1 Ecosystem-based.cdr

The ecosystem approach is a widely accepted framework for natural resource management and has been adopted by the Convention on Biological Diversity (CBD) as the primary framework for action under the convention. The ecosystem approach, as defined by the CBD, is underpinned by a set of twelve principles and points of operational guidance that are intended to aid the implementation of the approach. However, these are overarching principles and implementing an ecosystem approach in practice requires practical tools for local managers and policy makers that embody the principles but are appropriate for the challenges faced at a local level. Here, we present a set of indicators, and a toolkit to aid their application, that are intended to support the implementation of the ecosystem approach in the management of riverine ecosystems in Ghana. The application of the indicators is illustrated using data gathered for the Densu, Ayensu and Birim catchments. requires not only good scient i f ic understanding of ecosystem dynamics and environmental controls, but also the ability to influence human actions taken at a local level throughout the whole basin, not just in riparian areas. Such influences are invariably linked to patterns of agriculture and various economic and social policies not directly connected with concerns for the riverine environment. The ecosystem approach provides the concept and outline structure by which all these dimensions can be considered within a single framework with a better chance of succeeding in an improved balance of conservation and sustainable development objectives. Twelve principles and additional notes of guidance that have been distilled through a long process of consultation and development underpin the approach. In further endorsing the approach the Conference of Parties (COP) of the CBD recommended its implementation with appropriate adaptation to local, national and regional conditions. It also requested the identification of good case studies and the implementation of pilot projects (which could apply from the outset rather than retrofitting the logic and methodology of the EA). The COP also expressed the need for more awareness of the approach, experiencesharing and capacity building necessary for implementation. Above all, whilst there is increasing knowledge of what the ecosystem approach is trying to achieve there is still a major gap in the understanding of exactly how to do it. A suite of indicators of riverine ecosystem health, and tools for its application, has been developed for Ghana in order to address some of these gaps and support the implementation of the ecosystem approach in the management of riverine ecosystems. Riverine ecosystem indicators No single indicator can provide an adequate picture of ecosystem quality so a suite of indicators has to be chosen that gives a general overview of the condition of the river. The selection of metrics and parameters is the key challenge in developing a suite of indicators that reflect ecosystem quality in rivers. There are a large number of potential parameters or processes that could be measured but not all are suitable as indicators. Key considerations include the accuracy with which they can be measured and their spatial and temporal variability as, generally, indicators are infrequently measured in space and time and therefore highly variable ecosystem attributes may not be appropriate as indicators. The purpose of the indicators is also an important consideration. Potentially, indicators can be used to give a one-off assessment of ecosystem quality, to monitor changes over time, to provide early warning of problems, act as a communication tool or assess progress towards targets. In practice, the choice of indicators has to reflect the pract ical i ty of measurement , the information they can convey and the availability of standards or reference data to show how good or bad a particular value is. Compatibility with existing methodologies (e.g. water quality indices) is also an important consideration. Yli-Viikari et al. (2007) review quality criteria for indicators. Some commonly identified criteria for indicators include: • Measurable (availability of data and cost effectiveness of collection) • Analytically sound and based on science • Well documented • Responsive to changes in ecosystem state • Ability to adapt to different spatial scales of assessment; • Existence of a reference value • Easy to interpret • Policy relevance In addition to the general considerations of selecting good indicators, if indicators are to support the implementation of an ecosystem approach to management there are a number of additional considerations. The connectedness of running waters with their floodplains and catchments must be considered, as does information on the broader landscape-level management (Boulton, 1999). The principles of the ecosystem approach stress the importance of considering connectedness and the scale at which process operate. Water chemistry has been traditionally used in industrial countries as a measure of freshwater quality, but used in isolation it has several drawbacks and can only form a component of indicators based on an ecosystem approach. Only a few variables, out of several hundred thousands (including many persistent organic pollutants (POP) by which natural and polluted waters vary) are measured, so only a limited picture is obtained; water chemistry is relatively expensive to measure; many variables, including those of the most important polluting substances, vary greatly over short periods, usually much shorter than the sampling intervals; and for many chemical v a r i a b l e s ( i n c l u d i n g p H o x y g e n concentration, conductivity, major ions like calcium, sodium, chloride and sulphate) a simple standard has no meaning. A significant change will have meaning but can only be seen from a run of several years of observations. Much more useful and accurate information of the state of a water body is obtained from land use and ecological observations. Chemical variables are, however, included in the indicator scheme presented here to ensure compatibility with existing data. With these criteria, and the requirements of the ecosystem approach in mind, the indicators proposed here are intended to allow an ecosystem-based assessment of the overall condition of a river in a Ghanaian context. As such, they are intended to be relatively easily quantified used ecological field observations, simple measurements and ecological sampling. The indicator set also includes some water chemistry metrics but for the most part these have been kept as simple as possible and can be quantified using cheap and easily obtained equipment (e.g. temperature, conductivity). As a whole the indicator set encompasses catchmentscale indicators of disturbance, water chemistry and ecological indicators it reflects an Ecosystem Approach. Table 1 outlines the indicators adopted for this scheme and gives a brief outline of the rationale for including the indicator in the assessment scheme. A more complete description of the indicators and the caveats for their use can be found in the information sheets that accompany the indicators. The set of indicators developed here are intended to take into consideration the general requirements of ecosystem state indicators outlined above and to take into account the requirements of the ecosystem approach. The indicators incorporate an ecosystem approach in that they include consideration of the condition of the wider catchment, not just the location being Linstead et al.: Ecosystem-based Indicators for Monitoring the Status of Rivers in Ghana 3 2 West African Journal of Applied Ecology, Vol. 21 (3), 2012