Sunday, June 7, 2009

Urban Tree Conservation

On Tuesday, the City of Ottawa's Planning and Environment Committee (agenda) will be considering an Urban Tree Conservation Strategy, including the implementation of a by-law to protect distinctive (i.e. large) trees on private property within the urban boundary of the city.

We sometimes take our trees for granted in the city. The City's arborists have been pretty good at preserving our trees when they can, such as these wonderful ones in Minto Park:

Especially with the Emerald Ash Borer bug coming to take away our Ash trees, the City has been planting lots of trees, and wants to minimize the unnecesary removal of other types of trees. After all, it takes decades (or centuries) for trees to grow, yet they can come down in just minutes.

Here's one that was delivered to be installed in the median on MacLaren at O'Connor:

To really get to appreciate the amount of tree cover we enjoy in this city, though, you have to go up.

Here are some trees, mostly on NCC property from the Garden of the Provinces, to Victoria Island, across to downtown Hull:

But again that is all on public property. The proposed by-law affects trees on private property.

Even though the trees are on private property, once they've grown to a certain size and height, their removal affects the whole neighbourhood. For example, a couple of years ago, the owner of the vacant lot at Bell and Christie, just a couple of blocks South and West of Somerset/Bronson, cut down all the trees in the lot. These trees had provided shade and privacy to those in the rear-facing windows of the residence next door. This by-law probably wouldn't have saved those trees, as I doubt they were thicker than 70cm in diameter, but this situation could happen with much larger mature trees all over the city.

Have a look at Centretown. Looking South-East from Gloucester and Percy, the tree canopy carpets the entire neighbourhood until the Opus and YMCA-YWCA on the left (the only buildings in this view taller than the tree canopy anywhere in Centretown), all the way down to Lansdowne Park's Lady Aberdeen Pavillion and Civic Centre toward the right. (As always, click the photo to see it bigger)

In the foreground, you can see a high-density lowrise condo, and another one a couple of blocks behind it on the left, a lesson that high-density infill development can be attained without highrises and without breaking the below-the-treeline character of much of Centretown.

As we zoom in toward Lansdowne Park, it's evident that the whole city is covered in trees, as far as the eye can see, right up until the high-voltage power lines along the south end of the City. This tree canopy benefits the entire urban area, even if we don't always notice it from the ground.

Another view from above (though not from as high) of Dalhousie neighbourhood again shows the skyline sprinkled with trees. (Incidentally, it also shows that the tall seniors' residence built in the '60s is the only building in that neighbourhood taller than the treeline--a seven-storey building, like the one proposed by Fanto recently, would be quite out of character)

The draft Urban Tree Conservation By-Law has some noble goals, as described in the report (my emphasis):
The proposed by-law supports the conservation of trees in the urban area and will have an overall positive impact on Ottawa’s air quality, water quality, energy use, stormwater retention capacities, and climate change mitigation....

The by-law also protects large, mature trees on small lots because when trees reach maturity and their canopies are the largest, they are able to produce their greatest environmental benefits. The larger the tree, the greater its capacity to sequester and store carbon and particulate matter from the air. In new developments in Ottawa, the planting of large trees is restricted in areas containing marine clay soil, which emphasizes the importance of preserving existing mature trees.

The implementation of the by-law is particularly timely because of the discovery of Emerald Ash Borer in Ottawa. It is estimated that 25 per cent of the trees in Ottawa are ash and the pest could eliminate them within the next 10 to 15 years. Loss of these trees will have an impact on the tree canopy of Ottawa, unless steps are taken to plant new trees and conserve existing trees through the proposed by-law and other measures.

The By-Law is being considered by the Planning & Environment Committee on Tuesday, and will rise to Council on June 24th.

No comments:

Post a Comment