Maximizing conservation benefit for grassland species with contrasting management requirements.
Abstract
Conservation management often encompasses multiple, alternative management actions on a given site, involving habitat restoration and maintenance for example. Which actions are preferable depends on the conservation goals, the expected outcomes of actions, and their associated costs. When actions affect habitat quality differently, species that vary in habitat requirements will not respond to the actions in the same way. When all these species are of conservation concern, trade-offs between them are inevitable and the selection of appropriate actions becomes less straightforward. Although this is a common planning problem, it has received little attention in the conservation planning literature. We demonstrate how to obtain cost-effective planning solutions for a set of species with contrasting requirements, when multiple alternative conservation actions are available for each site. We investigate the strength of trade-offs between species with different habitat preferences, when planning optimal management of a set of semi-natural mesic grassland sites. A community of vascular plants and Lepidoptera species depends on such grasslands, which are maintained by cattle grazing. The various species differ in their responses to grazing intensity. We apply an algorithm that selects a grazing intensity for each site to maximize the benefit over all species, under a given budget constraint. The optimal grazing intensity for sites, and consequently, the expected representation of species, was sensitive to the relative values assigned to species (weights) and the budget available. The outcome also depended on assumptions regarding species representation under suboptimal management. A sensitivity analysis showed that the trade-offs between species were strong, illustrating the potentially significant consequences of conservation decisions. Synthesis and applications. Maximizing conservation benefit over all species may result in high representation of some species at the cost of others. Although this is a natural consequence of budget limitations and conservation priorities, understanding these consequences is essential if planning is to accommodate species with different conservation needs. Our methodology is a novel extension of conventional reserve selection methods and can support planning for species with contrasting requirements, leading to more robust and cost-effective conservation decisions.