Descriptive results
After duplicates were removed, we screened 11,069 records by title and abstract. Common terms in the search string such as ‘gender’ and ‘resource management’ led to a high percentage of irrelevant results such as animal and plant studies. Hence, 10,936 records were excluded at the title or abstract level. Across all sources, we identified 133 studies for full-text review (Fig. 1). We were unable to locate three of the included studies. None of the three is likely to be relevant given that one is an introduction to a book, one is a conference report from a fisheries society meeting, and the other is a newsletter. Ultimately, 17 studies met the inclusion criteria. Of these, nine are peer-reviewed journal articles, four are book chapters, three are conference papers, and one is a thesis. All articles were less than 10 years old, and ten were from the last 10 years. ‘Additional file 2: full-text review results’ provides the references for the 17 included studies and the 116 excluded studies along with the reasons for exclusion.
Of the included studies, four were primarily qualitative [49–52] and 13 were primarily quantitative [8, 17, 18, 53–62]. Of the quantitative studies, the unit of analysis for all but three was the group, and the average sample size was 132 groups. Two studies used households as the unit of analysis [57, 58], and one used fish ponds (‘beels’) [59].
Geographically, the included studies are concentrated in South Asia. Twelve of the 17 studies are from India and/or Nepal. Latin America, East Africa, and southeast Asia had five studies in total.
We identified 14 forest articles and three fisheries articles (Fig. 2). Within fisheries, two studies addressed freshwater fisheries and one dealt with marine fisheries. ‘Additional file 3: study coding results’ gives the geographic and categorical data on each included study.
All 17 included studies identified improvements in local natural resource governance when women participated in the management of the resources, and three studies identified resource conservation benefits. Stricter rules (while still allowing for sustainable extraction), greater compliance with rules, greater transparency and accountability, and better conflict resolution were among the reasons for improvements. Additional file 4 summarizes the key findings from each included study.
Differences in the included studies
The most obvious differences among the studies lie in their design. Among the quantitative studies, seven use regression models with governance indicators as dependent variables and gender composition of groups as the explanatory variable [17, 18, 53–56, 59]. Among the remaining quantitative studies, the designs comprise before-after, control-impact quasi-experimental designs from a single site [57, 58], a before-after, control-impact quasi-experimental design across multiple sites [8], a before-after comparison [61], a control-impact comparison [60], and a frequency distributions of response for women’s, men’s, and mixed-gender groups with a least significant difference test for group averages [62]. For the qualitative studies, two use, inter alia, key informant interviews, focus-group discussions, and participant observations [51, 52], and one uses key informant interviews, focus group discussions, and secondary information [49]. The fourth uses ‘in-depth interviews and discussions with men and women separately’ [50].
Using the Maryland scientific methods scale to assess internal validity based on study design, 11 of the included quantitative studies were rated as having low internal validity given their study designs. One was rated as high because it measures before and after variables in multiple impact and control sites [8], and two studies had designs not covered by the Maryland scientific methods scale: one compared women-headed versus men-headed joint forest management committees [60] and a second compared, inter alia, frequency distributions of response for women’s, men’s, and mixed-gender groups [62]. For the four qualitative studies assessed with the CASP qualitative research checklist, one was high quality (8 out of 10 possible points) [52], one was medium (5 out of 10 possible points) [51], and two were low quality (<5 possible points) [49, 50].
Factors other than the gender compositions of resource management groups can also influence observed outcomes, and another difference among the included studies is which additional negative or positive influences on the outcomes are highlighted. The most frequently mentioned influencer is landlessness. Eight studies note that landlessness may make people more dependent on resources and less compliant with resource regulations [8, 17, 18, 50, 53, 54, 57, 58], and one study notes that including landless women in the governance structure increased regulatory compliance suggesting that governance inclusivity of the landless has benefits [17]. Given that the majority of the included studies were in India and Nepal, not surprisingly caste is a commonly mentioned influencer. For example, having Brahmins, the highest caste, present in a management group may benefit forest protection because they tend to wield traditional authority [8]. Yet a management group in a multi-caste community that is dominated by a high caste can also result in elite capture of the benefits [50]. Four studies highlight wealth among group members as an influencer that often improves resource governance and conservation outcomes [49, 50, 56, 57]. Two studies find differing influences from wealth [17, 18]. Education level of the household head is mentioned by two studies as both a negative and positive outcome influencer [56, 60], and two studies mentions high levels of political and/or economic inequality in a community as a negative influence [8, 56]. To reduce the influence of these factors, several studies use regressions models that control for the impact of factors other than gender and address the issue of omitted-variable bias [8, 17, 18, 53, 54].
Gaps in the available evidence
Forest management is comparatively well studied with 12 of the 17 included articles covering the topic, but most other common forest and fishery interventions are missing from the assembled literature. There are, for example, no included studies that cover reducing emissions from deforestation and forest degradation (REDD), reforestation, or fisheries co-management, and there is only one looking at fisheries protection [61], and two looking at the regulation of fishing [51, 59].