The Environment Agency’s Chief Scientist’s Group has published a new and detailed 150 page report on the multiple benefits of nature-based solutions.

The findings in the report are summarised in a matrix that includes the type of NbS, and the catchment type (for example upland or lowland). The report includes a synthesis of available evidence of the effects of freshwater-related NbS on environmental outcomes in different types of English catchments.

Nature-based Solutions (NbS), which include a wide range of actions and interventions that protect and help sustainably manage and restore ecosystems, are increasingly being used to address issues such as water pollution or flooding.

Examples include land-use changes such as afforestation, river restoration techniques including floodplain reconnection, and sustainable agricultural practices like cover crops. 

Categories of NbS identified from the literature in the report include:

• Afforestation
• Constructed wetlands
• Temporary water storage features
• Buffer strips/zones
• Instream wood
• Peatland restoration
• Channel restoration
• Floodplain reconnection
• Sustainable Drainage Systems – Permeable pavement
• Sustainable Drainage Systems - Green roofs
• Sustainable Drainage Systems – Bioretention systems/rain gardens
• Sustainable soil management

The report says that more evidence is needed about where NbS are most effective, what other benefits can be provided, as well as their potential for unintended consequences. Robust evidence and confidence about NbS effectiveness is most likely to help target application and encourage appropriate uptake.

Five case studies illustrate the use of NbS across England and highlight some of the challenges faced by practitioners in implementing them.

The synthesis covered 135 studies, largely from peer-reviewed scientific literature. The monitored or modelled effects of NbS were considered under the following themes:

hydrological extremes (flood and low flow management)

water quality (nutrient/sediment management and physical/chemical/biological properties) biodiversity and habitat.

The review indicates that while generally NbS have multiple positive environmental effects,

there were also instances of conflicting evidence which may reflect the variable nature of NbS, particularly in how benefits, or disbenefits, may change over time, or be highly dependent on local context.

In some cases the derived benefits of NbS can be temporary with the ecosystem reverting back to its prior state over time, the report suggests.

It also found that different NbS have varying degrees of need for maintenance and that to be sustainable in the long-term, NbS need to be sustained by natural catchment processes.

It also highlighted specific catchment contexts where some NbS are likely to be less appropriate due to potential trade-offs and risks e.g.constructed wetlands on steep slopes where high run-off volumes could reduce pollutant removal efficiency.

In addition, the report says that the realisation of intended benefits can also be hampered by extreme weather and its effect on soils, vegetation, and river flows.

“In the face of climate change, NbS may need to be adapted to improve their resilience and remain effective under more extreme conditions,” the report suggests.

According to the review, there were gaps in the evidence under all themes, most notably the effects of NbS on biodiversity and habitats, with empirical evidence of the benefits for enhancing environmental resilience to low flow conditions also lacking. Cross-cutting evidence gaps include the effects of NbS at larger (for example, whole catchment) scales, and the effect of multiple NbS used in combination.

Other notable gaps include the effects of peatland restoration and assisted natural regeneration in lowland catchments and “a distinct lack of evidence relating to mitigation of groundwater

flooding.”

“The quantity and quality of evidence was highly variable between different NbS, catchment types, and environmental themes. In many cases, evidence was limited, inconclusive or implied,

highlighting a low level of confidence in their effectiveness,” ther report cautions.

However, the report concludes that whilst limited in places, the resulting matrixcan be used by practitioners to help make informed decisions on the suitability of NbS to different catchments.

Click here to download the report in full.