Nature-based Solutions Affecting Biodiversity in Headwater Catchments

: Assessment by Comparing Field Expertise with Scientific Literature (Northwest Europe) and Indicators (Belgium)

Abstract

The Earth’s climate is warming which is having a number of negative impacts on our environment. One of these negative impacts is the decline in biodiversity. Here we define biodiversity as the variety of life. A biodiversity-rich ecosystem is more resilient to climate change. One way to reduce the impact of climate change is to implement Nature-based Solutions (NbS). In this study we consider the synergies and trade-off effects of NbS on biodiversity. We focus on headwater catchments of lowland streams in NW Europe. The goal of those NbS is to mitigate flooding in headwaters. The question of this study is how NbS designed to mitigate flooding, affect the biodiversity in river catchments. To answer this question, we assess the effect at two spatial scales at two different methods. Firstly, we assess at a regional scale (North-West Europe) the field expertise of practitioners, on the effect of different NbS on biodiversity. We call this field expertise because these practitioners know their catchments and its biodiversity. They have been involved as stakeholders in the implementation of the NbS. The study area is the European Interreg 2Seas Co-Adapt project region where several NbS are being implemented in eight different catchments. Secondly, we assess the effect of NbS on biodiversity at a local scale (headwater catchment Barbierbeek, Belgium). At the regional scale we compare NbS field expertise on the ‘effect of NbS on biodiversity’ with what is stated in the scientific literature on this topic. We gather the ‘field expertise’ data from the practitioners in the field. We do this using a Consensus Decision Process (CDP) method, with an online session on brainstorming and voting. From the international scientific literature, we gather data on ‘effect of NbS on biodiversity’, using a method on Systematic Literature Review (SLR). We classified the different NbS on process and biodiversity impact. As a synthesis we compare and discuss both field observations and the scientific literature by this NbS classification. We assessed the effect of the NbS on biodiversity using this analysis. At the local scale – to validate the findings on field expertise of practitioners - we assess the ‘effect of NbS on biodiversity’ using biodiversity indicators in one of the Co-Adapt catchments: the Barbierbeek headwater catchment. Biodiversity indicators provide information to assess the state of biodiversity. As indicators, we look at the change in numbers of certain species in the catchment. To be able to test the effect, defined as the change in numbers of individuals of a species after implementation of NbS, we gather data on the biodiversity indicator over several years (from 2018 to 2022): 2018 is one year before the implementation of the NbS (2019), and 2022 is the last observation during the implementation period (2022). Looking at the results at a regional scale, we see that the experiences from the ‘field expertise by practitioners’ is similar to the results from analysis of scientific literature. Synthesis shows that of the implemented NbS that influence vegetation cover, runoff pathways, and connectivity enhance biodiversity. The results at the local scale are not as clear. Based on the biodiversity indicators, we have too little data. This goes for both pre- and postimplementation of the NbS. We cannot assess whether the implemented NbS in the Barbierbeek enhance biodiversity. Discussion: We show which NbS are most effective in enhancing biodiversity. But to be able to say something about the state of biodiversity by looking at specific species in a catchment, it is important to implement a monitoring plan. Co-creation is an important aspect of climate adaptation. Different NbS with the main goal to mitigate flooding are implemented in the valley of a catchment. This is only a limited part of the catchment area where biodiversity can be enhanced. Conclusion: Implemented NbS in a headwater catchment with the aim to mitigate flooding, may also enhance biodiversity. This is so for NbS that influence vegetation cover, runoff pathways, and connectivity. Enhanced biodiversity makes an ecosystem more robust to disturbances and the effects of climate change. The expertise on headwater catchments of lowland streams gathered in this study is additional to existing scientific literature. But we cannot conclude that biodiversity indicators help to assess pre- and post-implementation because we have insufficient data. An idea for future research on the effect of NbS on biodiversity is to include a monitoring plan around those indicators. A monitoring plan is needed to be able to measure any effect. When you are planning to implement NbS to mitigate the effect of climate change, it is important to also look at different synergies and trade-offs like biodiversity and drought.

Date of Award	11 Oct 2023
Original language	English
Supervisor	Angelique Lansu (Examiner) & Wilfried Ivens (Co-assessor)