The end of the rainbow: Invasive species and the real costs of ecological monkey-wrenching
The once common and now rare rainbow clam (Villosa iris) (Photo by Karen Little, courtesy of Illinois State Museum)
Somewhere in the rivers of southern Ontario is a species few people have heard of, and even fewer have ever seen. It’s simply named the rainbow. The rainbow is a freshwater clam that gets its name from the rich iridescent colours on its shell. It’s so colourful that people once used the shells for jewelry. Like many other freshwater clams, it also has an almost unbelievable lifecycle where it recruits a fish to disperse its young by grabbing them by the head and injecting tiny baby clams into its gills. The rainbow is particularly ingenious at this, and uses a lure that looks like a delicious crayfish to attract the unsuspecting host to taxi its young to new homes. Invasive species and the real costs of ecological monkey-wrenching.
The rainbow was once widely distributed and common in many rivers and creeks in southern Ontario. Today it is extremely rare. While we did our part in obliterating the rainbow by polluting its river home, today, the number one threat to this species is invasive, non-native zebra mussels. Zebra mussels arrived in the Great Lakes region in the late 1980s in ballast water dumped from a freighter that started its journey in the Black or Caspian Sea. Within a decade, zebra mussels had spread throughout the Great Lakes and many of its tributaries, and they continue to make their way west in bait buckets and on boats. One dump of ballast water changed the fate of the rainbow along with hundreds of other native plants and animals, and the people of the Great Lakes region forever.
The story of the rainbow reflects the story of thousands of species from around the world. While habitat loss is still the number one threat to the abundance and diversity of nature, invasive species have rapidly become the second-biggest issue. In many cases, the combination of habitat loss and invasive species is proving too much for many native plants and animals (think about it like someone messing up your room, and then deciding to stay with you). Nature Conservancy of Canada (NCC) and other groups that manage land and waters for native species have needed to become vigilant for new invasive species while managing those that are established. At NCC, invasive species management is identified as a priority action on almost all nature reserves across southern Canada.
Invasive species are animals, plants and even diseases from one place that are transported to another place by people. Sometimes we do this intentionally, like bringing European starlings to North America in a celebration of the birds mentioned in the works of William Shakespeare. Other intentional introductions (or species that escaped) include the purple loosestrife, Russian olive, common carp and Norway maple. Often, the newcomers die out in this foreign land, or persist at low numbers that have almost no impact on the indigenous plants and animals. In other cases, such as zebra mussels and European starlings — freed from the diseases, predators and competitors of their homeland, non-native species can explode in numbers and come to dominate native habitats. European starlings are now one of the most abundant birds in North America, and aggressively evict other cavity-nesting birds such as eastern bluebirds, northern flickers and tree swallows.
Often introductions are unintended and species hitchhike on our goods and transports. This would include some mammals like Norway rats (which are actually from China), but invasive species are mostly composed of weedy plants and diseases. For example, no one intended to bring chestnut blight to North America in the early 1900s; it just came along with the Japanese chestnuts that were imported for a garden. Unfortunately, while the Japanese chestnuts had co-existed with chestnut blight for thousands of years and weren't seriously impacted by this disease, our North American chestnuts had no resistance and the magnificent tree that once dominated more than 80 million hectares of eastern forests was transformed to a handful of individuals.
Canada’s trees, birds and other species are not ecological weaklings. Every one of our planet’s habitats is susceptible to new species wreaking havoc when they arrive unannounced to a region’s established ecological family. Indeed we have sent our own ecological party-crashers to the corners of the Earth. Canada goldenrod is spreading rapidly across China, causing extinction of rare plants. Grey squirrels are outcompeting native red squirrels in England and yes, even our own beloved beaver is despised in Argentina and Chile, where it is threatening more than 16 million hectares of native forest. And while these species are well behaved at home, when they leave our borders they are freed of their natural regulators and become menacing, invasive species.
The good news is that we have learned many hard lessons about our ecological monkey-wrenching. We have recently come to understand the economic costs of our negligence and ill-conceived biological experiments. A recent report estimates the economic cost of invasive species to be more than $30 billion a year; a figure that surpasses the spending on healthcare in BC and Alberta. This is a combined estimate of costs to Canadian forests, lakes and agriculture. There is also a rising concern about losing the richness and uniqueness of local biodiversity to the homogeneous franchise of adaptable generalists that are spreading across Canada.
Governments are responding through better inspections of goods and transports coming into Canada. Most provinces now have coalitions that are building awareness about invasive plants. Parks and protected areas are being managed to keep new invaders out and limit the impact of the ones we have. Gardeners are increasingly demanding native plants and nurseries are no longer selling some of the worst invaders. Maybe most Canadians will never see the rainbow, eastern bluebird, American chestnut or many of our other plants and animals that are fading away under the growing pressure of invasive species. But with each piece of Canada’s nature that slips away, it seems that we are losing an opportunity. This might be an economic opportunity, an opportunity to experience healthy and intact ecosystems and opportunities for enjoyment and wonder about the richness and diversity of Canada’s plants and animals.
This post originally appeared on Science Borealis, an inclusive digital science salon featuring Canadian bloggers from a wide array of scientific disciplines.
About the Author
Dan Kraus is the director of national conservation for the Wildlife Conservation Society Canada.
