Aquatic invasive species (AIS) are a major concern for our lakes and waters, yet we know surprisingly little about how they move, how to retard their movement, how to detect them early and how to eradicate them.
So, what can/should we do?
While we have very little objective knowledge about the basics of AIS, there is consensus on a number of important fronts. The list below is my assessment based on my experiences.
Very Good Consensus (More than 90% of knowledgeable people agree)
AIS are ecologically, economically and recreationally harmful. Impacts of AIS vary with species and the particular lake environments. There is little objective or quantitative information on the magnitude of these impacts, so there are often disagreements as to just how harmful AIS are.
AIS cannot be eradicated. The few cases that claim eradication are “asterisks,” meaning they are so unusual that they provide no meaningful hope or guidance. In a strict sense, many AIS could be eradicated, but only with such extreme measures they are not practical or acceptable. California has drained reservoirs for three years following invasive plant infestations and that measure has eradicated these plants.
The movement of AIS cannot be stopped. Slowed, probably. Stopped, no. The sticking point, again one where we have little quantitative or objective data, is slowed how much? There are no controlled studies and no objective baselines. So, there is a wide range of views regarding what investments of time, money and political resources should be made for what return in the level of protection.
AIS are not moved by birds, waterfowl and wildlife. For those concerned about the impacts of AIS prevention, “AIS will get there anyway,” is a common rejoinder. However, there is little evidence supporting this as a significant AIS pathway.
Good Consensus (More than 75% of knowledgeable people agree)
AIS are mainly moved by watercraft. Unfortunately, there are no definitive ways to determine the source of a newly detected AIS introduction by any pathway. Nonetheless, patterns of AIS introductions offer insights to introduction pathways, especially trailered watercraft. For example, many recent Eurasian watermilfoil introductions in Wisconsin follow major highways, suggesting trailered watercraft as a significant pathway. There are other pathways, but we do not have a good idea how important they are compared to watercraft.
Early detection/rapid response is not practically feasible. Many organizations and agencies have developed EDRR plans in response to expectations that they should do that. However, there are few (if any) case studies where this has worked. Our tools for early detection of most AIS are poorly developed and unreliable at this time. For example, zebra mussel veligers were not detected in Lake Minnetonka until a couple years after zebra mussels had already been discovered. Perhaps the most effective (at least potentially) rapid response is quarantine, but this has in most cases proven politically unacceptable. When used, it appears to be effective. For example, Lake Manitou, Indiana, was quarantined (along with aggressive herbicide treatment) following the discovery of hydrilla and so far, hydrilla is controlled (not eradicated) in Lake Manitou and no other lake in Indiana has hydrilla.
Inspections at boat ramps are effective for lowering the risk of AIS introductions. Inspections are the longest standing prevention action (after education, see below) and when prevention efforts are increased, they usually include more inspections. But, we do not have a good objective basis for answering just how inspections are effective. Evaluations of boater behavior are usually conducted by inspectors, so we do not know what boater behavior is like in the absence of inspectors. Whether the presence of inspectors alone modifies boater behavior (in a good way) or whether some other factor is at play, it appears inspections are an effective prevention method.
Education/awareness is an effective prevention tool. Education/awareness is often the first and for a long time the only prevention strategy. Once again though, we lack objective assessments. There are many studies that track changes in attitudes and self-reported behaviors, but few (if any) that evaluate actual behaviors compared to a known baseline. Education/awareness campaigns have documented positive changes in boater awareness and are appropriate to provide a foundation for additional prevention measures.
Poor Consensus (Less than 75% of knowledgeable people agree)
The significance of AIS movement by pathways other than watercraft. There are surely additional AIS pathways, but we have a poor knowledge of their significance relative to watercraft.
The movement of AIS by which particular kinds of watercraft. The most recent example is wakeboard boats, which have large water reservoirs that are difficult to decontaminate. However, much AIS movement occurred prior to the existence of wakeboard boats.
AIS should be controlled. For most AIS there are no feasible controls. For those where control tools are available, the control tools are imperfect. As well, there is little consensus regarding what are the appropriate objectives for AIS control (eradication, restoration, recreational relief?) as well as post-control assessments (does it work?).
