What gives you that idea? The majority of development is on 'green' land these days, as it has always been. the GTA's suburbs are growing at the fastest pace ever despite loophole filled legislation designed to curb urban sprawl. Density doesn't mean building sky-scrapers, it means using what land you already have in a more efficient manner. This would mean building in deindustrialized brown fields (the don lands), improving substandard housing (regent park)and the transportation network to deal with a more densely arranged population. Its about building mixed use neighbourhoods that are self sufficient, turning bedroom communities into fully fledged neighbourhoods. This city has so much space to rationlize outside of the downtown core as well; the inner suburbs should be where we look to increase density rather than already functionally sustainable downtown neighbourhoods.