by Malgosia Halliop
A subset of our LUNA group met at Toronto Botanical Garden on May 11 for a guided tour of the ravine, hoping to soak up some of the natural and human history of the ravine as background for the sketching tours we are planning for this summer (stay tuned!). The TBG building and grounds were packed once again, with a multi-day spring plant sale in progress, the official Toronto Ravines Day celebrations on tap, and sunny spring weather luring in numerous visitors. Our guide was Peter Heinz, a volunteer tour leader at TBG, and an expert in all matters related to Wilket Creek.
Peter led us on a fascinating tour of the ravine, starting way back 20,000 years ago, when the area was covered in glacial ice. We moved forward in time through the massive melting of ice sheets almost 8,000 years later, which formed the huge glacial lake now called Lake Iroquois; the gradual carving out of ravines and changing waterways by the force of flowing rivers; and finally the waves of human inhabitants who interacted with the landscape and made their own deep changes. As we walked down into Wilket Creek ravine, Peter talked about the huge impact on the area caused by the arrival of European settlers, with all of the cutting of trees and re-routing of waterways that resulted, as well as the tragic human and cultural consequences to the indigenous people who were here first.
As we walked, we moved on to talking about the native species still thriving in the ravine as well as the encroachment of invasive species - garlic mustard, dog-strangling vine, phragmites, Norway maple - less omnipresent here than in other ravines in Toronto, but starting to creep in. The invasive plants, of course, are all native to somewhere, and in their original ecosystems would have had natural predators to keep them in check. Here, they are plants or creatures with no natural enemies - ie. they aren't eaten by anything - and also seem to have mechanisms built in that maximize their reproduction or growth and thus displace slower-growing native species. We talked about the huge challenge of managing or removing the invasives without harming the rest of the ecosystem or setting in place new chains of risky ecological consequences.
Wilket Creek ravine, however, is among the healthiest in Toronto. Among the many native plants we spotted, we revisited the marsh marigolds and skunk cabbages of our visit two weeks earlier, the marsh marigold now in abundant yellow flower all through the wetland areas, and the skunk cabbage with its large green leaves unfurled in a sculptural way (perfect for drawing after the tour was done!). We also spotted a small patch of trilliums in bloom. Peter took us to a spot on a large new bridge where we heard the banjo-twanging sound of Northern green frogs. Jan - with sharp eyes - spotted at least six individual frogs among the cattails, watercress, and other wetland plants. Peter also pointed out all the willow and dogwood that had been planted along the creek to hold the banks against erosion.
All along our route, Peter pointed out the many ways that the creek had been sculpted and rerouted by humans over the centuries, and the ongoing project to shape the creek to deal with erosion and also work around massive water and sewer pipes deep underground. This tour, more than any of my other encounters with Toronto ravines over the years, made me think hard about the challenges of meeting all the needs of the human infrastructure of the city - especially for uncontaminated drinking water and safe waste removal - while at the same time supporting the complex ecosystems in these valleys to survive and thrive.
As we looked around at all the new spring growth, we were startled to spot a huge red-tailed hawk down on the ground nearby. It seemed to be shaking something in its beak. As we all stared at it, it flew up into a nearby tree - perhaps to avoid the attention - leaving no trace of anything on the ground that we could find. While we walked further into the ravine with Peter, and then back out, the hawk treated us to a display like none of us had seen before, flying low overhead multiple times, landing on trees close around us, lifting way up into the sky to soar, and then dropping back down again. At one point, towards the end of the walk, the hawk return to perch on a tall dead tree, repeating a loud and unfamiliar call again and again. We were mystified, until Carol spotted a second hawk soaring above. We had so many questions about what we were seeing! But, in particular, this one: was this a territorial display, or mating behaviour? After some research, I'm inclined to believe the latter, and I am grateful to have been witness to part of this ritual on this beautiful spring day.