In addition to consensus (or lack of) on these technical, physical or biological matters relating to AIS, there is substantial controversy on social, legal and “softer” matters relating to AIS. This controversy has disabled and distracted public discourse. Unfortunately, the lack of good objective information feeds into controversies and stymie’s public policy.
How can we hope to develop sound policies and practices when we lack good technical information?
That is the challenge. While most agencies’ AIS plans and goals state they intend to “stop the spread,” there is a good consensus that the absolute cessation of AIS movement is unrealistic. Further, lacking objective information on the efficacy of prevention or retardation techniques or technologies, there is a concomitant lack of a basis to say what level of AIS movement is acceptable – we will slow the spread, but how much? This is a real conundrum.
It would be useful for management agencies to set targets that reflect these realities. For example, a management objective could say there will be fewer than x new lakes infested with y species within the next z years. Setting a target provides an objective way to evaluate the efficacy of a prevention program. On the other hand, such a target risks signaling the message that it is okay for additional lakes to be infested – and few want to do that. We should not let that be an excuse. I think it is necessary to set such targets because without them, there is no objective way to evaluate prevention programs’ efficacy and then, using the actual outcomes, modifying these programs along the way.
We need more research on understanding AIS movements as well as prevention and control technologies: Much more, if we want to move beyond the current state of ignorance.
Claims of “cures,” “silver bullets,” “natural controls” and other solutions are a common occurrence when new lakes are infested with AIS. This may be more of a psychological need to do something when we lack reliable tools. Research can help, but research is necessarily systematic, methodical and time-consuming and requires substantial investments, commitments and patience. Applied research takes time.
In the face of substantial ignorance (that is, incomplete knowledge), there are two paths. The path (A) that compensates for our lack of critical knowledge regarding AIS risks provides significant overlaps and redundancies in prevention efforts. This path is most protective, but is inefficient. The path (B) that arbitrarily prioritizes (lacking knowledge means any prioritization must be arbitrary to some extent) relative AIS risks is itself risky, but this gamble is the usual “acceptable” solution because it minimizes conflict, expense and inconvenience.
Inefficiency on one hand and underestimating risks on the other. Both are bitter pills to swallow, but until we advance our scientific understanding of AIS, this is the situation. At a minimum, we should increase our research efforts and be patient for the results.
Radomski and Van Assche, in their recent book, Lakeshore Living, offered another view. They suggest that labeling AIS as “bad” is inconsistent with these species being “successful.” Ecosystems’ functions change all the time and AIS are one form of change, “Who is the judge of the merits of a changed ecosystem function?” They also argue that often our attempts to control AIS only make matters worse. To get beyond this, Radomski and Van Assche suggest that, like it or not, lake ecosystems are and will continue to be a mix of native and non-native species, so we should accept that. They recommend four goals:
Reduce human-assisted migration (of AIS).
If an invasive species poses little or no ecological or economic threat, we need not attempt to control it.
Natural resources agencies should prioritize places where they wish to re-create and maintain native coevolved diversity, then AIS should be controlled to a low abundance.
Reconciliation – described as balancing human needs with wilderness, meaning increasing diversity in domestic places and conserving species diversity in wild places. “Reconciliation recognizes that the war on invasives cannot be won …”
Radomski and Van Assche’s ideas are an interesting take and deserving of more dialog. To be operational, their ideas will require a significant shift from the status quo.
In the meantime, based on what we know, what we think we know and the AIS management system now in place, we can expect more lakes to be infested with AIS (many more with Path B compared to Path A), the rate of infestation will likely increase, that unexpected outcomes (for example Mille Lacs Lake) will occur and infested lakes will become less healthy (or resilient or less able to provide ecosystem services, etc.).
Personally, I became involved in lake ecology and management in the 1970s. At that time, lake (and many other kinds) pollution made headlines. Within a couple years of Earth Day the Clean Water Act, Clean Air Act, Endangered Species Act and the Environmental Protection Agency were established. We got our collective act together, provided real funding and got on top of these problems. To really address AIS pollution, we need to look to this case study as a model. To make progress, AIS should be addressed as a national or international problem.
AIS scare me. The nature of their impacts is more odious than other kinds of pollution – they self-replicate. AIS are a different kind of pollution. AIS are a bona fide ecological pollution, but are not recognized as pollution in a regulatory sense. We also lack basic knowledge about AIS. Simply, we lack the scientific underpinning and the institutional framework to adequately address this scourge.