Looking west down Queen Street
At eleven yesterday morning I learned that Global television wanted to interview me, an arborist, about the late changing of the leaves, in an hour — in a helicopter. I would have suggested doing the interview on a footbridge over the Don Valley, but when Global does a nature story they go big. And yes, I recognize the irony of burning significant amounts of fossil fuel to videotape leaves that have not yet fallen because of the unseasonable weather. However, it presented the opportunity to educate a wide audience about trees in a compelling way. And I got to ride in a helicopter.
After the interview I was able to take some photos, a few of which I provide below.
So first, a quick primer on why leaves change colour in the fall. Throughout the summer, leaves are full of chlorophyll, the green chemical that through the process of photosynthesis converts the sun’s energy into sugars (remember grade 9 biology?). The sugars are stored in the roots and trunk, and then used to fuel the tree throughout the year as it grows roots, branches, leaves, and fruit. In the fall, the nights get longer, the weather gets cooler, and the tree begins to shut down. Tissue forms at the base of each leaf, causing them to eventually fall off.
Looking northwest up Glen Stuart Ravine
As the bright green chlorophyll drains from the leaves, other pigments like carotenoids (which make up the oranges and yellows and have been in the leaf all along) become visible. Anthocyanins (which provide the vibrant reds and purples) are produced in the fall when some sugars become trapped in the leaves.
The vibrancy of the colours and the time the leaves drop is dictated by temperature, available moisture, and most importantly, shorter days. This year, as a result of the long summer drought, followed by a mild fall with no frost and cool rains, trees are holding their leaves longer. They are doing so partially to take advantage of the unseasonably good growing conditions by storing extra sugars they were unable to during the summer, because of the crippling drought.
One fear is that we will now have a heavy snowfall or ice storm, which is more than likely considering it is mid-November. If leaves are still on the trees and the conditions are just right, snow and ice will stick to them, greatly increasing the weight of each limb, causing some limbs to break. The impact on the urban forest, not to mention the people and property below could be significant —all the more reason to have an ISA certified arborist routinely check the condition of trees on your property and conduct preventive maintenance if required, so they will be much less likely to suffer damage.
These photos were taken looking west from around the Scarborough Bluffs area (anyone with a keen eye for streets and landmarks please point them out). What I think is so fascinating is how clearly it demonstrates the idea of canopy cover. The deficiency with Google maps in this regard is that the photos are taken in the winter, with leaves off, so you can see the roads, but not the trees. In these photos many of the leaves are still on and are vibrant colours, making it easier to identify particular species.
Looking southwest at Glen Stuart Ravine and The Beach(es) Neighbourhood
The above photo shows a remnant patch of the red and white oak forest that would have dominated this area prior to the arrival of Europeans. Kingston Road is in the foreground. The canopy cover, or simply the area of ground covered by trees, is almost 100% in the ravine and surrounding neighbourhood. However, north of Kingston Road, the cover is much lower, likely around 15%. South of Kingston Road are the reds and oranges of the oaks, to north are the yellows of silver maples and Norway maples that were planted as street trees nearly a century ago. Off in the distance (in the top right corner) is the new, denser built, Woodbine neighbourhood.
The Hunt Club golf course and clubhouse
The above photo is of The Hunt Club golf course. The reds and browns are oaks, remnants of the pre-settlement forest. The sliver of green trees to the north of the palatial clubhouse is, I think, a grouping of remnant white pines. In the centre foreground are the bare white branches of a lone paper birch. The immaculate fairways of green grass carved into a centuries old forest are both beautiful and disturbing.
Looking west on Gerrard
The main road running up and down in the photo above is Gerrard. The darker lines to the right of it (north) are train tracks, while the large buildings in the top right corner are the apartments at Main and Danforth. To the south of Gerrard is an older neighbourhood with the yellows of maple street trees and other large trees in rear yards, elms and lindens, the occasional willow. To the north of Gerrard (in the center of the photo) is a new subdivision — note the neat rows of houses with no trees in sight. There are likely trees there, but they are still tiny. It will be decades before they grow as large as those to the south.
Looking east at a row of typical residential streets (not sure which ones, do you recognize your house?)
The canopy cover in the above photo is about 15% (Toronto’s goal is to have 35% cover). All the yard space shows that there is the opportunity for many more trees. The yellows in the front yards are likely more Norway and silver maples. What is striking is that some streets only have two or three left. At one time the entire street would have been yellow with large maples on nearly every yard; most have now died. The red colours to the south (left of the photo) are likely remnant oaks in the rear yards, spared from the axe because they were behind the houses away from the construction that took place in the front to build the houses, roads, sidewalks and utilities such as gas, electricity and water.
Looking east at the Beach(es) Nieghbourhood, bounded by Queen Street to the south (left) and Kingston Road to the north.
The canopy cover in the above residential neighbourhood is probably over 50%. This is the many mature oaks of the Beach(es) that were left standing when the area was built up in the last century. Houses were built by hand and with horses, and set in amongst the towering trees. This demonstrates the potential to grow our canopy. With some hard work and good planning all residential neighbourhoods in Toronto could be graced with a similarly beautiful protective canopy of trees.
Me looking stunned to be in a helicopter.