Floods in York and the North of England made the headlines over this Christmas break, when many lives were threatened and local households and businesses suffered an estimated £1.3 billion of damage . The University of York was not directly affected and we hope that all York students were safe and nothing but witnesses to this event!
Speculation and investigations into the origin of this serious incident and questions as to who should be held responsible have been raised promptly by the national media. Ill-design of the city’s flood protection barriers, mismanagement of water-streams and farmland, irresponsible decision-making and subsidy allocation, and ultimately climate change, have all been mentioned as critical contributors to the making of this tragedy.
One of the potential causes of flooding is degradation of habitats which could otherwise hold back large quantities of water. In this blog article, we wanted to take the chance to discuss how bogs perform this function and why some bogs are not in a state to do this effectively, a subject that is currently being investigated at the University of York by Phoebe Morton, a PhD student based at the Stockholm Environment Institute’s York branch (SEI-Y).
I recently had the opportunity to join her and the team on a three-day field trip taking environmental measurements over a number of locations on moorlands in Northern England. As a chemist, I am used to experiments being carried out in a very confined, conditioned, and reassuringly neat environment, only a few steps away from my computer and a warm cup of tea! The experience of volunteering on this project was an eye-opener into the world of outdoors data collection and environmental experiment design.
Each site we visited was a grouse farmland that at the time of our visit in August was beautifully covered in purple heather, the main source of food for the grouse. As pointed out in a recent article in The Guardian , this land that is very profitably dedicated to grouse hunting is often managed with little regard to the long-term sustainability of its supporting ecosystem, which comes at the expenses not only of the environmental value of these lands – e.g. for carbon fixation, emissions retention, soil structuring, biodiversity preservation – but also of the safety of the human settlements downstream, as we seen in York.
In those three days, I gained a direct insight into the issues and consequences of various moorland management strategies, and witnessed with my own eyes the difficulties underlying both the impact assessment as well as the development of an ultimate solution to the problem. Phoebe has shared some more details about her project with us, keep reading below to find out more!
As Giulia has pointed out, all three sites are managed as grouse moors. However, all are (or were depending on your definition) bogs. A bog is an area of wetland which has an underlying soil of peat and is usually covered in a carpet of Sphagnum mosses. Peat is excellent carbon store because the wet conditions slow decomposition down to the point where peat depth can increase up to 1 cm in 5 years (that’s incredibly quick for soils and represents about 4 kg of carbon per square metre!). The bogs are so wet because Sphagnum mosses have large spaces in between their cells which can fill with and retain water. As the peat is composed largely of semi-decomposed Sphagnum, it also has the ability to hold vast quantities of water which drain very slowly.
Whilst it may be in many people’s interests – and indeed the world’s – to manage bogs for maximum carbon storage and minimum water release, grouse moors are managed for grouse. Landowners and gamekeepers (and often the local rural economy) want to manage the land for maximum grouse numbers in order to provide a surplus for shooting.
Naturally this creates a conflict of interest: in order to maintain an actively growing bog, Sphagnum needs to be present at in high quantities, to retain moisture and form the peat. Cotton-grasses are required to aid peat formation and prevent soil erosion but instead moorland managers demand vast swathes of heather (Calluna vulgaris), the predominant food source for red grouse (Lagopus lagopus scoticus).
Whilst the project on which I work is not directly investigating flood risk, it could impact indirectly on flood mitigation. We are investigating the effects of different types of heather management on bogs managed as grouse moors. The typical management is to burn areas of heather by rotation over 10 to 20 years to encourage new shoots of heather for the grouse to feed on. The burning also dries the peat and can destroy Sphagnum plants. We are looking predominantly at whether mowing the heather is as detrimental to the bog ecosystem as burning. The hope is that the peat will remain wetter, will retain more carbon (we measure both carbon dioxide and methane fluxes), there will be more Sphagnum, and less water runoff during heavy rain. Currently the results look encouraging although the project is ongoing.
As well as being able to retain water and release it more slowly, hopefully reducing flood risks without the need of large concrete barriers, the peat in fully functioning bogs filters and cleans the water as it trickles through. Few people are aware that about 75% of the UK’s drinking water is filtered through peat before it even reaches a water purification plant. If the peat the water runs through is in good condition, it is likely the water companies will have to treat it with fewer chemicals before we can drink it. This is beneficial for us, both for our health and the price of drinking water!
Contributed by Giulia Paggiola and Phoebe Morton
Giulia is Founder of the greenSTEMS group and is currently pursuing a Ph.D. degree at the Green Chemistry Centre of Excellence. In her research she collaborates with Stockholm Environment Institute at York and with European pharmaceutical industries urging the adoption of renewable and safer solvents in drug manufacture.
Phoebe is a PhD student at SEI York, working with Andreas Heinemeyer on a Defra project on peatland management and ecosystem services in the UK. She is specifically looking at the effects of different types of heather management on peatland vegetation, carbon dynamics, greenhouse gas fluxes and water quality.
Phoebe has a BSc in Biology (with a Year in Industry) from the University of York. Her undergraduate project focussed on investigating how mycorrhizas and biochar (charcoal) affect greenhouse gas fluxes from forest soil. She worked for the Game & Wildlife Conservation Trust in the Scottish Highlands for a year as a placement student, which included work with gamebirds in a wide variety of upland habitats, assessing vegetation changes and habitat mapping.