Systematic comparison of definitions and aims between Soil and Water Bioengineering (SWB) and Nature-Based Solutions (NBS)

Soil and Water Bioengineering (SWB) is a discipline established in the second half of XX century, finding its roots in ancient practices, which implies the use of vegetation and natural materials for natural hazards mitigation and ecosystem restoration. Nature-based solutions (NBS) is a recent collective term for solutions supported and/or inspired by nature to address climate-related challenges.

Although NBS cover a wide range of approaches based or inspired by natural processes and have many objectives in common with SWB, almost no attempts have been done so far to find overlaps and differences, which is needed especially when definitions are linked to legislations and funding mechanisms.

We present the results of a systematic comparison of NBS definitions, and other terminologies that fall under the NBS concept, with the definition of SWB. First, we identified applications that are related to the NBS umbrella concept, with their relative definitions, with a special focus on flood risk mitigation, ecosystem restoration, landslide and erosion mitigation. The applications analysed include: Watershed Management or hydraulic-forestry arrangements (WM), Nature-based Solutions (NBS), Green/blue Infrastructure (GI), Urban Forestry (UF), Ecological Engineering (EE), as well as Ecosystem-based Disaster Risk Reduction (Eco-DRR).

Secondly, a comparison matrix was proposed and developed. The matrix was developed by comparing the main aspects of SWB practice with the aims of the other NBS-related applications.

The structure of the matrix was the following:

• each row represents each of the 3 main aspects of SWB practices: namely "main aims", "fields of application" and "other objectives";
• the matrix columns designate all the other NBS-related terminologies, named above.

The three main aspects of the SWB discipline cover the following:

• main aims: the four main objectives of SWB; namely: technical, ecological, landscape and socio-economic objectives.
• fields of application: main domains of applications and fields of interventions;
• other objectives: the multi-purpose functions exerted by SWB.

Excerpts from relevant peer-review and grey literature on NBS were included in the matrix to cross-check the 3 main aspects of the SWB practice. We observed that SWB approaches have at least 2 "aims" in common with all the terms, particularly that all 3 main aspects are covered by the NBS definitions. In terms of "fields of application", the highest number of similarities are found between SWB and EE, and, to a smaller extent, WM, GBI and Eco-DRR.

In this work we conclude that SWB discipline can be recognized as a concept falling under the NBS unifying concept to prioritise nature to integrate climate change adaptation, mitigation and disaster reduction efforts. SWB overlaps and, in some cases, compliments many NBS-related terminologies. Thus, SWB can and should be recognized as having always been an NBS.