Identifying spatial priorities for protecting ecosystem services [v1; ref status: Indexed, http://f1000r.es/T0yHOY]

Priorities for protecting ecosystem services must be identified to ensure future human well-being. Approaches to broad-scale spatial prioritization of ecosystem services are becoming increasingly popular and are a vital precursor to identifying locations where further detailed analyses of the management of ecosystem services is required (e.g., examining trade-offs among management actions). Prioritization approaches often examine the spatial congruence between priorities for protecting ecosystem services and priorities for protecting biodiversity; therefore, the spatial prioritization method used is crucial because it will influence the alignment of service protection and conservation goals. While spatial prioritization of ecosystem services and prioritization for conservation share similarities, such as the need to document threats and costs, the former differs substantially from the latter owing to the requirement to measure the following components: supply of services; availability of human-derived alternatives to service provision; capacity to meet beneficiary demand; and site dependency in and scale of service delivery. We review studies that identify broad-scale spatial priorities for managing ecosystem services and demonstrate that researchers have used different approaches and included various measures for identifying priorities, and most studies do not consider all of the components listed above. We describe a conceptual framework for integrating each of these components into spatial prioritization of ecosystem services and illustrate our approach using a worked example for water provision. A fuller characterization of the biophysical and social context for ecosystem services that we call for should improve future prioritization and the identification of locations where ecosystem-service management is especially important or cost effective. Introduction Ecosystem services (ES) are vital for human well-being1. Much attention has been devoted to mapping and quantifying ES to achieve the dual goals of protecting biodiversity and human well-being. A growing number of broad-scale mapping studies aim to identify priority regions for conducting more localised place-based management of ES [e.g.,2–5]. Place-based management requires intensive collection of detailed socio-economic and biophysical data, and close collaboration with stakeholders for effective decision making6,7. Given limited resources and information, and increasing threats to ecosystems, it is not possible to do these comprehensive analyses everywhere in a timely manner. We argue that there is currently an under-appreciated, but vital role for spatial prioritization of locations in which placebased management should occur so that attention is focussed on those locations where resource investment will yield the greatest return for human well-being. Indeed, data are deficient in most locations for informing comprehensive and accurate analyses of trade-offs in ES management, and spatial prioritization is a crucial precursor to attempting such trade-off analyses so that data mining efforts occur in the most critical locations. Moreover, prioritization is essential because much ES management is 5 Page 2 of 14 F1000 Research 2012, 1:17 Last updated: 27 DEC 2012 conducted by government or non-government organizations (NGOs) that could potentially operate in many places. Given the important role that broad-scale prioritization can play in guiding decisions about where to conduct place-based ES management, a critical assessment of current prioritization approaches is warranted. Some schemes for identifying spatial priorities for managing ES are simple characterizations of biophysical processes and social demand, with little consideration of important information such as the availability of alternatives to ES for meeting human needs, threats to service provision, and the costs of management actions. Although fundamentally different to spatial prioritization for biodiversity conservation, spatial prioritization of ES may be guided by some of the key principles of the former. Spatial prioritization for conservation is well established and may be applied at coarse (e.g., biodiversity hotspots or priority ecoregions;8) or fine scales, identifying locations or actions in locations that are relatively more important for protecting biodiversity than other actions or other locations9. As with spatial prioritization of ES, spatial prioritization for conservation may help to identify locations where more detailed systematic conservation planning should be conducted, and is just one component of the planning process10,11. Spatial prioritization of ES differs from spatial prioritization for conservation because ES are valued primarily for their worth to humans, can be transferable across space (may not need to be protected at a specific location), are sometimes substitutable by human engineering, and service beneficiaries define the success of management actions. Yet, as with spatial prioritization for