Pathways of invasion
This week we’ve been busy gearing up our seasonal staff who are eager to be part of the invasive species crusade in the Okanagan-Similkameen region.
The concept of pathways of invasion and spread is something I emphasized during training, and it seemed a topic worth sharing with readers as well.
Pathways are broadly defined as the means by which species are transported from one location to another.
Natural pathways include wind, currents and other forms of dispersal in which a specific species has developed morphological and behavioral characteristics to take advantage of.
For example, the seeds of yellow flag iris – a species that grows along our creeks and lakeshores – are designed to float on the water surface. The seeds germinate along shorelines when water recedes.
In laboratory tests, 100 per cent of yellow iris seeds floated during their first week, and at least 95 per cent continued to float for two months.
In other buoyancy tests, 25 per cent of seeds were still floating almost a year after placement in water, and 10 per cent were still floating after 429 days, the longest time period of any of the species tested.
Manmade pathways are those pathways that are enhanced or created by human activity. These are characteristically of two types. The first type is intentional, which is the result of a deliberate action to translocate an organism. The Canadian Food Inspection Agency reported that 58 per cent of invasive plants arrived in Canada through intentional introductions from other countries as agricultural crops, landscape plants, ornamentals and plants for medicinal and research purposes.
Another example is the usually wellintentioned release of unwanted pets such as red-eared sliders or goldfish into natural areas.
These unwanted newcomers increase competition for limited resources and potentially spread disease to native species.
The second type of man-made pathway is the unintentional movement of organisms. The introduction of zebra and quagga mussels to North America via the discharge of ballast water is one such example, which has been further exacerbated by the unintended overland movement of mussels on boats and trailers across the continent.
This particular example spawned the mantra of “clean-drain-dry," which refers to the actions required to intercept this pathway by thoroughly inspecting, washing, draining and drying boats, trailers and equipment to prevent the spread of invasive mussels and other aquatic organisms from one waterbody to another.
Another example is the trade in live plants from around the world that has become a major industry in North America, with new imports now valued at more than $500 billion annually in the U.S. alone.
While the importation of live plants is intended, recent research found that almost 70 percent of the most damaging non-native forest insects and diseases currently afflicting U.S. forests arrived unintentionally as contaminants with these plants.
It’s important for all of us to understand pathways, particularly those that are manmade, so we think more carefully before we partake in certain activities. Our awareness of the implications of our actions will go a long way to reduce the further spread and establishment of invasive species.
The most effective approach to prevent the introduction and spread of new invasive species is to manage the pathways through which invasive species enter and spread on land or in our waters.
For information on invasive species go to our website: www.oasiss.ca or contact the Program Coordinator for the Okanagan-Similkameen, Lisa Scott, at 250-404-0115.