Measuring agricultural sustainability in agroforestry systems

Abstract

Sustainability is an intuitively understandable but difficult-to-measure concept. Despite numerous efforts over the years to measure and integrate the ecological, economic, and social aspects of sustainability, a set of universally acceptable standards for measuring sustainability does not exist. The prevailing ecology-economy conflict, in which ecologists consider economics as a subset of environment, while economists view the environment and its benefits as part of the economy, adds to the difficulty. Agroforestry systems (AFSs), considered paradigms of sustainability, are faced with these difficulties when it comes to measuring and comparing various AFSs with one another or with other land-use systems. In ecological terms, the best criteria and indicators of AFS sustainability are ecosystem services, such as soil-fertility improvement, climate-change mitigation through carbon sequestration, and biodiversity conservation. As an example of the variability of one of these measures across studies, estimates of carbon (C) stored in AFSs range from 30 to 300 Mg C ha-1 up to 1 m soil depth; additionally, 0.29-15.21 Mg C ha-1 year-1 is estimated to be accumulated in aboveground biomass although most of it may not contribute to long-term C storage. In terms of economic sustainability, the principles and procedures of ecological economics and valuation of ecosystem services are useful approaches. Measurement of social sustainability, perhaps more challenging than measurement of the ecological and economic components, entails assessment of such social factors as policy, culture, and other socioeconomic indicators; a single measure of the combined manifestation of all these indicators is the adoption of improved practices by targeted land users. Standard procedures are available for measuring many of these indicators; however, most of them entail measurements taken over relatively long periods of time. Even if measurements and assessments are made rigorously, the ultimate benefit will depend on how sustainability is perceived and valued at all levels, from land users to national and international policy makers.