SUMMARY Sustainable indicators have become popular tools by which policymakers can assess progress towards a more sustainable agriculture. Varying approaches to defining sustainability lead to disagreement about the value of indicators and yet some form of measurement is required so that society can judge the effects of policy. Environmental and social problems and their causes span national boundaries. An international framework for assessing agricultural activities, their effects and the pressures that drive those activities is therefore required. However, a guiding principle of the UN Agenda for Sustainable Development is that global problems require local action. Thus, indicators must provide information for policymakers as well as guidance for farmers and other practitioners. Many indicator programmes currently proposed do not provide this level of guidance as no evaluation as to what level of activity is sustainable has been agreed. A model is presented, to show how scientific and political or participatory approaches may be combined to meet the multiple objectives of involving people, maintaining scientific integrity and providing guidance for policymakers and practitioners alike. 相似文献
Identifying source information after river chemical spill occurrences is critical for emergency responses. However, the inverse uncertainty characteristics of this kind of pollution source inversion problem have not yet been clearly elucidated. To fill this gap, stochastic analysis approaches, including a regional sensitivity analysis method, identifiability plot and perturbation methods, were employed to conduct an empirical investigation on generic inverse uncertainty characteristics under a well-accepted uncertainty analysis framework. Case studies based on field tracer experiments and synthetic numerical tracer experiments revealed several new rules. For example, the release load can be most easily inverted, and the source location is responsible for the largest uncertainty among the source parameters. The diffusion and convection processes are more sensitive than the dilution and pollutant attenuation processes to the optimization of objective functions in terms of structural uncertainty. The differences among the different objective functions are smaller for instantaneous release than for continuous release cases. Small monitoring errors affect the inversion results only slightly, which can be ignored in practice. Interestingly, the estimated values of the release location and time negatively deviate from the real values, and the extent is positively correlated with the relative size of the mixing zone to the objective river reach. These new findings improve decision making in emergency responses to sudden water pollution and guide the monitoring network design.