conservation, spatial prioritization of ES can guide decsions about local-scale planning and inform the allocation of resources from management agencies (e.g., World Wildlife Fund;12). Moreover, spatial prioritization for conservation is a useful starting framework for ES prioritization because the former is well entrenched in planning discourse13 and yields valuable lessons for ES management14. Current approaches to identifying spatial priorities for managing ES apply different prioritization methods (see Table 1), and developing more consistent and comprehensive methods is an important goal for future prioritization studies. We review past approaches to spatial prioritization of ES, identifying key aspects that should be considered in future analyses. At appropriate places we discuss the relevance of spatial prioritization for biodiversity conservation to spatial prioritization of ES because certain aspects, such as accounting for costs and threats, are common to both. We then demonstrate the importance of these aspects through a conceptual framework for prioritization that outlines an approach for managing the most vital ES for the least cost where they are most needed15. We illustrate the framework with a worked example using the ES of water provision. Egoh et al.14 reviewed the extent to which ES were included in conservation assessments (≈ identifying spatial priorities). Our work differs from Egoh et al. by assessing how ES priorities have been identified and how methods for prioritization should be improved. It also complements discussions of other aspects of ES management such as how to operationalize ES on the ground16, developing appropriate payments for services schemes (e.g.,17,18) or how to manage service provision at specific sites [e.g.,19,20]. Components of spatial prioritization The following are key elements to any conservation prioritization problem: biodiversity features [assets] that need protection (e.g., species or habitats); processes that threaten these features (e.g., habitat loss); a set of actions that may be effective at abating the threats (e.g., manage invasive species); and financial information specifying the cost of implementing each action, and the available conservation budget11. ES prioritization shares these elements; that is, identifying ecosystem features that supply services, threats to service provision, potential actions to ensure future supply of services, and the costs of these actions. Yet, prioritization of services requires at least the following additional considerations: the availability of alternative means of providing benefits supplied by services; the capacity of an ES to meet human demands; and scale of, and site dependency in, the delivery of services. While each of these factors may contribute to the economic valuation of an ES (i.e., captured by a metric such as dollar value) such complete and site-specific economic values are rare. Studies that estimate the financial value of ES facilitate the appreciation of services in widely understood terms, but this approach has well recognised limitations including the fact that financial values under-represent benefits to the poor as they have less capacity to pay than rich people21–23. Therefore, it is important to explore alternative approaches to identifying spatial priorities for ES management that circumvent some of the limitations of using financial values. Supply/benefits of ecosystem services Quantifying the benefits of protecting the supply of ES is generally most appropriately assessed in terms of the difference between protecting supply and not protecting supply. The advantages of protecting ES supply may be represented as benefits expressed in dollar values or avoided ecosystem damage (e.g., prioritizing locations with high soil erosion potential, but where vegetation cover ensures soil retention;24), or through quantifying the supply of services, often in biophysical units. The latter is the most common approach in broad-scale prioritization studies (Table 1). Biophysical quantities can include, for example, the amount of carbon stored in particular ecosystem types, water availability or supply, or fodder production. However, it is crucial to address also the issue of the level of biophysical quantity demanded by service beneficiaries. We refer to the level of human need for a service as ‘demand’, but recognise that this level changes with context and differs from the economic perspective of demand as the amount of a good or service that can be purchased at a given price. 5 Page 3 of 14 F1000 Research 2012, 1:17 Last updated: 27 DEC 2012 Ta b le 1 S tu d ie s id en ti fy in g b ro ad -s ca le s p at ia l p ri o ri ti es fo r p ro te ct in g e co sy st em s er vi ce s (p u b lis h ed f ro m 2 00 0– 20 11 ). S h ow n a re t h e ec o sy st em s er vi ce s in cl u d ed in t h e st u dy a n d h ow t h e au th o rs e xp re ss ed s u p p ly /b en efi ts , d em an d , t h re at s, c o st s o r av ai la b ili ty o f al te rn at iv es t o s er vi ce p ro vi si o n . B la n k ce lls r ep re se n t a la ck o f in fo rm at io n . 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