Waiting can be an optimal conservation strategy, even in a crisis discipline
- aAustralian Research Council Centre of Excellence for Environmental Decisions, The University of Queensland, St Lucia, QLD 4072, Australia;
- bCentre for Biodiversity and Conservation Science, The University of Queensland, St Lucia, QLD 4072, Australia;
- cSchool of Biological Sciences, The University of Queensland, St Lucia, QLD 4072, Australia;
- dThe Nature Conservancy, Arlington, VA 22203-1606;
- eAustralian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
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Edited by Gretchen C. Daily, Stanford University, Stanford, CA, and approved August 14, 2017 (received for review February 7, 2017)

Significance
Every year, more species are driven to extinction by the combined pressures of habitat destruction, invasive species, and climate change. These ongoing losses have created a “crisis culture” in conservation, where project funds are spent as soon as they are received. We challenge this orthodoxy and demonstrate how strategic delays can improve efficiency. Waiting can allow agencies to leverage additional benefits from their funds, through investment, capacity building, or monitoring and research. With the right amount of delay, limited conservation resources can protect more species. Surprisingly, they can even do so in less time. Our results suggest that, in addition to their current focus on where to target resources, conservation managers should carefully choose when to spend these funds.
Abstract
Biodiversity conservation projects confront immediate and escalating threats with limited funding. Conservation theory suggests that the best response to the species extinction crisis is to spend money as soon as it becomes available, and this is often an explicit constraint placed on funding. We use a general dynamic model of a conservation landscape to show that this decision to “front-load” project spending can be suboptimal if a delay allows managers to use resources more strategically. Our model demonstrates the existence of temporal efficiencies in conservation management, which parallel the spatial efficiencies identified by systematic conservation planning. The optimal timing of decisions balances the rate of biodiversity decline (e.g., the relaxation of extinction debts, or the progress of climate change) against the rate at which spending appreciates in value (e.g., through interest, learning, or capacity building). We contrast the benefits of acting and waiting in two ecosystems where restoration can mitigate forest bird extinction debts: South Australia’s Mount Lofty Ranges and Paraguay’s Atlantic Forest. In both cases, conservation outcomes cannot be maximized by front-loading spending, and the optimal solution recommends substantial delays before managers undertake conservation actions. Surprisingly, these delays allow superior conservation benefits to be achieved, in less time than front-loading. Our analyses provide an intuitive and mechanistic rationale for strategic delay, which contrasts with the orthodoxy of front-loaded spending for conservation actions. Our results illustrate the conservation efficiencies that could be achieved if decision makers choose when to spend their limited resources, as opposed to just where to spend them.
- systematic conservation planning
- extinction debt
- conservation finance
- dynamic optimization
- forest restoration
Footnotes
- ↵1To whom correspondence should be addressed. Email: g.iacona{at}uq.edu.au.
Author contributions: G.D.I., H.P.P., and M.B. designed research; G.D.I. and M.B. performed research; G.D.I. and M.B. contributed new reagents/analytic tools; G.D.I. and M.B. analyzed data; and G.D.I., H.P.P., and M.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1702111114/-/DCSupplemental.
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- Biological Sciences
- Sustainability Science