From themselves, their commonwealth. It's the money they spend on the nature they use, the prices and rents paid for sites and resources. Get local government to charge some kind of land use fee. Cheap land means buyers need borrow less, shrinking mortgages. Less demand for credit also drops the lending rate.
Deflated profits makes real estate less attractive to mega-banks, more suitable to local lenders.
The property tax shift has become the cutting-edge proposal of the Sierra Club, Friends of the Earth, Sustainable America, and others. Ernest Callenbach wrote that if he had heard of site-value taxation earlier, he would have included it in his classic novel, Ecotopia. Forgoing natural values makes sustaining community tough. People moving in pushes up the cost to live there. Rising values attract speculators who further inflate site values.