A tradeable development rights (TDR) program focusing on biodiversity conservation faces a crucial problem: defining which areas of habitat should be considered equivalent. Restricting the trading scope to a narrow area could boost the range of biodiversity conserved but could increase the opportunity cost of conservation. The issue is relevant to Brazil, where TDR-like policies are emerging. Long-standing laws require each rural property to maintain a legal forest reserve (reserva legal) of at least 20%, but emerging policies allow some tradeability of this obligation. This paper uses a simple, spatially explicit model to simulate a hypothetical state-level program. We find that wider trading scopes drastically reduce landholder costs of complying with this regulation and result in environmentally preferable landscapes.