Desk study: “What is the state of knowledge on the role of biodiversity in the design, delivery, and benefits of Nature-based Solutions? A scoping review”
This study examines how biodiversity contributes to addressing social, economic and environmental challenges through nature-based solutions (NbS). It explores the links between biodiversity, ecosystem services and the benefits that people derive from different NbS approaches. In addition, and where available for a given NbS intervention, the study examines the links between biodiversity metrics and the achievement of NbS outcomes.
Overall, the study reveals biases in the available evidence base, related to the environments (e.g. 73% on terrestrial ecosystems) or types of ecosystem services considered (mostly agricultural/ provisioning), but also to the necessary diversity of biodiversity metrics used in case studies, which are often context-dependent (geographically and depending on the objectives of the NBS intervention). It was also noted that the lack of available comparisons between biodiversity-based interventions and other types of interventions (e.g. engineering) hampers the ability to assess aspects of effectiveness.
However, the elements collected provide preliminary answers to the general question posed:
- These studies provide evidence on different roles of biodiversity in NBS: direct material and non-material contributions to humans, regulating and supporting roles, although there is an evidence gap on the interaction between the two.
- About two-thirds of the studies indicated a positive effect of biodiversity on intended outcomes, while the remainder reported either a negative effect, no effect, or inconclusive or unclear results. The mixed or negative results were associated with the trade-offs between types of regulating, supporting, provisioning and cultural ecosystem services.
Identification of relevant case-studies
To meet the objectives of this desk study, a rapid scoping review was conducted following the systematic mapping methodology described by James et al. (2016). The literature search identified a total of 440 papers, of which 45 studies met the criteria established after the screening process. These studies provide evidence for different roles of biodiversity in NbS: direct material and non-material contributions to humans, as well as regulating and supporting roles.
Density mapping of keyword co-occurrences prior to screening revealed two major clusters: biodiversity and NbS. The lack of linkages between these clusters reflects the difficulty in identifying relevant studies that link the role of biodiversity in NbS outcomes during the literature search. This also reveals an evidence gap regarding the interaction between the two, consistent with the findings of Key et al. (2022). The study highlights a lack of biodiversity metrics that are relevant for considering the impact of biodiversity on NbS outcomes.
Density mapping of keyword co-occurrences analysis in the list of studies retrieved applying the search strategy before screening. The colour of a keyword indicates the degree of citations from yellow (highest number of co-occurrences) to blue-green (lowest number of co-occurrences).
Density mapping of keyword co-occurrences analysis in the list of studies retrieved applying the search strategy after screening. The colour of a keyword indicates the degree of citations from red (highest number of co-occurrences) to pink (lowest number of co-occurrences).
Distribution
The evidence captured in the 45 studies covers a wide range of climatic and geographical regions. However, there is a focus on terrestrial ecosystems, with 73% of the studies implemented in terrestrial ecosystems, mainly farming and agroforestry systems. Sustainable management (21 studies) was the most common type of NbS, followed by protection and conservation, created habitats, and restoration. This imbalance suggests that research on the role of biodiversity in agriculture outweighs that in other managed and anthropogenically influenced ecosystems, as well as other types of interventions and ecosystems. Few studies have focused on the role of biodiversity in other types of interventions, suggesting an emphasis on the material benefits of biodiversity, particularly in terms of food provision. However, different ecosystems and species groups can also address a range of pressing issues such as climate change, disaster risk, water scarcity and general human well-being.
Geographic distribution of the studies.
Metrics
Some studies (10) used a single biodiversity metric, while others (8) did not use a specific metric. The remaining studies used various combinations of several metrics, covering all the broad categories of biodiversity metrics. It is noteworthy that the same metrics can assess the role of biodiversity in different contexts, including ecosystem types and nature-based solutions. In addition, some metrics can provide insights across different broad metric categories. The most common biodiversity metrics across studies were ecosystem composition and diversity metrics. The limited use of perception/experiential knowledge may reflect the historical emphasis in the scientific literature on biophysical measurements rather than the role of biodiversity in human well-being. Meanwhile, the low frequency of conservation status and landscape structure metrics remains puzzling, as both are assessed and analysed in many regions.
Broad categories of biodiversity metrics used in the studies.
Linking issues and roles of biodiversity
All but one study discussed single-issue interventions, with a considerable number of studies focusing on agro-ecosystems, particularly food production, yield, and pest control. Evaluating the effectiveness of biodiversity’s roles in addressing these issues and designing fit-for-purpose NbS was not feasible because none of the studies included in this review directly compared biodiversity-based NbS with alternative approaches that primarily rely on non-living nature or engineered interventions.
Linking biodiversity and NbS outcomes
The study assessed the effect of biodiversity on NbS outcomes, considering study designs, biodiversity metrics, and taxa for a broad range of outcomes (such as climate change mitigation, well-being and health, food provision, and adaptation and resilience to disasters). While most studies (28) showed a positive effect of biodiversity on the intended outcomes, five studies reported a negative effect, seven showed no effect, and another five yielded inconclusive or unclear results. The mixed or negative results were associated with trade-offs between different types of regulating and supporting roles and contributions to people.
The role of biodiversity also depended on the intended outcomes and the metrics used, leading to variability between studies even for the same type of NbS, taxa, metrics or ecosystem. This shows that the role of biodiversity is context specific and related to the issues addressed by NbS and the intended outcomes. Given the limited available research on the role of biodiversity in similar types of NbS within similar ecosystems, this interpretation should be treated with caution.
Density mapping of keyword co-occurrences analysis in the list of studies retrieved applying the search strategy before screening. The colour of a keyword indicates the degree of citations from yellow (highest number of co-occurrences) to blue-green (lowest number of co-occurrences).
Density mapping of keyword co-occurrences analysis in the list of studies retrieved applying the search strategy after screening. The colour of a keyword indicates the degree of citations from red (highest number of co-occurrences) to pink (lowest number of co-occurrences).
Geographic distribution of the studies.
Broad categories of biodiversity metrics used in the studies.
