complexity.
Effects of Increased Salinity
Pathways of Introductions
With climate change, increased salinity in some estuaries alters species gatherings and represents an opportunity for non-native saline-tolerant species to proliferate, impacting local native species.
Examples of Establishment Likelihoods
Salinity increases can drive both competition and establishment of new invaders due to their expected superior salinity tolerance profiles compared to native species, including plant species' competitive relationships being affected by raised salinity levels.
Control Strategies and Initiation
Future control tactics will need to consider salinity trends amidst changing hydrological conditions.
Effects of Increased Water Development Activities
As surface water diminishes, reservoir creations are anticipated as a response to climate adjustments, which could reach to enhancing pathways for other species to travel across ecosystems, while also raising the likelihood of new introductions related to human activities surrounding those water bodies.
Reservoir Impacts
Reservoir management will therefore need unique controls, given their risk of introducing non-native species through recreational avenues, with widely ranging impacts on local biodiversity, intensifying the length of infested areas.
Conclusions
The effects of climate change on invasive species hint at the increasing likelihood of non-native species filling niches left vacant by climate shifts amongst native flora and fauna.
This transition mandates a reconsideration of target species for prevention and management strategies as changing environmental conditions foster new introductions and non-native species proliferation across aquatic ecosystems, further complicating the predicaments of managing such invasions effectively and sustainably.