Riverwoods Evidence Review
A report from the Riverwoods Science Group
Scottish Wildlife Trust, Scottish Environment Protection Agency, James Hutton Institute, NatureScot, Forest Research, Buglife, Scottish Forestry, Tweed Forum, Marine Scotland, University of Highlands and Islands. Editors: Tanya Ogilvy, Nicola Melville, Roberto Martinez
Contributing Authors: Tanya Ogilvy, Nicola Melville, Roberto Martinez, Marc Stutter, Iain Sime, Mark Wilkinson, James Morison, Sam Broadmeadow, Liz O’Brien 2022
For the full report, please download the pdf attachment.
Executive summary
The Riverwoods initiative
The goal of the Riverwoods initiative led by the Scottish Wildlife Trust is to create a network of river woodlands supporting healthy and resilient river systems across the whole of Scotland funded by a diversity of financial sources including private and public funding.
Why invest in restoring river woodlands?
River woodlands are essential for healthy rivers and provide multiple benefits which help tackle the twin biodiversity and climate crisis. A SEPA project, including field surveys from 2015-16 found that over 50% of riparian vegetation on Scotland’s baseline river network is in poor condition without any trees or shrubs. Restoring Scotland’s river woodland is a priority and a key candidate for funding under conservation finance initiatives as a nature-based solution. Collating the available scientific evidence on the benefits of river woodlands provides an evidence base to justify financial investment in river woodlands for society, the economy, and nature itself.
Key aims of the evidence report
- To provide a broad indication of the most up-to-date scientific evidence underpinning the environmental benefits that river woodlands provide for Scotland.
- To present quantified evidence of river woodlands functionality.
- To classify the strength of the evidence based on the quality of studies to provide a level of confidence in woodland measures for investment purposes.
Audience & beneficiaries
The evidence in this technical science report will be valuable to a range of users including financial investors, businesses, land and river managers, Scottish Government and its agencies. The beneficiaries for specific benefits have been outlined in each benefit section.
River woodland types
The river woodland types included in the review are native riparian woodlands, floodplain woodlands, man-made riparian woodland buffers, gorge woodlands, natural large woody material and man-made large woody structures.
Results
A summary of the strength of evidence for river woodlands is presented in the table below. The strength of evidence is based on the quality of studies for each of the functions, with functions grouped into the benefits that river woodlands can deliver (column 1). The strength of the evidence ranges from very strong to weak. The majority of functions indicate a moderate to strong level of functionality based on empirical data quantifying a positive effect.
| River woodland
Benefit
|
Strength of evidence for functions of river woodlands |
|||
| Very strong | Strong | Moderate | Weak | |
| Clean water | Stabilising riverbanks
|
Controlling nitrogen pollution
Controlling phosphorus pollution Controlling excessive algae & periphyton Capturing sediment pollution Capturing pesticides |
Capturing pathogens | |
| Conserve Biodiversity & Ecosystems | Supporting aquatic processes | Supporting other species
Supporting river hydro-morphological processes and diversity |
Providing habitat connectivity & supporting genetic diversity | |
| Climate action: water stress & drought adaptation | Modifying local climate conditions: shading and cooling air | Modifying local climate conditions: hydraulic lifting | Maintaining water yields & low flows | |
| Climate action:
Flood risk alleviation |
Slowing the flow
Reducing coarse sediment delivery and siltation of channels |
|||
| Climate action: Carbon | Carbon sequestration & carbon storage | |||
| Clean air | Capturing air pollutants | |||
| Sustaining soils | Reducing soil loss | Improving soil health | ||
| Good human health | Exposure to river woodlands
Cooling air |
|||
| Wild fish and angling | Regulating local climate through shading
|
Providing food for fish | Improving habitat for fish with large woody material | |
| Sustain food production | Supporting pollination
Providing shelter & shade for livestock |
Providing fodder for livestock | ||
| Clean energy Biomass | Provision of biomass for energy | |||
Conclusions & recommendations
Specific recommendations have been provided for over-arching themes in the report and for healthy and resilient river systems and benefits to people (section 4.0). The key messages for the over-arching themes are as follows:
Design & location: River woodland measures need to be established with appropriate design and management to be effective and should be placed strategically within the catchment, in the right location(s) and at the right scale as this is critical for the delivery of the benefits.
Landscape scale approach: A landscape scale approach will improve delivery of many of the benefits and especially for clean water and flood alleviation. Sediment eroded from banks is often not a major source of polluting fine sediment, compared with sources direct from cultivated land.
Component of sustainable integrated land management: Land-use management has an impact on the quality of soil, air and water. River woodlands help safeguard our environment, whilst providing
Climate change resilience and diversification on farms. They also provide an income and support agricultural production via carbon, pollination, biomass and agroforestry.
Component of Scotland’s Nature Networks: Establishing a network of riparian and floodplain woodlands enables nature to adapt to climate change by supporting reproduction and genetic diversity of species and species migrations. River woodlands will also contribute to biodiversity on a landscape scale as an important component of a heterogeneous landscape.
Improve evidence: Improved evidence at catchment scale and over longer timescales will improve confidence in river woodlands as a nature-based solution. Estimations on the time it takes for benefits to be realised will be valuable for catchment planning, for example in identifying future needs of drinking water supplies or flood risk changes.
Next steps
- Communications work is required to tailor the scientific evidence for specific audiences, including the buyers and suppliers of river woodland ecosystem services. Plans are in place to deliver some of this through the Riverwoods partnership.
- A business case needs to be developed to enable effective delivery of river woodlands under the Riverwoods initiative, underpinned by bespoke business plans for each Riverwoods project. This is being addressed through the Riverwoods Investment Readiness Pioneers project being funded by the Esmée Fairbairn Foundation.
- Demonstration sites should be developed to show the pathway to investment ready projects and reduce uncertainty about outcomes for investors. Early work on this has now begun.
- The time that it takes for trees to establish to provide specific functions and benefits should be analysed and collated as it is an important consideration for investment and benefit calculations.
- Further work is required to review the most up to date decision support tools and guidance for implementation.
- River woodlands benefits should inform codes and standards supporting the development of natural capital markets and the shift towards a nature positive economy.
- This evidence report has identified a number of research and development gaps for river woodland implementation which should be assessed for prioritisation depending on business requirements.