Global variation in terrestrial conservation costs, conservation benefits, and unmet conservation needs

Abstract

Our ability to identify cost-efficient priorities for conserving biological diversity is limited by the scarcity of data on conservation costs, particularly at fine scales. Here we address this issue using data for 139 terrestrial programs worldwide. We find that the annual costs of effective field-based conservation vary enormously, across seven orders of magnitude, from <$0.1 to >$1,000,000 per km(2). This variation can be closely predicted from positive associations between costs per unit area and an array of indices of local development. Corresponding measures of conservation benefit are limited but show opposing global trends, being higher in less developed parts of the world. The benefit-to-cost ratio of conservation is thus far greater in less developed regions, yet these are where the shortfall in current conservation spending is most marked. Substantially increased investment in tropical conservation is therefore urgently required if opportunities for cost-effective action are not to be missed.

Figure 1

Variation in the annual management cost of conservation projects; note axes are log₁₀-transformed. (a) Annual cost km⁻² vs. wilderness value; for comparison only, the open symbols are well-respected U.K. and U.S. zoos; these are not included in any analysis. (b) Annual cost km⁻² vs. mean per capita GNP. (c) Observed vs. fitted values from the multiple regression model of annual cost given in Table 2.

Figure 2

Variation in the estimated benefits of field-based conservation projects. (a) Area that could be effectively conserved for $1,000,000 y⁻¹ vs. mean per capita GNP. (b) Mean number of threatened bird species per 1/4° grid vs. mean per capita GNP. (c) Ratio of threatened bird density to annual cost km⁻² vs. mean per capita GNP.

Figure 3

Regional variation in the percentage of the overall cost of effective reserve networks that are met. These figures refer to the estimated overall costs of expanded networks (from ref. 9), but the positive correlation with mean regional GNP holds also for the percentage of existing reserve management costs that is currently met (r_s = 0.72, n = 10, P < 0.05).