Rewilding & Water: Our best solution to flooding & pollution?
“35,000 HA of farmland are flooded in Britain every 3 years, a figure expected to rise to 130,000 by 2080.”
Writing in the aftermath of Storm Babet (October 2023), a storm which broke the daily October rainfall record in 13 areas of Great Britain, flooded tens of thousands of acres of highly productive farmland, killed 7 people and destroyed 1000s of homes; we are already dealing with the ramping effects of climate change. Warmer air holds more water and with that comes more rainfall. Alongside making every effort to dramatically reduce greenhouse gas emissions, we need to build resilience to the effects of climate change. Even if we manage to hold climate warming to the 1.5C target outlined in the Paris Agreement, an outcome which is sadly looking increasingly unlikely, there is enough in-built warming in the system to cause a significant increase in extreme weather events, including more intense periods of rainfall (1). Unfortunately whilst the intensity and frequency of extreme weather events increases, we have simultaneously eroded our ecosystems’ ability to cope with these extremes. Focusing in on water; centuries of overgrazing our uplands, straightening our rivers, expanding the built environment, removing hedgerows, scrub and woodland and expelling keystone species have crippled our natural defences to flooding and drought.
‘In 2022 untreated sewage entered Britain’s water courses 389,000 times’
So what do we do?
In Great Britain we spend on average £2.2 billion a year on flooding, with £800 million spent on building flood defences and £1.4 billion in damages. In total its estimated that £200 billion of assets are at risk of flooding damage (2). Sadly the problem doesn’t stop at flooding. The quality of the water flooding our lowlands, rivers and coasts is also dangerous. Britain’s waterways are already critically polluted, with only 14% of our rivers deemed to be in good ecological health and in 2022 untreated sewage entered Britain’s water courses 389,000 times (3). This issue is heavily compounded by flooding events, when Britain’s antiquated sewage system mixes rain water and raw sewage in the same outflows, meaning that whenever it rains, the water companies have a legal exemption to let untreated sewage out with the rain water. Furthermore, the rain that lands in our heavily grazed or ploughed fields takes off valuable topsoil, as well as any other fertilisers, manure or pesticides, sloshing into our rivers before being dumped out to sea. This polluted water, filled with a concoction of sewage, chemicals and top soil provides the perfect storm for habitat destruction, both in our rivers and coastal areas, as well as a risk to human life. Of course, one solution to this problem is to update the sewage infrastructure. But with decades of underinvestment, the infrastructure transformation required is a huge undertaking costing billions of pounds over a multi-decade period (4). In the short to medium term, we need to dramatically reduce flooding events and limit the amount of pollutants reaching our water courses. But if we can’t stop the rain, how can we reduce the flow of water? Enter rewilding, a solution which simultaneously slows the flow of water and cleans our waterways, all for a much cheaper price tag than the £1bn we spend per year on flooding and erosion defences.
How can rewilding reduce flooding and clean our water?
Rewilding, particularly in upland areas, can dramatically slow the flow of water in areas downstream of the projects, reduce soil run-off and reduce pollution. This is achieved through 3 core tenants of rewilding:
Beaver introductions
River restorations (re-wiggling)
Increased vegetation.
Beaver introductions
The top pool of a beaver dam the Knepp Estate following an introduction 1 year prior. The pool is roughly 1 metre higher than second pool beyond. This was once a small stream and is now a wetland area, packed with vegetation and deep pooled areas. Water quality downstream has dramatically improved, flooding has decreased and numerous species, including brown trout, have returned in abundance.
Beavers are remarkable water management engineers. They are well renowned for their dam-building activities, which they use to deepen water ways and create the habitat necessary to build their lodges with under-water entrances, which are designed to keep land-based predators out. They have highly sensitive whiskers which can sense flows of water, meaning that they’re proficient at blocking holes in their dams. The advantage of these dams are that the still water creates habitat for fish, whilst the debris holds up sediments in the water, stopping top soil and pollutants from rushing out to sea., whilst also slowing the flow of the water. In a US study, water took three-to- four hours to travel 2.6km where there were no beaver dams. When a single leaky beaver dam, 1.5m high, was established, it took 11 days for water to cover the same distance (5). The University of Exeter found that beavers living on the river Otter in Devon had reduced the peak volume of water leaving the site by 30% and had trapped more than 100 tonnes of sediment in 7 years, 70% of which was soil which had eroded from 'intensively managed grassland' fields upstream. This sediment contained high concentrations of nitrogen and phosphorus, which are nutrients known to create problems for wildlife in rivers and streams and which also need to be removed from human water supplies to meet drinking-quality standards (6).
