When you think about weather, invasive species likely do not come to mind. You probably think about what you might need to wear or if your family outing will be under sunny skies. For those of us working on invasive species, weather makes a difference, too.
Weather helps to determine the success of plant and animal invasions. Temperature and precipitation affect growth, reproduction and mortality. It also influences the timing and effectiveness of detection and management efforts. Some years seem to be a bumper crop for invasive species growth and expansion.
While the warm, dry weather of the last two summers was ideal for fieldwork, this summer's cool, wet and windy weather was challenging. The chronic rains required adaptive scheduling of terrestrial invasive plant management because herbicide treatments should be applied only when it is dry with low wind. Poor weather also made it difficult to conduct lake surveys for aquatic invasive species, as calm, sunny weather enables easier detection of unwanted plant and animal populations below the water's surface.
The early frost further complicated management efforts. A hard frost ends the growing season for some species, and thus, the control season. Two of the most aggressive invasive plants in the region are Japanese knotweed and common reed grass. These plants also are among the most susceptible to frost. In past years, we treated infestations into October, but this year's frost hit in early September, marking the end of most management. As a result of the inconsistent weather, invasive plant managers were racing the clock to treat all of the infestations that were prioritized for control.
Average weather patterns from year to year, i.e. climate, help to determine the plant and animal species that can survive here over time. As weather becomes more unpredictable, predicting which invasive species will arrive and thrive becomes more difficult, making prevention and management more complex.
Biologists say, in general, we can expect the following invasive species challenges in a changing climate:
1. There will be altered transport and introduction mechanisms. Invasive species are introduced both intentionally and unintentionally through human activities. As climate enables greater trade and travel in new locations for longer durations of time, there will be greater opportunities for species introductions through commercial shipping and recreational activities.
2. We will see new invasives. Not all non-native species that are introduced are able to survive in their new environments; however, changing environmental conditions may enable invasive species to overcome these constraints.
3. Impacts from existing invasives may change. The abundance and competitive advantage of invasive plants and animals that are already here may increase as native species decline and resources become more available.
4. The distribution of existing invasive species may change. Species that are intolerant to cold, such as the tree-killing pest hemlock woolly adelgid, can find new homes here with warmer winters.
5. The effectiveness of control strategies may also be altered. Biological controls - the release of a host-specific predator to limit the spread of an invasive species - may be affected as species inter-relationships become imbalanced.
Invasive species are a challenge already, so how can we expect to succeed in a changing climate that throws more obstacles our way? Luckily, we are well positioned in the Adirondacks to effectively address invasive species. The region has less disturbance, which is often a precursor for invasion. The region's large, relatively intact forests and waterways also give nature an upper hand at withstanding invasion and being resilient to changes. Furthermore, programs put into place now will address invasives that are already here and also those that may be on their way.
We can improve our prevention programs to stop the arrival of invasives; ramp up monitoring programs to help detect new introductions; institute response systems to control their establishment and spread; and, coordinate efforts to bolster our ability to successfully address invasives. All of these initiatives are underway in the region and can be strengthened with your help. To get involved, contact the Adirondack Park Invasive Plant Program at 518-576-2082.
Eye on Invasives is a seasonal biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at www.adkinvasives.com.