Invasive Plants & Animals
An estimated 209 or more invasive species have been either accidentally or intentionally introduced into the Great Lakes basin. Introduced plants, such as purple loosestrife, garlic mustard, autumn olive, common reed grass and Eurasian milfoil, and animals, such as gypsy moth, zebra mussels and round gobies, have resulted in major ecological and economic costs (Mills et al. 1994, Schloesser et al. 1998, Edsall 1998, Madenjian et al. 2002). See the Ecological Overview for more information about the kinds of invasive species in Michigan and vectors for introduction.
Displacement of indigenous populations by invasive species cause altered food webs, nutrient dynamics, natural processes and life-history patterns of the native fauna and flora. Invasive species are recognized as a significant factor in the decline of at least 46% of federally listed endangered species (Pimental et al. 1999). Many invasive plants form dense monocultures that deprive native species of space, light and nutrients, altering the structure and composition of natural communities; consequently, wildlife species are deprived of native food sources and other necessary habitat elements.
The monetary effects of invasive species are also substantial, due to property damage, loss of economically viable resources, and the cost of control and restoration efforts. Estimates place the total cost of invasive species in the United States at more than $123 billion dollars annually (Pimental et al. 1999). During the next ten years, an estimated three million dollars will be spent on monitoring and control of zebra mussels alone (Harrison 2003).
A recent assessment of invasive species policy at the national level concluded, "Existing legislation on non-indigenous species is fragmented, reductionist, and lacks comprehensive coverage and policy philosophy. Research is needed into how best to develop a policy, what it should look like, and how it could be enforced. At this point prevention of further introductions of invasive non-indigenous species is unquestionably the most prudent policy, one that could save billions of dollars in damage as well as prevent extensive perturbations to native ecosystems and endangered species" (Williams and Meffe 1998).
To address these issues, a 1999 Executive Order created the National Invasive Species Council (NISC). The NISC completed a national management plan for invasive species (NISC 2001), but invasive species continue to be a major threat.
The following examples illustrate Michigan's vulnerability to invasive species.
Once limited to the great prairies of central United States, Brown-headed cowbirds spread eastward as forests were removed and became fragmented and the land was developed for farming. In its original range, other bird species had developed behavioral defenses to the cowbird's nest parasitizing activities, but new species encountered did not have these defenses. In Michigan, cowbirds became a significant threat to the Kirtland's warbler. Prior to implementation of cowbird controls, nearly 70% of Kirtland's warbler nests contained one or more cowbird eggs, measured net reproductive rates fell to less than 40%, and in some locations, successful reproduction was completely eliminated (USFWS 1985). Cowbirds are also suspected in reducing the success of numerous other songbird species (Robinson et al. 1993).
While the Great Lakes continue to be susceptible to new introductions of exotics via international commerce through the St. Lawrence Seaway (Kolar and Lodge 2002), they are also threatened with the potential movement of four Asian carp species from the Mississippi/Illinois River System through the Chicago Ship Channel. Bighead and silver carp, which currently occur in very large numbers in the Illinois River (Koel et al. 2000, Pegg et al. 2002), grow to very large sizes and consume large volumes of zooplankton throughout their long lives. These species would have a significant effect on production of native fish throughout the Great Lakes by limiting zooplankton, a primary food source for native fish during early life stages. Black carp were recently discovered in the Illinois River (Chick et al. 2003). Introduction and proliferation of this species, which feeds on molluscs, would cause further declines in native mussel and snail populations (Strong and Pemberton 2000), and greatly reduce productivity in coastal wetlands by limiting fingernail clams, an important food source for several waterfowl species. Grass carp have increased throughout the Mississippi and Illinois rivers through natural reproduction (Raibley et al. 1995, Koel et al. 2000). They feed voraciously on vegetation and have the potential to substantially alter vegetated Great Lakes coastal areas, which are critical to fish and wildlife diversity and productivity.
