Floodplain grassland restoration
16th November 2023
Ellie MacDonald is our Floodplain Conservation Officer for the Oxfordshire–Buckinghamshire Freshwater Network. The project focuses on the role of smaller, peat-dominated wetlands, floodplains, wet grasslands and small waters in sequestering carbon in the landscape. Through habitat creation and restoration, it is also helping us to build the Freshwater Network – a national network of wilder, wetter, cleaner and connected freshwaters.
This summer Ellie carried out floodplain grassland restoration using species-rich green hay, but what are floodplain grasslands and what is green hay? Ellie answers some questions about floodplain grassland restoration and why it’s so beneficial for biodiversity.
What are floodplain grasslands?
Floodplains are areas of low-lying land adjacent to rivers that flood seasonally. The grassland areas that are found on floodplains can be very species-rich thanks to the natural disturbance that seasonal flooding provides, from the nutrients provided by flood water, and disturbance by grazing animals or hay making.
Why is Freshwater Habitats Trust interested in protecting them?
At Freshwater Habitats Trust we are developing The Freshwater Network which is an approach to the conservation of freshwater biodiversity that aims to protect freshwater wildlife by creating a national network of unpolluted and connected freshwater landscapes. This includes small waterbodies and wetland habitats, historic floodplains, and wetland opportunity areas.
Floodplain habitats are a vital part of the freshwater network across England and Wales, and they have a rich wetland heritage, being shaped by low input management, traditionally with annual mowing and grazing which created the type of diverse wetland habitats we aim to protect and restore. However, these floodplain areas have been degraded and disconnected by threats such as the loss of traditional management, drainage, increasing nutrient pollution, and the disconnection of wetland habitats. It is estimated that nearly half of historic floodplains are no longer connected to river systems and that only 11% of floodplains support semi-natural habitat (Lawson et al., 2018).
How does this work link to green hay? And what is green hay?
To restore these degraded floodplain habitats, we need to improve their condition and bring back the species that may have been lost from them. One way of restoring floodplain grasslands is to use a method known as ‘green hay’. Green hay is hay taken from species-rich grasslands as part of the annual hay cut. When this is then spread on your chosen floodplain restoration area, it brings the seeds of native wildflowers and grasses back to the site, improving the species diversity of the floodplain grassland.
Why did you become involved in working with green hay? Is this a first for Freshwater Habitats Trust?
To further the protection of wetland habitats, expand the freshwater network, and boost freshwater biodiversity we are exploring multiple methods of carrying out habitat restoration. Using green hay to restore floodplain grasslands is one such method and this is the first time that Freshwater Habitats Trust have used this approach. Green hay is commonly used in nature conservation projects to restore floodplain grasslands (Rothero et al., 2020) and there is an increasing abundance of knowledge shared about this process. Armed with this knowledge, and the experiences gathered and shared by partner organisations, we carried out our first application of green hay in summer 2023.
Where have you used Green Hay? Who did you work with to make this possible, and what is the process of creating Green Hay?
We used green hay at three sites across Oxfordshire and Buckinghamshire as part of the Natural England funded ‘Nature returns’ project based in these two counties.
The first step in the green hay process is to find a suitable donor site from which to get your species-rich hay. For this project our donor sites were floodplain grasslands managed by Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust and The Parks Trust, in Milton Keynes.
Once a donor site has been found and the hay-cut season is approaching, the next step is to prepare your restoration site by making sure that the grass is very short and that there are enough bare areas that seeds can reach the soil to germinate. This preparation occurs around a week before you expect to cut the donor site, which then happens as part of the annual hay cut of the donor site. The hay is then moved from the donor site and spread on the restoration site on the same day whilst it is still fresh and ‘green’. This delivers the grassland seeds that have been lost from the restoration site due to the degradation and fragmentation of floodplains over time.
The process requires collaboration between all parties involved in the organisation and delivery of the work. Clear communication between all parties is key as the timings of green hay spreading are tightly linked to the weather, the progress of the donor hay growth, and the availability of the people involved in carrying out the work. The expertise and in-depth knowledge provided by these partner organisations is invaluable, highlighting the importance of collaborative working and knowledge sharing in nature conservation.
What benefits do you hope to see? Are there any species you hope to bring back?
Thriving floodplain habitats are fantastic freshwater habitats that provide many ecosystem services, such as carbon storage, water storage, sediment trapping, and habitats for many species. Floodplain grasslands can be very species-rich, with up to 43 plants per m2 (Wallace and Prosser 2015) and support special species such as Snakeshead Fritillary (Fritillaria meleagris) and Narrow-leaved Water-dropwort (Oenanthe silaifolia). By carrying out floodplain restoration using green hay we hope to see the return of characteristic floodplain grassland plants come back, including Common Knapweed (Centuraea nigra), Great Burnet (Sanguisorba officinalis), Meadow Vetchling (Lathyrus pratensis), and many more.
How will you know if it’s been successful?
The main indicators of success that you can look for are changes in botanical diversity before and after green hay spreading. Comparisons in species richness (number of species) and species diversity (relative numbers of species in each area) are good quantitative ways to track success.
We can also see if there have been any species composition changes by recording species lists and determining if there are now species establishing that weren’t at the site before. Monitoring of the plant species takes place each year in spring or summer, so success is hard to see until this point. Even then, some grassland species could take a few years to establish, and proper management is required to promote this. Over time it will become clearer if the process has been successful or whether further actions are required.
How and when can people visit a floodplain meadow/grassland site? Can people visit the site you used the Green Hay seed on?
One of the best times to visit floodplain meadows is when they are flowering from mid to late April-September. Hay meadows will mostly all be cut around June-July time, so heading to them before this time gives you the best chance of seeing them in full bloom. There are many floodplain meadows around Oxfordshire and some of the best examples are found within the Oxford Meadows Special Area of Conservation around the NW of Oxford, including several nature reserves.
For information on floodplain sites around the UK, the Floodplain Meadows Partnership have great resources on their website, including this map: https://floodplainmeadows.org.uk/discover/floodplain-sites-map
This work is part of the Oxfordshire-Buckinghamshire Freshwater Network project.
We are proud that this work is part of the Nature Returns programme led by Natural England in close partnership with the Environment Agency, Forestry Commission and RBG Kew, Wakehurst. Nature Returns is bringing together scientists, communities and investors to demonstrate how nature recovery leads to tangible returns in the form of carbon sequestration and increased biodiversity. This Shared Outcomes Funded Programme is sponsored. Nature Returns is a Shared Outcomes Fund Programme sponsored by by Defra and DESNZ.