Engineered in-stream structures are often installed to increase salmonid abundance, either for commercial gain in fisheries or for conservation purposes in degraded habitats. Having been in widespread use for the last 80 years, at an estimated cost of hundreds of millions of U.S. dollars each year, the effectiveness of these structures is still widely debated in the literature. Many studies of varying quality have been undertaken that attempt to address this issue, but it has proved difficult for practitioners to develop a consensus regarding the utility of these structures, despite their continued use. Systematic review methodology was used to formally synthesize empirical evidence regarding the effectiveness of engineered in-stream structures as a management tool to increase salmonid abundance. Meta-analysis shows that evidence regarding the effectiveness of in-stream devices is equivocal. Heterogeneity is significant both for population size and local habitat preference. This heterogeneity is related to stream width, with in-stream devices being less effective in larger streams. Consequently, widespread use of in-stream structures for restoration, particularly in larger streams, is not supported by the current scientific evidence base.

Background: This paper provides guidance about how to plan, prepare, conduct, report, amend or update a systematic search. It aims to contribute to a new version of the Collaboration for Environmental Evidence (CEE) Guidelines for Systematic Reviews in Environmental Management, and the methods we describe are likely to be broadly applicable across a wider range of topics. In evidence synthesis, searches are expected to be repeatable, fit for purpose, with minimum biases, and to collate a maximum number of relevant articles. Failing to include relevant information in an evidence synthesis may lead to inaccurate or skewed conclusions and/or changes in conclusions as soon as the omitted information is added. Method:The paper takes into account similar documents produced by the Cochrane Collaboration and the Campbell Collaboration, including necessary adjustments for environmental policy and management, and the current version of the CEE Guidelines (version 4.2, 2013). Where possible this guidance is based on evidence from research, and in its absence on expert opinion and experience. Results:Here we aim to provide guidance on the optimal search structure as the basis on which any evidence synthesis should be built. Conclusion:It is aimed at all those who intend to conduct systematic evidence synthesis, including reviews and Ph.D. thesis.

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The dangers posed to wooded environments from tree pests introduced by the expansion of international trade in live plants and the continued use of wood packaging in transporting materials have been widely accepted. A lack of awareness of the issues amongst key stakeholders involved in the movement of these materials can hamper an effective response as their unaltered behaviours continue to have unintended consequences. Better communication and engagement is needed to enrol this wider range of actors, such as plant buyers, traders and woodland owners, in preventative action or mitigation of tree pest impacts. However, as this review paper shows, current published evidence on awareness levels and effective engagement methods is limited, and lessons must be sought from research into other closely related issues such as invasive plants. We provide a summary of this available evidence, related to key stakeholder groupings, their levels of awareness and current modes of information provision and reception. It show what can at best be described as mediocre levels of awareness, and highlights the role of traditional media, such as television and newspapers, as sources of information. It further notes the urgent need for research to more fully map the tree health stakeholder landscape and to further our understanding of how to increase awareness and effect changes in behaviour.

Given the proliferation of primary research articles, the importance of reliable environmental evidence reviews for informing policy and management decisions is increasing. Although conducting reviews is an efficient method of synthesising the fragmented primary evidence base, reviews that are of poor methodological reliability have the potential to misinform by not accurately reflecting the available evidence base. To assess the current value of evidence reviews for decision-making we appraised a systematic sample of articles published in early 2015 (N=92) using the Collaboration for Environmental Evidence Synthesis Assessment Tool (CEESAT). CEESAT assesses the methodology of policy-relevant evidence reviews according to elements important for objectivity, transparency and comprehensiveness. Overall, reviews performed poorly with a median score of 2.5/39 and a modal score of zero (range 0-30, mean 5.8), and low scores were ubiquitous across subject areas. In general, reviews that applied meta-analytical techniques achieved higher scores than narrative syntheses (median 18.3 and 2.0 respectively), as a result of the latter consistently failing to adequately report methodology or how conclusions were drawn. However, some narrative syntheses achieved high scores, illustrating that the reliability of reviews should be assessed on a case-by-case basis. Given the potential importance of reviews for informing management and policy, as well as research, it is vital that overall methodological reliability is improved. Although the increasing number of systematic reviews and meta-analyses highlight that some progress is being made, our findings suggest little or no improvement in the last decade. To motivate progress, we recommend that an annual assessment of the methodological reliability of evidence reviews be conducted. To better serve the environmental policy and management communities we identify a requirement for independent critical appraisal of review methodology thus enabling decisionmakers to select reviews that are most likely to accurately reflect the evidence base.