Emerald Ash Borer
Although first discovered in southeast Michigan in 2002, the emerald ash borer (EAB) is believed to have been introduced to Michigan 6-10 years ago in packing crate material from eastern Asia. EAB larvae girdle trees as they feed under the bark, which has led to the destruction of millions of ash trees in Livingston, Macomb, Monroe, Oakland, Washtenaw and Wayne counties. Recent surveys have identified EAB in additional counties throughout the Lower Peninsula. An intensive management effort is underway to prevent further spread of this species within the State, because it could significantly change the forested landscape in areas where ash is a major component. Preliminary findings by the USFS estimate the potential timber value loss of ash resources across the U.S. at $20-60 billion (U.S. Department of Agriculture 2003).
Conservation Needs to Address Invasive Species Threats:
Conservation actions, research and monitoring identified here are patterned after the national management plan developed by the NISC (2001).
Land, Water & Species Management
- Develop and implement strategies to prevent new introductions of aquatic invasive species into the Great Lakes Basin by predicting the next likely invasive species threat
- Develop a statewide strategy using an Integrated Pest Management approach, to identify invasive species in Michigan, their potential to affect native landscapes and species, and opportunities for control
- Identify and develop environmentally safe biological agents which can be employed to control invasive species
- Identify, develop and implement management techniques (e.g., prescribed burning, pesticides, water control) to control or eliminate invasive species
- Develop land management practices and training to deter invasive species establishment and spread
- Prioritize and implement invasive species control actions using accepted methods
- Identify areas of significant invasive species concentrations
- Develop restoration plans for sites where invasive species have been controlled
Law & Policy
- Develop and implement invasive monitoring and inspection systems for private aquaculture, the bait industry, the ornamental fish and plant industries, the shipping industry, and recreational boaters
- Develop and implement a legal strategy that compensates the State of Michigan for natural resource damages from the introduction of invasive species
- Establish State regulations or actions that work to negate or restrict potential introduction pathways
- Provide incentives for propagation and use of native plants as the preferred alternative for landscape developments
- Develop and implement regulatory structures that assist in preventing the introduction of aquatic invasive species from bait and private aquaculture industries
- Develop, enact and enforce legislation requiring Great Lakes shipping vessels to disinfect ballast water prior to entering the Great Lakes or when loading and unloading in Great Lakes ports
- Develop and implement effective policies and regulatory structures to prevent the introduction of aquatic invasive species from the ornamental fish and plant industry and to provide for proper disposal of unwanted exotic species
- Seek regulatory changes designating aquatic invasive species as injurious organisms whose release is directly regulated under the Federal Clean Water Act
Education & Awareness
- Conduct an educational awareness campaign on invasive species in the State and prevention of their spread
- Provide landowners with information and tools to control invasive species
- Develop informational material that promotes use of native species in landscaping
- Develop an inter-State strategy to improve legislation and enforce existing policies
- Coordinate efforts between agencies, NGOs, businesses and individuals to develop a response strategy to contain and prevent establishment of newly introduced invasive species
- Encourage private landowner participation in restoration projects through professional assistance, tax incentives and project funding
Research, Surveys & Monitoring
- Develop techniques to identify potential effects of future invasive species on native species and landscapes, and opportunities for control
- Establish monitoring and protocols to detect newly introduced species and new occurrences of known invasive species
- Develop models to predict the next likely invasive species threats to help monitoring efforts
- Determine whether linear landscape features and human-created disturbance aid in range expansion of invasive species
- Develop invasive species monitoring and inspection systems for private aquaculture, the bait industry, the ornamental fish and plant industries, the shipping industry, and recreational boaters
- Conduct research on known invasive species to identify their effects on native species and landscapes, and to provide information critical to control and restoration efforts
- Conduct research and monitoring efforts to develop and test management techniques (e.g., prescribed burning, hydrologic management, pesticides) for invasive species control
- Conduct research to develop environmentally safe biological agents to control invasive species
- Conduct research to develop and test land and water management practices that will deter the establishment and spread of invasive species
- Develop science-based priorities for invasive species control
- Conduct research to provide information critical to restoration plans
- Track the abundance, distribution and initial appearance of invasive species