Similarly, in lakes, infestation by invasive aquatic plants typically leads to expanding areas of dense plant growth that displace native plants, impair recreation, and can lead to a downward spiral of impacts that reduce the ecological and recreational quality of a lake.
Given these similarities, it shouldn’t be surprising that the strategies we use for controlling invasive aquatic plants are pretty similar to those that we use to treat cancer.
Cancer screening is touted as the best way to find new cancerous growth before it has spread. If not caught early, treatment options are often limited, treatment must be more aggressive, and the chances for success are lower. Similarly, in lakes, the chances for controlling new infestations of invasive plants are best when new introductions are caught early. Once a new infestation has established in a lake, it is nearly impossible to eradicate.
When cancer is caught early, doctors often opt to surgically remove the growth to prevent spread. Similarly, in lakes, new infestations of invasive aquatic plants may be removed from small areas by using hand-pulling or very localized “spot” herbicide treatments. The success of such “surgical” plant removal strategies have the greatest chance for success when used on new infestations that have been detected shortly after the initial introduction to the lake. During this early stage of a new infestation, more aggressive plant removal strategies (like cutting and harvesting) can actually speed the spread of invasive plants by creating fragments that drift to new areas and begin to grow. Consequently, harvesting and cutting should only be used in lakes with established infestations.
When treating cancer that may have spread throughout a patient’s body, localized removal is not feasible. In such cases, doctors use aggressive drugs that are designed to attack the fast-growing cancer cells while leaving healthy cells untouched. Although this sounds like an ideal strategy, these powerful drugs often impact healthy cells to some degree, leading to side-effects like hair-loss and fatigue. The best chemotherapy drugs are those that are better at targeting the bad cancer cells while being gentler on good cells.
Similarly, using herbicides to control invasive plants over large areas in lakes sounds like a perfect strategy; kill the bad plants, keep the good plants. However, herbicides almost always lead to some negative impacts on native plants. Just as some minor chemotherapy side-effects can be tolerated by patients (hair loss and fatigue), minor impacts to native plants can be tolerated in lakes. However, overly aggressive or inappropriate use of herbicides can severely damage the native plants in a lake – potentially leading to a downward spiral of negative effects on water quality and fish. Herbicides are powerful tools that must be used carefully; more herbicide does not necessarily mean better results.
When it becomes clear that cancer treatments are not working, doctors may move their focus from curing the disease to easing the suffering of the patient. In lakes with well-established infestations, it is nearly impossible to eradicate invasive plants given the tools we currently have. In such cases, managers should consider shifting their focus from getting rid of the bad plants to controlling areas where the invasive plants are causing the greatest nuisance. In such situations, carefully planned harvesting and herbicide application can help maintain acceptable recreational or ecological quality in the lake.
A Cancer Staging Model for Lakes?
Over the last few years, I have been thinking more and more about how to develop a system similar to “cancer staging” for infested lakes. We have all heard of doctors diagnosing things like “stage II lung cancer”, but what does that mean? Current cancer staging (Stage I, II, etc.) uses a combination of characteristics (form of cancer, tumor size, tumor location, patient age, etc.) to classify specific cancer situations, thus making it easier for doctors to review the treatment of similar cases. This greatly simplifies the doctor’s treatment decisions, maximizes the chances for a successful recovery, and helps to set realistic expectations.
In contrast to the current state of cancer staging and treatment, aquatic plant management strategies are usually judged by whether they have worked in a fairly small number lakes. Too often, the results are not very clear – sometimes a strategy that worked well in one lake failed miserably in another lake. Obviously, this suggests that different lakes behave differently, but how does this help us plan a treatment in our lake? “Staging” of lake infestations would help clarify which past cases were most similar to our lake, thus simplifying our management decisions, maximizing our chances for successful control, and helping to set realistic expectations.
Infestation Staging would need to incorporate such things as:
• Which invasive species has invaded
• Degree of establishment (bed size/extent/turions)
• Native plant community
• Water clarity/nutrients
• Mean lake depth & % littoral
• Sediment characteristics
I would love to talk about collaborating with others on developing this idea further. Please contact me if you have any interest.
–James A. Johnson, MS