"Downzoning" describes a government agency's rezoning a parcel of land once previously zoned for a more intense use to a more restrictive use (e.g., changing the commercial zoning designation of an undeveloped parcel of land to agricultural or open space). Those who purchase an undeveloped property zoned for commercial, industrial, or residential uses, only to later have that property rezoned for agricultural or open space uses unquestionably suffer a loss. But when is it compensable?