J. A. Webb

Analyzing cause and effect in environmental assessments: using weighted evidence from the literature

Abstract.  Sound decision making in environmental research and management requires an understanding of causal relationships between stressors and ecological responses. However, demonstrating cause–effect relationships in natural systems is challenging because of difficulties with natural variability, performing experiments, lack of replication, and the presence of confounding influences. Thus, even the best-designed study may not establish causality. We describe a method that uses evidence available in the extensive published ecological literature to assess support for cause–effect hypotheses in environmental investigations. Our method, called Eco Evidence, is a form of causal criteria analysis—a technique developed by epidemiologists in the 1960s—who faced similar difficulties in attributing causation. The Eco Evidence method is an 8-step process in which the user conducts a systematic review of the evidence for one or more cause–effect hypotheses to assess the level of support for an overall question. In contrast to causal criteria analyses in epidemiology, users of Eco Evidence use a subset of criteria most relevant to environmental investigations and weight each piece of evidence according to its study design. Stronger studies contribute more to the assessment of causality, but weaker evidence is not discarded. This feature is important because environmental evidence is often scarce. The outputs of the analysis are a guide to the strength of evidence for or against the cause–effect hypotheses. They strengthen confidence in the conclusions drawn from that evidence, but cannot ever prove causality. They also indicate situations where knowledge gaps signify insufficient evidence to reach a conclusion. The method is supported by the freely available Eco Evidence software package, which produces a standard report, maximizing the transparency and repeatability of any assessment. Environmental science has lagged behind other disciplines in systematic assessment of evidence to improve research and management. Using the Eco Evidence method, environmental scientists can better use the extensive published literature to guide evidence-based decisions and undertake transparent assessments of ecological cause and effect.

An Economic Framework for Sharing Water Within a River Catchment

A framework for sharing a limited quantity, but also a variable quantity, of water between irrigation and the environment to maximize social wellbeing is developed and illustrated. The optimal water allocation equates the marginal social value of water across different uses. A simplified illustration allocates water from the Goulburn River in northern Victoria, Australia, between environmental water to increase numbers of Golden Perch (GP) fish stocks and irrigation demand for water for dairy farmers. The value of water for GP is developed using a combination of fish numbers as an ecological response function of water and Choice Model estimates of willingness to pay by Victorian households for improved fish stocks. Irrigation demand for water by dairy farmers is developed using a Linear Programming study. The complex ecological response functions require a numerical search model to evaluate the socially efficient allocation of water between the different uses. The shadow price of water as optimally allocated between the environmental and agricultural uses is developed as seasonal water availability varies. Further development of the framework could include identifying dependencies within the ecological responses and incorporating multiple ecological and agricultural responses in an expanded model. The policy implications include information on the socially efficient allocation of limited water between irrigation and the environment and the value of water when shared optimally between uses.

Environmental Flows and Eco-Hydrological Assessments in Rivers

Abstract Strong national water policy requiring governments to protect environmental water has accelerated efforts to plan and deliver environmental flows across Australia since the mid-1990s. This chapter describes environmental flows assessment methods applied over this period including: hydrological methods widely used at the basin and regional scales, and holistic methodologies used at reach or river scale. The chapter also describes the challenge and opportunities in providing better prediction of ecological responses to changing flow regimes, a key requirement for robust environmental flow planning.

Systematic causal inference and knowledge transfer between science and policy: Eco Evidence in water management

Abstract Effectively transferring complex scientific ideas into the policy domain is a serious challenge, but an essential one given the important role of science in assessing the implications of a changing climate and resulting water shortages in Australia. Eco Evidence, a method for conducting systematic reviews of the scientific literature using causal criteria analysis, was developed for the eWater Cooperative Research Centre to help bridge this gap between science and policy. It provides a transparent and repeatable method for assessing the strength of the available scientific evidence regarding particular management actions. However, if evidence is used to justify decisions rather than to provide options and likely outcomes of these options to stakeholders, its effectiveness can be undermined. By drawing on interdisciplinary theories of uncertainty in the science-policy arena, this paper demonstrates how Eco Evidence can be used in evidence-based practice in a manner that does not interfere with the effective participation of a range of stakeholders in the decision-making process.