Why aren't there more green roofs in Calgary?
If you've ever tried to grow tomatoes on a balcony in Calgary, you might already know the answer to this question. It's dry, windy and cold! What doesn't dry up blows away. Anything on the building envelope is especially exposed. We face these same challenges when establishing green roofs. The manicured green roofs of Toronto and Vancouver with beautiful big trees, vines and exotic flowers unfortunately just aren't made to survive in Alberta.
That's not to say it can't be done and they can't be beautiful. It makes sense to focus on native species, which in Calgary's case is mostly grasses. Think of a native Alberta Prairie... not canola or wheat... We're talking june grass, rocky mountain fescue, alpine bluegrass and blue grama. But it's far from boring. Alberta is also home to an array of wildflowers, prickly pear cactus snowberries and more. The prairies are in fact one of the most biodiverse ecoregions on the planet
Speaking of opportunity, it's an amazing opportunity for us city dwellers to do something for one of the most endangered ecosystems in North America. Unfortunately, our native prairies are disappearing. Only about 10% of Canada’s native prairies remain intact habitat. Mixed grass prairie, what we see through most of southern Alberta, accounts for about half of all of Canada's prairies and less than 25% of the original area remains (not necessarily intact). Fescue Prairie, specific to around Calgary, is down to about 5% of its original area.
The animals that live in these areas, especially those in the fescue prairie region, are very sensitive to overgrazing and the introduction of woody species. From 1980-89 there were 25-65% declines in grassland bird species. This represents a more consistent, steeper and geographically widespread decline than any other grouping of North American species.
Native roofs aren't going to save the prairies, but they can make difference. Roofs can make up as much as 70% of the surface area in a downtown core. For plants, insects and birds, these surfaces function as islands in the uninhabitable urban environment. They can become valuable resting spots along migration paths, as well as a place for breading, nesting, hunting and foraging.
For those who spend their lives in the city, perhaps the most important thing a native roof can do is serve as a reminder and a connection to nature. The prairies are disappearing without our even knowing. It's important to know and be familiar with what Alberta looks like in its natural state.