http://www.inhabitat.com has a compelling story on a community of tree dwellers. As a good Canadian living in the land of forests, the potential of tree-house living is evident. The baumraum web site describes their work as:

A treehouse! A promise of adventure for the kids, a retreat for the adults, a romantic hideaway close to nature. These special little dwellings installed up among the trees fire our imagination and rouse our curiosity, bringing back childhood memories, and with them the desire to climb up and enter a magic world amongst the foliage. To be spellbound again, to witness the different sights and sounds up there by day and night and throughout the seasons. To play up there, to work undisturbed, to relax, to daydream…

It's easy to imagine communities of environmentally sustainable dwellings in private wood-lots across the province. Even the Don Valley might accommodate tree dwellings for students to study the local environment from memorable vantage points.