Biodiversity and the water cycle: can rewilding mitigate the impacts of hydrological extremes?

Lead Research Organisation: Queen Mary University of London
Department Name: Geography

Abstract

Managing and responding to floods and droughts in the UK demands vast amounts of public spending, and the frequency and severity of extreme high and low flows will increase under future climate change. Many parts of our river catchments have been heavily modified over long timescales, but there is now increasing evidence that working with natural ecosystem processes can deliver multiple environmental, social and economic benefits. The rewilding of degraded landscapes is increasing in popularity globally, and represents a vital tool in reversing biodiversity decline. The changes in biodiversity arising from rewilding also have the potential to drive wider benefits, but many of these remain largely unexplored.

Rewilding is the practice of returning modified landscapes to a wilder state and may include the reintroduction of missing animal species. Approaches to rewilding are wide-ranging, but the types of biodiversity change include natural regeneration of grassland, woodland and scrubland, increased biodiversity of soil-dwelling organisms, and reintroduction of large herbivores (e.g. cattle, deer, pigs) and keystone species that have disproportionately large effects on ecosystems relative to their population size (e.g. beavers, wolves). Many of the animals and plants that recolonise rewilding projects are effective 'ecosystem engineers': organisms that are capable of modifying habitats and flows of resources in ecosystems. The presence of ecosystem engineers has been linked with increased success of environmental restoration projects.

Importantly, the fundamental principles that underpin rewilding offer potential for much wider-ranging benefits to support freshwater and terrestrial natural capital assets and ecosystem services but understanding of these wider effects is limited. A key knowledge gap is understanding the capacity for rewilded landscapes to modify the water cycle and mitigate hydrological extremes. This would contribute to the evidence base for the economics of biodiversity by delivering more effective water resource and water hazard management.

Rewilding, by nature and scale, will alter key elements of the water cycle. Changes to soils, vegetation and river-floodplain systems arising from rewilding will alter the movement and storage of water within landscapes. If rewilding outcomes mean that water takes slower routes through the landscape, it has the potential to make important contributions to flood and drought mitigation. Our project will explore the role that biodiversity gains from landscape rewilding play in modifying the water cycle and mitigating the impacts of hydrological extremes. We will use a review of the existing evidence from rewilding projects, other forms of landscape restoration and sustainable land management, and semi-natural ecosystems, to assess the state of the evidence for key types of rewilding-driven biodiversity change, and identify knowledge gaps and future priorities. In particular, we will answer the questions:

1. How does rewilding alter hydrological processes?
2. How do these effects differ across rewilding scenarios and environmental settings?
3. To what extent have these changes delivered measurable effects on floods and low flows?
4. Where are the gaps in knowledge across questions 1 to 3?

Answering these questions will determine the ways in which rewilding influences hydrology and hydrological extremes, support decision-making in rewilding practice across public and private sectors and inform future research priorities and improved monitoring of rewilding programmes.

Publications

10 25 50
 
Description Our systematic review and meta-analysis revealed:
A distinct lack of research on the hydrological outcomes of landscape rewilding
Drawing data from analogue systems, there is twice as much evidence available to explore effects on high flows (floods) compared to low flows.
Few studies address high and low flows simultaneously.
Available evidence supports an attenuating effect across different rewilding elements trajectories, but with variations in the magnitude of effect and some exceptions.
The evidence for a mitigating effect on low flows is very limited and more complex, with differing effects according to the type of landscape change.
Exploitation Route We are using the data set to explore the influence of different rewilding trajectories and effects on hydrological processes in greater detail via a PhD project.
The outputs reveal a key knowledge gap in rewilding monitoring and provide a research agenda for future rewilding projects and scientific studies.
This includes new studies simultaneously addressing the impacts of landscape rewilding on high flows and low flows.
Sectors Agriculture

Food and Drink

Environment

 
Description Our findings have led to invitation to join the Rewilding Britain Monitoring Framework Advisory Board. Involved attending an expert workshop on 10th May 2023 where PI Harvey and Co-I Henshaw directly contributed to the development of the metric framework. The outcome was the inclusion of hydrological parameters and vegetation complexity parameters a key suits of metrics within the framework.
First Year Of Impact 2023
Sector Environment
Impact Types Societal

 
Description Leverhulme Research Fellowship
Amount £59,888 (GBP)
Funding ID RF-2022-284\4 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2022 
End 06/2023
 
Description NERC Growing Shoots Partnership and application co-creation bursary
Amount £25,000 (GBP)
Funding ID NE/Y005821/1 _Growing Shoots 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 01/2024 
End 03/2025
 
Description NERC Knowledge Exchange Fellowships
Amount £94,052 (GBP)
Funding ID NE/Y005155/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2024 
End 04/2026
 
Description NERC Knowledge Exchange Fellowships
Amount £96,393 (GBP)
Funding ID NE/Y005163/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2024 
End 04/2024
 
Description Chair of Nature Group for Monitoring and Evaluation: Enfield Chase Landscape Recovery Project 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact PI Harvey was invited to chair this advisory group. The purpose is to provide guidance and specialist direction for the monitoring, evaluation and learning strategy deliverables of the Enfield Chase Landscape Recovery Project Development Phase (PDP). The group will be led by Thames21 who will work with stakeholders in the group to develop and agree on the monitoring, evaluation and learning strategy deliverables within the agreed timeframes for the project.
Year(s) Of Engagement Activity 2023,2024
 
Description Membership of Rewilding Britain's Monitoring Framework Advisory Board 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact PI Harvey and Co-I Henshaw have been invited to participate in this advisory board. The purpose of the board is to bridge the research - practice interface by advising on a suite of science-led, standardised metrics and appropriate, pragmatic methods to support members of Rewilding Britain's Rewilding Network who wish to collect data to support their rewilding projects.
Year(s) Of Engagement Activity 2023,2024