Critical list

by Anne Bell

Every year the Species at Risk in Ontario (SARO) list grows longer. In February, the Committee on the Status of Species at Risk in Ontario added four new species to the provincial list: eastern flowering dogwood, Ogden’s pondweed, eastern pondmussel and a subspecies of the red knot. While the causes of decline are complex in most cases, invasive exotic species and habitat degradation are the primary ones.

In Ontario and throughout eastern North America, the spread of an exotic fungus has caused dramatic declines in the eastern flowering dogwood. Exotic invasive species threaten Ogden’s pondweed and the eastern pondmussel. The pondmussel, once one of the more common freshwater mussels in Ontario, now remains only in Lake St. Clair and a tributary of the St. Lawrence River. Like most of our freshwater mussels, it has been decimated by the zebra mussel, a non-native invasive species that, unfortunately, is here to stay (see “The mussel crisis,” Winter 2008/09).

The rufa subspecies of the red knot, which breeds in the Canadian Arctic, has experienced a dramatic population decline of 70 percent over the past 15 years. This bird migrates an amazing 15,000 kilometres between Canada and Tierra del Fuego, at the tip of South America, every spring and fall. The bird appears to be suffering primarily from the decline of its primary food source at one of its key staging sites during migration – Delaware Bay in the United States. There, it needs to refuel on the eggs of spawning horseshoe crabs, but overharvesting, beach erosion and shoreline development have decimated the crab population.

The changes to the SARO list included a change in the status of the redside dace from threatened to endangered. The main threats to this species are habitat degradation and exotic invasive species. The siltation of streams, the clearing of streamside vegetation, and changes in water quality and quantity are taking their toll (see “A fish in the city,” Spring 2009). Urban development threatens several of the remaining populations of redside dace, yet so far their habitat has not received protection under Ontario’s new Endangered Species Act.