Limitations of our systematic map

The scope of our systematic map presented several limitations, which might be addressed in subsequent updates. First, while our search strategy was comprehensive, it was not exhaustive. Finite time and resources precluded additional searches of additional databases, forward and backward screening of the 1000+ included articles, and double assessment of the full dataset by two reviewers. Second, the search was limited to English language literature, although results from a search of Portuguese, Spanish and French language literature are forthcoming. Third, the map was focused on non-OECD countries which excluded research from 20+ developed countries. Expansion of the geographic scope to a global scale might allow interesting comparisons in interventions evaluated, outcomes measured and study designs used given variation in research capacity, economic prosperity and ecosystem health between developed and developing countries.

In addition to limitations to the scope of the search strategy, several caveats related to how data were synthesized and presented should be considered when interpreting results and using the systematic map for decision making. First, data extraction was intended to capture general characteristics for each article. This did not include assessment of the directionality or distribution of impacts observed by individual articles nor synthesis of average effect sizes for multiple articles as might be conducted as part of a more detailed systematic review or meta-analysis. Second, we extracted only limited information on the specific pathways and mechanisms by which conservation affects human well-being, directly or indirectly. In part this was due to the inconsistent and subjective nature of how these data were reported by articles as well as the volume of articles identified. Finally, high occurrence of evidence for a specific linkage or type of article does not equate to positive impact of an intervention on a particular outcome nor is evidence of higher levels of robustness. Our map gives an indication of robustness of the evidence, based on study design, but does not give a detailed quality appraisal of articles and how they deal with susceptibility to biases and heterogeneity of effects.

The extent and robustness of the evidence base was also affected by factors outside the design and scope of our study related to issues of accessibility, availability and bias in current research efforts. We were primarily limited to articles, documents and reports that were available electronically and distributed online. Books, monographs, and geographically discrete journals or those that targeting specialist groups, e.g., the Indian Forester, were less accessible from the library collections to which the research team subscribed. In addition, access to independent evaluations or reviews not published in peer-reviewed literature were dependent on commissioning organizations or researchers involved making these available and locatable electronically to the general public.

Gaps and biases in the evidence base

Beyond limitations in search strategy as discussed above, the current state of the evidence base is determined by gaps and biases in the distribution and extent of existing articles.

Limited or non-existent evidence, or gaps, on a specific linkage might be due to either a systemic bias in research efforts or rather to a lack of theory supporting a causal relationship between a specific intervention and outcome. The absence of evidence for some linkages might also indicate that a relationship is not plausible based upon existing theoretical thinking. Prominent linkages where we might have expected higher levels evidence to exist include articles measuring outcomes related to culture, security and safety, and human health. We posit several reasons for occurrence of these gaps. First, consistent time series data on more subjective outcomes, associated with dimensions such as culture, are rarely available at broad scales and often require primary data collection from individuals. Second, measurement of these outcome types involve lengthy timeframes, beyond the average program timeline, to observe demonstrable changes. Third, conservation might have a proximate or indirect effect on these types of outcomes, making it inherently more challenging methodologically to tease apart a specific interaction. Similarly, certain interventions associated with capacity building or empowerment within communities are often viewed as secondary activities intended to support other interventions, and thus might not be the target of monitoring. Fourth, the evidence base is skewed towards site level interventions in which direct, observable effects are more likely whereas larger more diffuse programs which potentially might have greater reach and impacts on well-being are more difficult to measure and thus less represented in the evidence base. Finally, the expertise required for analyzing linkages between many aspects of human well-being and conservation typically rest outside the realm of those working within conservation fields. Better understanding of health impacts for example would require knowledge on epidemiology, nutrition and health economics. Interdisciplinary collaboration is therefore essential when considering future research strategies to address these gaps.

Biases in research efforts have significant effect of the extent and distribution of existing evidence. Some biases, such as preferences for specific countries or biomes are well-documented, more broadly across the sector [20, 51]. Others such as the types of outcomes measured, interventions evaluated and study designs used are more specific to the research question at hand. Determinants of these biases are numerous, but include historical trends, individual researcher focus, and data availability. The lack of robustness of study designs, or lack thereof, was one of the most prominent biases observed in the evidence base. This trend has been observed by other related reviews [38, 43, 44]. Applications of rigorous impact evaluation methods in conservation remains limited relative to efforts more broadly on conservation performance measurement [4, 15, 16]. Efforts to date have been concentrated in countries with political support, consistent longitudinal datasets, and focus on interventions involving rapid applications, e.g., protected areas or payment for environmental services [33, 55].

