I would say that the biggest threat to maintaining ecological health in the park is what is happening outside of the park in terms of the greater watershed. In 2008 the David Suzuki Foundation did a comprehensive satellite analysis looking at the loss of prime agricultural land and nature from the Rouge watershed and surrounding watersheds in the GTA. We documented the loss of 11,000 hectares of green space and farmland over that period: 70% of that loss was due to urbanization, 15% of that loss was due to conversion to golf courses, and 13% was due to conversion to aggregates—pits and quarries. The impacts of tree planting were negligible.
There's no question about it: it's urbanization within the greater watershed.