Despite the aim of conservation science being to inform and guide management (Meffe et al. 2006), decision makers report that it can be difficult and time-consuming to access available science (Fazey et al. 2004; Zavaleta et al. 2008) and that research findings can be challenging to interpret (Pullin & Knight 2005). Debate in the literature and conflicting research findings can also cause managers to mistrust scientific information (Young & Van Aarde 2011). Compounding these challenges, the peer-reviewed literature often does not address questions of direct relevance to conservation managers (Whitten et al. 2001; Fazey et al. 2005) or deliver information when needed (Kareiva et al. 2002; Linklater 2003). These impediments to using science to guide practice have contributed to the poor use of empirical evidence to inform management decisions (Sutherland et al. 2004; Cook et al. 2010).
The challenge of translating science into practice is not unique to conservation but is common to many applied disciplines (Pfeffer & Sutton 1999; Pullin & Knight 2001). Concern about the lack of evidence in medical practice (Forsyth 1963; Cochrane 1972; Maynard & Chalmers 1997) stimulated an evidence revolution (Pullin & Knight 2001) that promoted randomized, controlled trials as the standard for credible evidence (Stevens & Milne 1997). To help practitioners manage the rapid increase in available evidence (Chalmers 1993), systematic reviews were developed as a tool to collate (systematically search the available literature), filter (identify credible sources of evidence), synthesize (analyze the body of evidence to determine the overall effect of an intervention), and disseminate the evidence for the effectiveness of potential and currently used treatment options on a topic for practitioners (Higgins & Green 2011). The rigorous methodological and statistical protocol associated with systematic reviews minimizes bias and improves their transparency and repeatability (Pullin & Stewart 2006; Newton et al. 2007). These factors make systematic reviews more comprehensive and less open to potential bias than other review formats that summarize the literature in an unstructured way (e.g., narrative reviews) (Roberts et al. 2006). A distinct focus on making recommendations for management and a systematic search of both the peer-reviewed and gray literatures generally distinguish systematic reviews from traditional meta-analytical studies. The practice of systematic reviews has been widely adopted in medicine, health sciences, education, criminology, and several other disciplines (Hansen & Rieper 2009).
The benefits of an evidence-based approach to medical practice have led several authors to promote systematic reviews as a tool for integrating science into conservation practice (e.g., Pullin & Knight 2001; Fazey et al. 2004; Sutherland et al. 2004). Systematic reviews facilitate evidence-based conservation practice by providing managers with an overview of relevant, trustworthy empirical evidence pertinent to a decision (Pullin & Stewart 2006). The evidence movement has been instrumental in highlighting the importance of evaluating the effectiveness of management interventions (Ferraro & Pattanayak 2006) so that decision makers do not waste time and money on ineffective or potentially harmful management interventions (Pullin & Knight 2001). By combining the replicates from multiple studies, systematic review can also maximize the value of primary research, generating greater explanatory power, which may reveal effects not detected by the original individual studies (Mulrow 1994).
To facilitate systematic reviews and make them freely available to managers, the Collaboration for Environmental Evidence (CEE) (www.environmentalevidence.org) was developed (Pullin & Knight 2009). The collaboration was modeled on the Cochrane Collaboration for medical practice and the Campbell Collaboration for social programs. The CEE has developed detailed guidelines (Pullin & Stewart 2006; CEBC 2010) to assist authors wishing to conduct systematic reviews of conservation interventions.
With evidence-based conservation being embraced by the conservation community as a desirable approach to decision making, it is timely to review the benefits to conservation practice arising from systematic reviews. We examined how the method of systematic review has been applied to evidence about the effectiveness of conservation interventions and the benefits they have provided to conservation practice. We measured the level of guidance systematic reviews offer conservation managers and quantified the types of conservation questions being addressed; geographic and taxonomic breadth of reviewed topics; and the quantity of primary research available in a format suitable for systematic review. We considered the benefits to environmental management arising from systematic reviews and how systematic reviews might be improved.