The deference to local levels here is simply pragmatic. Constitutionally the environment is a provincial government responsibility. The Federal backstop is only legal because of the "peace, order, and good government" clause of our constitution.
That actually makes sense in a way. If the local government is addressing an issue the national government shouldn't need to touch it. In the US it's basically the opposite (once the federal government gets involved with something the states can't override it), and it's basically terrible because there were originally meant to be limits on what the federal government can get involved in but they've been expanded beyond all reason.
And local control can still "work" even when the same solution should apply everywhere because they can each individually adopt the same solution, the same as different countries can. In theory a province could even counteract the effect of the federal government trying to get them to spend 10% of the money by just distributing it to the population as it should have been, though of course politicians rarely have that much willpower.
