C. Kremen etal. ("aligning conservation priorities across taxa in madagascar with high-resolution planning tools," Reports, 11 April, p. 222) proposed a systematic plan for acquiring new protected areas in Madagascar, using extensive new species richness data, but their analysis did not consider the costs of acting in different regions. Costs vary substantially; omitting this important facet of conservation planning can lead to poor biodiversity outcomes. Conservation agencies are increasingly incorporating realistic costs to optimize future actions, with the help of conservation software (1,1). Analyses have shown that the including costs can considerably increase the efficiency of conservation plans, by up to a factor of 10, compared with plans that use area as a proxy (3-5). Estimated land costs in Madagascar (6) vary by up to four orders of magnitude (between USD $0.60 and $1785 per hectare), and some areas identified as priorities by Kremen et al. are in Madagascar's most expensive regions. The costs of the priority areas identified mirror the overall distribution of costs in Madagascar, whereas a more efficient solution would favor low-cost areas. Given that large areas of Madagascar have relatively low opportunity costs, much more biodiversity could have been protected with the same investment.
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