Linking cost efficiency evaluation with population viability analysis to prioritize wetland bird conservation actions
Highlights
► We propose a two-step protocol to prioritize management actions. ► We first order the actions depending on their costs and biological benefits. ► We then compared this order with an action ranking from a population viability model. ► This process strikes a balance between rigor, complexity, practicality and information availability.
Introduction
Conserving and managing sites to protect species demands evaluation judgments because such actions often involve a choice among a set of alternatives. Competing management options might be prioritized in order to maximize species persistence. The budget for conservation is generally small relative to the number and magnitude of conservation problems and it is seldom possible to deal with all the identifiable problems. Therefore, managers have to decide how their budget can be spent most effectively (Naidoo et al., 2006, Wilson et al., 2006, Polasky, 2008).
An increasing number of researchers attempt to quantify the possible gains in conservation efficiency by including information about economic costs of locations in reserve selection (e.g., Polasky et al., 2001, Williams et al., 2003, Juutinen et al., 2004, Strange et al., 2006). These studies emphasize the value of incorporating biodiversity benefits such as increased habitat area or increased species abundance, and costs in an integrated approach with the aim of giving priority to the most cost-efficient options and, therefore maximizing net expected benefits of conservation investments. Cost-efficiency analysis are based on different approaches such as the design of reserve networks (Jantke and Schneider, 2010), the prioritization of species for conservation (Marsh et al., 2006) or the selection of management actions (Rodonini and Boitani, 2007). However, the bulk of the literature around systematic conservation planning focuses on the situation involving binary investment or zoning choices (e.g. reserve/non-reserve, restore/not-restore). Simple and workable strategies for maximizing the net benefits (in biological terms) obtained from multiple competing management actions across multiple environmental values (e.g. species, vegetation types, wilderness values) are in the early stages of development (e.g. Polasky et al., 2008, Joseph et al., 2009). Both Polasky et al. (2008) and Joseph et al. (2009) provide a compelling case for utilizing cost-efficiency in conservation planning. However, in the case of Polasky et al. (2008) the economic modeling approach utilized is challenging to implement without modeling skills that are not necessarily accessible to all practitioners (e.g. Polasky et al., 2008). In the case of Joseph et al. (2009) the subjective estimates of biodiversity benefit (expert opinion about extinction probabilities) are not transparent, and if applied in most circumstances would not make the most of available data and ecological modeling tools.
Here we attempt to strike a balance between ecological realism and practicality, by presenting a cost-efficiency action prioritization case study that exploits a simple cost-efficiency definition combined with available ecological data and models. Our approach utilizes available time-series data on species responses to habitat change and seasonal variation to underpin estimates of the biodiversity benefits arising from proposed management actions. Biodiversity benefit in this case study is measured in terms of increases to focal population abundances resulting from proposed management actions. We illustrate our approach by prioritizing non-spatial habitat restoration options for the extensive, species-rich complex of wetlands in south-eastern Spain. Our approach is twofold. First we implement a cost-efficiency analysis to identify the habitat restoration and management investments that bring the greatest expected net benefit (in terms of increased abundance of 25 waterbird species) for our fixed budget. We then attempt to evaluate our prioritization strategy by comparing the prioritized ranking of actions determined by the cost-efficiency analysis across all species with a more detailed analysis of the consequences of management options based on population viability analysis (sensu Akçakaya, 2000, Wintle et al., 2005a, Bekessy et al., 2009) for a subset of well-studied species. Combining population viability analysis (based on metapopulation modeling) with cost-efficiency prioritization approaches is novel in conservation planning (Newbold and Siikamaki, 2009, Wakamiya and Roy, 2009). Our protocol can be seen broadly as a prioritization based on cost-efficiency analysis across the full range of species of interest, followed by a quality control step that evaluates the likely outcomes for a subset of the species using population viability analysis. While the approach does not guarantee optimality in an economic sense, we believe that it is an appropriate trade-off between the practicality of simple cost-efficiency analysis (sensu Joseph et al., 2009) and the elegance and rigor of population risk assessment that cannot be practically applied to all of the species of interest.
Our specific aims were to (i) describe a management action prioritization approach in which the biodiversity benefits of candidate actions are measured using commonly available ecological data and models, (ii) illustrate how population viability analysis modeling can be integrated with a cost-efficiency prioritization scheme, and (iii) produce a cost-efficiency prioritized ranking of possible actions for managing threatened wetland bird populations in Spain.
Section snippets
Case-study: waterbirds in a wetland network
The study was conducted in the Vega Baja Valley in Southeast Spain (Fig. 1). It covers an area of 95,840 ha with a landscape dominated by citrus fruit trees, vegetables, palm trees and housing developments. In the 1980s, an inter-river water transfer was built to bring water for irrigation purposes. Since then, more than 2600 ponds have been constructed to store the water received, and the area has turned into a mosaic of crop fields and artificial wetlands (Sánchez-Zapata et al., 2005).
Apart
Action ranking
Our protocol provided information at species level about the effect of the implementation of each management action. The cost of the actions was very variable, but the range of potential effects was also high (Table 1). Some actions produced small increases in the populations and affected few species (e.g. 15 new pairs and one species for the construction of floating islands) while others had widespread effects (e.g. 846 pairs and 20 species for the installation of floating devices at the
Prioritization protocol
The analysis of management actions’ effectiveness can be an important tool in planning conservation strategies. However, a rigorous evaluation of the outcomes of the cost-efficiency analysis is necessary to ensure that the result is not simply an artifact of particular settings and assumptions made during the analysis. Several factors affected the final prioritized rank order obtained using our approach. Variation in the estimated likelihood of success and the weights assigned to species
Conclusions
Developing a method for prioritizing management options that is, both ecologically and economically, rigorous and practical to implement is a major challenge. The appropriate trade-off between rigor and practicality depends on the availability of time and expertise for the problem at hand. Many management agencies may not have the expertise and time to implement the most rigorous and sophisticated methods. Our protocol retains the elegant simplicity of existing cost-efficiency analysis, while
Acknowledgements
We want to thank the researchers and students at the School of Botany (University of Melbourne) for many interesting comments. M. Bode and T. Regan helped with the PVA. S. Gilard helped with the preparation of the maps for the PVA. The following people, organizations and natural parks provided important information and comments: M. Ferrández, G. Ballesteros, J. Sánchez, J.L. Echevarrias, S. Polo, ANSE, A. Bonet, J. Jiménez, P.M. Mújica, the Conselleria de Medio Ambiente, Agua, Urbanismo y
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