Land use uncertainty can trigger housing speculation. We study the federal 30-by-30 initiative, which pledged to conserve 30 percent of U.S. lands by 2030 without specifying where, when, or how. Counties with more unprotected endangered biodiversity experience higher house prices after the announcement, but only in land abundant markets, where the option value of undeveloped land is most sensitive to policy uncertainty. Vacant land values rise more sharply than house prices, investors accumulate undeveloped land, and speculation spills into housing through higher flipping and investor ownership. Prices decline after the initiative’s reversal, producing a speculative boom-bust cycle.
