LETTER Diminishing return on investment for biodiversity data in conservation planning Hedley S. Grantham 1 , Atte Moilanen 2 , Kerrie A. Wilson 1,3 , Robert L. Pressey 1,4 , Tony G. Rebelo 5 , & Hugh P. Possingham 1 1 The Ecology Centre, University of Queensland, St. Lucia, Queensland 4072, Australia 2 Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65 (Biocentre III), Helsinki 00014, Finland 3 The Nature Conservancy, Australia Program Office, Suite 3.04, The 60L Green Building, 60 Leicester Street, Carlton, Melbourne, Victoria 3053, Australia 4 Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia 5 South African National Biodiversity Institute, Private Bag X101, Pretoria 0001, South Africa Keywords Biodiversity assessment; dynamic conservation planning; land-use modeling; resource allocation. Correspondence Hedley S. Grantham, The Ecology Centre, University of Queensland, St. Lucia, Queensland 4072, Australia. Tel: +61 (0) 7 3365 2527. E-mail: h.grantham@uq.edu.au Received: 15 June 2008; accepted 2 September 2008. doi: 10.1111/j.1755-263X.2008.00029.x Abstract It is generally assumed that gathering more data is a good investment for con- servation planning. However, the benefits of additional data have seldom been evaluated by analyzing the return on investment. If there are diminishing re- turns in terms of improved planning, then resources might be better directed toward other actions, depending on their relative costs and benefits. Our aim was to determine the return on investment from spending different amounts on survey data before undertaking a program of implementing new protected areas. We estimated how much protea data is obtained as a function of dollars invested in surveying. We then simulated incremental protection and loss of habitat to determine the benefit of investment in that data on the protection of proteas. We found that, after an investment of only US$100,000 (∼780,000 South Africa Rand [ZAR]), there was little increase in the effectiveness of con- servation prioritizations, despite the full data set costing at least 25 times that amount. Introduction Conservation planning is a dynamic decision-making process facilitating the implementation of management actions for conserving biodiversity (Margules & Pressey 2000; Wilson et al. 2007). Protected areas are one of the main tools for achieving conservation out- comes. Their location and management are being in- creasingly guided by conservation plans, despite a pre- vious lack of systematic assessment (Pressey 1994). Conservation plans require various forms of data in- cluding: the distribution and dynamics of biodiversity (Ferrier 2002; Drielsma & Ferrier 2006; Pressey et al. 2007); the impact and severity of threatening processes (Wilson et al. 2005); and the social, economic, political, and human circumstances that shape the context for con- servation planning (Knight et al. 2006a). Conservation planning can also consider the estimates of the poten- tial costs and benefits of different actions, and the oppor- tunities and constraints for implementing these actions (Naidoo et al. 2006; Cowling & Wilhelm-Rechmann 2007; Knight & Cowling 2007; Wilson et al. 2007). Some conservation organizations invest much time and many resources into developing effective conser- vation plans to improve decision making (Cleary 2006; Oetting et al. 2006). However, there has been little in- vestigation of the amounts and types of data that are most cost-effective in guiding conservation on the ground (Andelman & Fagan 2000; Cleary 2006; Possingham et al. 2007). Collecting more data costs time and money. If con- servation planning is to be truly efficient and effective, planners must decide if further investment in surveys, mapping, or modeling is likely to improve planning deci- sions and then weigh that expected improvement against lost opportunities while data are collected. If the return on investment from new surveys is low in terms of better 190 Conservation Letters 1 (2008) 190–198 Copyright and Photocopying: c 2008 Wiley Periodicals, Inc.