Strategically timing land protection decisions to enhance biodiversity benefits.

Choices conservation organizations make when designing and implementing protected area strategies affect the timing of land protection. Well-timed habitat protection will have a greater impact on biodiversity outcomes; yet, decisions affecting the timing of protection have received much less attention than other aspects of protected area design. We reviewed evidence on the timing of protected area establishment and on temporal variation in factors influencing the ecological effectiveness and cost-effectiveness of establishing protected areas. Protected area coverage often increases in episodic bursts rather than at some uniform rate. Moreover, temporal variation in biodiversity indicators, habitat conversion threats, and the cost of protecting land suggests that the conservation benefit of protecting land at some times will be greater than that at others. Conservation organizations increase their flexibility to choose when they protect land by using flexibility-creating mechanisms, such as loans, multiyear budgeting, and endowment management. Models and theory suggest how this can be done to have the largest positive impact for conservation by exploiting long- and short-term variation in factors that affect the rate of biodiversity return on protected area investments.