Terrastory Environmental Consulting Inc.
Natural Heritage | Arborist | Environmental Policy


Reflections, ideas, and general musings at the nexus of environmental policy, natural heritage planning, and ecology in Ontario.

Why are endangered species seemingly everywhere in southern Ontario?

I get this question a lot from land development professionals in southern Ontario. Let’s face it – Endangered and Threatened species do turn up frequently during environmental studies that support development applications, which seems to contradict popular conceptions of what being “endangered” actually means. Let me try to clarify what’s going on here.

First, it's useful to reflect on what the terms “Endangered” and “Threatened” mean in a legal sense. Subsection 5(1) of the Endangered Species Act reads:

A species shall be classified as an endangered species if it lives in the wild in Ontario but is facing imminent extinction or extirpation. 

A species shall be classified as a threatened species if it lives in the wild in Ontario, is not endangered, but is likely to become endangered if steps are not taken to address factors threatening to lead to its extinction or extirpation.

So basically, an Endangered species is one facing “imminent extinction or extirpation”, and a Threatened species is “likely to become endangered” if we don’t do something about it. For some added background, “extirpation” means extinct in Ontario, but present (though potentially still at risk) elsewhere.

The first reason why some Endangered species seem ubiquitous relates to their unique traits and ecology. Some species are highly cryptic (and therefore very difficult to find during surveys) as a result of their size and/or behaviour. Many snakes are a good example of this, like the Eastern Hog-nosed Snake (Heterodon platirhinos) which occurs in low densities and moves widely across the landscape. For such cryptic species, it may not be possible to determine with sufficient certainty that the species is not present within a particular property or area - at least not without expending considerable survey time and effort (a.k.a. $). It may be simplest to just assume the species is present without knowing for sure, and protect its habitat.

The more important reason, I think, is attributable to conflation of the terms “Endangered” and “rare”. From a legal perspective (see definitions above) it is quite possible to have an Endangered species in Ontario that faces “imminent extinction” but is otherwise common. Okay, how?

Butternut (Juglans cinerea) is an instructive example. This species is legally designated Endangered in Ontario, but can be reliably found in all sorts of treed habitats (e.g., forests, open woodlands, hedgerows, fields, etc.) across southern Ontario extending onto the southernmost margin of the Canadian Shield. Butternut is Endangered because a non-native fungus known as Butternut Canker (here’s a fun scientific name - Ophiognomonia clavigignenti-juglandacearum) has decimated its population not only in Ontario but throughout its range in eastern North America. While Butternut is plentiful on the landscape, the majority are in decline, many severely, and lots are already dead. Barn Swallow (Hirundo rustica) is another one. This species is Threatened in Ontario, and while it is familiar (and sometimes abundant) in both urban and rural settings, its designation reflects steep and consistent population declines over several decades.

In short, although many Endangered species are very rare and/or localized, others aren't that hard to find. 

Something to keep in mind: as with all public policy that is informed by science, legal concepts such as “Endangered” and “Threatened” should be recognized as human constructs. They are debated and given new meaning in public settings (like parliament) outside of scientific circles. This is not to suggest that scientists and other technical experts shouldn't lead the development of criteria for establishing "endangerment" or other environmental thresholds (e.g., air quality standards, etc.) in law; of course they should. Rather, I offer that thoughtful, constructive debate between scientists, lawmakers, and the public is the most appropriate (and ultimately resilient) path to formulating good environmental policy. There is value in bridging the gap between how we define "endangered" in law and in public.

There are plenty of Butternuts (including 2 on the left) on this frequently used trail that hugs the Niagara Escarpment in Hamilton.

There are plenty of Butternuts (including 2 on the left) on this frequently used trail that hugs the Niagara Escarpment in Hamilton.

Tristan Knight