Evaluations of conservation-related programs and policies have also focused first on biophysical outcomes with less attention to socioeconomic outcomes. Among the broader literature in environmental articles [1], recent reviews have observed few articles addressing joint effects between social and ecological outcomes [7, 43, 44]. A related bias observed in our study was the predominance of articles measuring specific aspects of well-being, e.g., economic and material. In many cases, these patterns may reflect the availability and accessibility of secondary quantitative datasets, e.g., USAID’s Demographic and Health Survey data, the World Bank’s Living Standards measurement surveys. There were few examples of articles measuring other important aspects of well-being, such as, culture and spirituality, freedom of choice and action. These aspects may be difficult to quantify but scales could be developed. They may be more suited for qualitative evaluation designs, e.g., stratified random sampling of household interviews, and thus require greater understanding of local contexts and data on tailored indicators collected from individual subjects. Better understanding of these dimensions may be particularly important given trade offs between financial and other outcomes, and because these may be distributed unequally across social strata, with the potential for widening social and health inequity [22].

Recommendations for conservation policy, practice and research

Interpretation of our results and their implications for conservation policy and practice are confined to findings from the included systematic reviews as these alone include critical appraisal of the direction and distribution of impacts between different interventions. Existing systematic reviews across this topic are targeted towards a subset of interventions (e.g., protected areas, community-based conservation and certification) and primarily in terrestrial biomes. Collectively, the reviews found conservation has both positive and negative effects on human well-being; yet benefits of specific interventions were inconclusive (e.g., community forest management, Bowler et al. [7]). A major implication is that existing evidence base is insufficient to determine the relative contribution of different interventions versus others to different aspects of well-being. As has been concluded by other recent reviews (e.g., [38]), the quantity and robustness of evidence needs to be dramatically increased to permit more concrete policy recommendations, and thus enable evidence-informed decision making. Our existing systematic map expands on these efforts by compiling a more complete range of interventions being applied across the sector and a more holistic overview of human well-being. This broad perspective helps to identify additional areas for further synthesis and critical frontiers for improved evaluation.

We recommend using this systematic map to support three follow-up actions: evidence synthesis, knowledge generation and theory development. Deciding which of these actions to take is dependent on occurrence and robustness of evidence across linkages identified in the evidence base. For linkages with high occurrence of evidence, further evidence synthesis using systematic reviews and, where possible, meta-analyses can provide information about directionality and distribution of impacts and in what contexts. For linkages with moderate occurrences of evidence and/or less robust evidence, we recommend implementing impact evaluations using robust study designs to boost internal and external validity. Where evidence is lacking or non-existent, exploration of underlying assumptions and existing theory is necessary. If a linkage is thought to be important, but no evidence exists, then it is important to examine whether a relationship between an intervention and an outcome is theoretically possible, and then to test this empirically with an impact evaluation. In the following sections, we discuss promising and priority questions related to each of these actions.

Promising and priority questions for synthesis

Our results suggest several areas in which evidence is sufficient for more detailed analysis and synthesis. The first relates to linkages between conservation and economic and material well-being. The high occurrence of evidence on these linkages confirms the continued predominance of economic constructs of poverty and development (see e.g., World Bank Group [62]).

Economic and material well-being have also been subject to a greater proportion of more rigorous impact evaluations and systematic reviews than other human well-being outcomes. Because these reviews vary in reliability (Fig. 10) and a number of new, robust articles have been undertaken since some of these reviews were published there is an opportunity to carry out additional syntheses on these linkages and expand their scope to marine and freshwater biomes. Synthesis of this evidence across intervention types opens up new possibilities for assessing the relative effectiveness of different (and emerging) strategies, such as market-based approaches, in realizing economic/material well-being goals, but also possible trade-offs with other aspects of well-being. Despite its value to theory, policy, and practice, there has been little to no comparative research of this kind to date. Such research is especially timely in the context of the Sustainable Development Goals and as the international community seeks the most effective means to reach the Aichi targets under the Convention on Biological Diversity.

