Column: The dilemna of invasive species

A presentation on restoring wetlands in the South Okanagan left me with a notebook full of questions.

This fascinated nature apprentice has discovered there are serious challenges to successful waterway restoration. A presentation on restoring wetlands in the South Okanagan left me with a notebook full of questions.

It all began with a grey-green narrow-leafed tree. In a photo of vegetation on the meandering waterways north of Osoyoos the Russian olive is a dominant feature. The presenter pointed, “This tree is an invasive.”

The use of the word invasive felt slightly threatening as if the Russian olive might be part of a sinister plot to overthrow the South Okanagan. As the presenter continued the threat seemed to intensify. At the same time the Russian olive began to glow as a paragon of nature’s goodness. It is ideal habitat and fodder for birds, a pollen producer, nitrogen-fixer and soil restorer.

Plenty. This olive’s fondness for the riverbanks and wet areas of the South Okanagan, and amazing heat tolerance, has trumped its paragon qualities. It’s driving out the native vegetation. It’s an invasive.

The Russian olive is a tough adversary, though, and won’t go easily.

As the presenter informed us, “Besides propagating by seed, it also expands its range by suckers. But we’re determined to eradicate it. We cut it close to the ground and the exposed wound is then painted with chemical herbicide.”

Herbicide on the exposed wound? My mind reels with questions and confusion. Doesn’t this herbicide contain glyphosate, a chemical of questionable environmental safety? The tree would continue to cycle nutrients even as it dies. Wouldn’t there be some risk of this herbicide entering the water table?

Further, if birds have been attracted to this tree for its olive fruit, I suspect the seeds have already been distributed far and wide.

As it turns out, hundreds of species have been identified as invasive. Generally maligned for pushing out native species, invasives survive and thrive in the disturbed soil and habitats we’ve created and many respond with enthusiasm to rising temperatures. Climate change?

Higher temperatures and changing moisture availability puts pressure on existing or native species. At the same time we scrape away at the earth, providing the ideal setting for these hardier and more adaptable species to invade.

Wind, bird droppings and car tires carry invasives into new terrain. They arrive on animals, planes, trains, boats, shipping and us. There’s evidence that bugs, bacteria and spores can be caught up in high altitude winds that distribute their baggage from one side of the Atlantic to the other. Many species now deemed invasive have been intentionally introduced and only later has their status changed. Such is the story of the lowly dandelion.

When does a species become an invasive? When it interferes with our ability to produce food, keep our waterways free of obstructions, protect our livestock or maintain our health. Some current thinking even suggests that invasives may be the next best thing as less adaptable species are overcome. Maybe the best we can do is work to avoid unintended consequences and reduce the welcome mat we’ve provided.

Dianne Bersea is subbing for Bob Handfield who returns in August.

Views expressed here do not necessarily represent the South Okanagan Naturalists. For information of SONC meetings, speakers and events visit southokanagannature.com.

 

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