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BACKGROUND: The typical mandate in conservation planning is to identify areas that represent biodiversity targets within the smallest possible area of land or sea, despite the fact that area may be a poor surrogate for the cost of many conservation actions. It is also common for priorities for conservation investment to be identified without regard to the particular conservation action that will be implemented. This demonstrates inadequate problem specification and may lead to inefficiency: the cost of alternative conservation actions can differ throughout a landscape, and may result in dissimilar conservation priorities. METHODOLOGY/PRINCIPAL FINDINGS: We investigate the importance of formulating conservation planning problems with objectives and cost data that relate to specific conservation actions. We identify priority areas in Australia for two alternative conservation actions: land acquisition and stewardship. Our analyses show that using the cost surrogate that most closely reflects the planned conservation action can cut the cost of achieving our biodiversity goals by half. We highlight spatial differences in relative priorities for land acquisition and stewardship in Australia, and provide a simple approach for determining which action should be undertaken where. CONCLUSIONS/SIGNIFICANCE: Our study shows that a poorly posed conservation problem that fails to pre-specify the planned conservation action and incorporate cost a priori can lead to expensive mistakes. We can be more efficient in achieving conservation goals by clearly specifying our conservation objective and parameterising the problem with economic data that reflects this objective.

Monitoring land change at multiple spatial scales is essential for identifying hotspots of change, and for developing and implementing policies for conserving biodiversity and habitats. In the high diversity country of Colombia, these types of analyses are difficult because there is no consistent wall-to-wall, multi-temporal dataset for land-use and land-cover change.To address this problem, we mapped annual land-use and land-cover from 2001 to 2010 in Colombia using MODIS (250 m) products coupled with reference data from high spatial resolution imagery (QuickBird) in Google Earth. We used QuickBird imagery to visually interpret percent cover of eight land cover classes used for classifier training and accuracy assessment. Based on these maps we evaluated land cover change at four spatial scales country, biome, ecoregion, and municipality. Of the 1,117 municipalities, 820 had a net gain in woody vegetation (28,092 km(2)) while 264 had a net loss (11,129 km(2)), which resulted in a net gain of 16,963 km(2) in woody vegetation at the national scale. Woody regrowth mainly occurred in areas previously classified as mixed woody/plantation rather than agriculture/herbaceous. The majority of this gain occurred in the Moist Forest biome, within the montane forest ecoregions, while the greatest loss of woody vegetation occurred in the Llanos and Apure-Villavicencio ecoregions.The unexpected forest recovery trend, particularly in the Andes, provides an opportunity to expand current protected areas and to promote habitat connectivity. Furthermore, ecoregions with intense land conversion (e.g. Northern Andean Páramo) and ecoregions under-represented in the protected area network (e.g. Llanos, Apure-Villavicencio Dry forest, and Magdalena-Urabá Moist forest ecoregions) should be considered for new protected areas.