The second area ripe for more detailed synthesis concerns governance and empowerment outcomes. There is sufficient evidence to examine links between these aspects of well-being and area and resource management. Though relatively few, there appears to be enough rigorous evaluations to explore this linkage. Exploration of the range of ways in which governance factors influence conservation human-well-being linkages is particularly pressing. Effective governance of natural resources might be a desired outcome of conservation policies and programs, but also a factor affecting the achievement of other social and ecological outcomes. There is a need, then, for synthesis of evidence on governance as an outcome. Specifically, those conservation programs that aim to target gaps or weaknesses in governance in their activities.

Promising and priority research questions

Further empirical evaluation is needed to document the magnitude and direction of particular conservation-well-being linkages, in particular for relationships commonly assumed in conceptual models, institutional strategies or global policy goals. Higher occurrence and more robust evidence on the contribution to sustainable development is an obvious priority given the recent launch of the Sustainable Development Goals. For example, surprisingly little evidence exists on the contribution of biodiversity conservation to Sustainable Development Goals 4 (Education), 5 (Gender Equality) 10 (Reduced Inequality), and 16 (Peace, Justice and Strong Institutions). The linkage between conservation and human health is an especially promising area for further research which might be informed by several ongoing initiatives such as the Health and Ecosystems: Analysis of Linkages (HEAL) collaboration (http://www.wcs-heal.org). While benefits of conserving wild populations for food provision and the flow of ecological processes upon which agriculture depends are promoted as part of ecosystem-based approaches [5, 36], the map reveals health outcomes from conservation interventions, such as trends in nutrition and disease risk, are surprisingly understudied.

In addition to improving evidence on a broader range of human well-being outcomes, other promising areas for research involve expanding the scope of evaluations to target less studied interventions such as market forces and livelihood alternatives. Understanding effects of these incentive-based interventions is important given greater interest in market-based approaches among NGOs (e.g., ACDI/VOCA, WWF) and foundations (e.g., new strategies by the Gordon and Betty Moore Foundation) as well as new models for implementation involving public–private partnerships (e.g., USAID and the Walt Disney Corporation in Alto Mayo, Peru). Reliance on evidence solely from traditional interventions limits the range of options for those planning and investing in conservation, and also presents a potential risk by not reporting unintended or even negative outcomes from new, but increasingly popular, interventions.

How the map should be used

In this paper, we present the first systematic effort to map the evidence on the relationship between conservation interventions and human well-being. By synthesizing existing evidence into a single, searchable resource, the map becomes, in effect, a ‘treasure’ map, simultaneously revealing rich seams of evidence ripe for synthesis as well as under-explored topics for targeted research. The evidence map allows conservation scholars, policymakers and practitioners to mine the evidence base to support a range of decisions. In the first instance, the map provides a ‘potted’ reading list for particular interventions or outcome types, potentially saving considerable time and resources for anyone interested in this topic.

For scholars, the map highlights immediate research priorities as well as emergent properties of the evidence base for further analytical investigation, such as associations between individual intervention-outcome linkages, or internal (i.e., research design) and external (i.e., political, social, ecological or economic context) factors that shape evidence quantity or quantity.

For policymakers, the map places specific interventions into a broader context by highlighting possible intersections between conservation, sustainability and economic development. Development agencies such as the World Bank or USAID, therefore, might use the map to assess the extent to which conservation might present an alternative strategy to achieving poverty alleviation to compare with existing strategies.

For practitioners, the map offers a tool to support design, implementation and monitoring of conservation interventions at local, national or global scales. While the map does not provide sufficient information to determine which interventions are most effective in which contexts (further synthesis would be required), it does provide a range of options to choose from, what outcomes they are associated with, and where they have been applied before. This might help validate existing efforts, highlight new or non-traditional approaches, and improve program design and implementation. The map might also be used to inform and guide monitoring of conservation programs by highlighting relevant indicators and tested methods for tracking them. Existing evidence can provide useful information on types of data and methods for monitoring specific outcomes. The map can also inform allocation of monitoring efforts. For example, where evidence is currently lacking and therefore impacts are uncertain, it might be beneficial to direct monitoring to these areas to help manage potential risks.

Our ambition for this systematic map is to improve the evidence base and specifically to encourage generation of stronger and more rigorous evidence on key linkages. We must also be realistic that a complete evidence base might never be possible and decisions are made with imperfect knowledge. All linkages are not equally important and the value of the map is its ability to help decision makers weigh the value of evidence between different linkages between conservation and human well-being. A next step to build on this map is thus provide guidance on how the current evidence base matches to existing evidence needs, and thus which linkages are highest priorities for establishing stronger evidence.