Eurasian beavers are native to the UK and would have once populated almost every river across our Isles. Hunted to extinction in the 16th century, our water courses are sorely missing these incredible engineers. Fortunately beaver populations are now on the rise in the UK and have recently received protected status. Although some progress has been made, we are still dramatically behind our European neighbours in beaver numbers and regulatory barriers still require beaver releases to be held in fenced enclosures. Beaver reintroductions are a cheap and highly effective solution to the flooding, drought, water pollution and biodiversity crises we face, and one which we should be rolling out rapidly and at scale. Resistance to this solution comes from a few quarters, some of which are totally unfounded, for example the belief that beavers eat fish stocks (beavers are herbivores and their engineering work boosts fish populations). Other resistance comes from landowners who are understandably concerned that beavers’ activity will alter the course of streams or rivers running through their land and take some riparian areas out of production. This is a more legitimate concern, and one that needs to be addressed with policies which would financially remunerate land managers who allow beavers on their rivers for the ecological services they provide, as well as support to relocate un-wanted beavers. This could be allocated through the new Environmental Land Management Scheme (ELMs) which pays land managers public money for public goods. The NFU and other outspoken critics of beaver introductions also reference food sovereignty, arguing that beavers would flood certain fields around rivers where beavers are introduced. This argument fails to take into account that we currently lose 35,000 HA of highly productive agricultural land to flooding every 3 years, a figure which is expected to rise to 130,000 HA by 2080 (7). By allowing beavers back into our water courses, we will lose some farmland directly around our rivers and particularly in less productive upland areas, but we could dramatically reduce the impact of flooding downstream on farmland and urban areas. In England, about 20% of our farms produce 80% of our food and a little under half (42%) of England’s farms produce a meagre 2% of the total agricultural output. Dedicating some of that 42% to clean our water and reduce flooding in more productive areas make sense from a food & water security perspective (8). Another criticism of beavers is that they can reduce tree numbers on river banks. This is true as beavers do fell trees on river banks to create their dams, but when beavers fell trees, the tree often survives in a coppiced form. Indeed riparian trees like willow thrive from coppicing, and a felled tree ‘creates nest spaces for birds, refugia for many invertebrates and even creates dappled shade which fish like trout and salmon thrive in (9).’ Lastly, we can easily protect certain trees from the iron-clad beaver teeth with taste repellants, grit or wire mesh. In summary, given the scale of the flooding, water quality issues & food security issues that we face, it's an absolute no-brainer to scale out beaver introductions as rapidly as possible across the UK.
River Restoration
1 of 129 large timber dams upstream of Pickering, Yorkshire.
River restoration goes hand in hand with beaver introductions, and indeed the cheapest way to restore a river is to introduce beavers. However, where this isn’t feasible or perhaps in conjunction with the introduction, humans can intervene in several ways to improve the health of our water courses and reduce flooding. The most popular ways of doing this are either by creating leaky dams along the upland course of the river, mimicking beaver activity, or by re-wiggling the course of the river with a digger, creating lower banks and connecting the river to a floodplain. Several of these nature-friendly solutions were implemented to great success near Pickering, Yorkshire, after a particularly bad years of flooding in 2007 and 2015. Instead of building a larger and highly expensive flood wall, the community decided to take a different path, implementing 167 leaky dams in the upland rivers, planting trees in the uplands and creating a planned floodplain, all of which reduced the risk of flooding from 25% in any given year to 4%. (10)
Increased vegetation
Another reason we are feeling the effects of flooding so badly in Great Britain is because our uplands are largely devoid of vegetation and trees. Over centuries we have cut back trees and over-grazed our uplands, ensuring that they are featureless & largely lifeless. Instead of having robust complex ecosystems rich with vegetation which would absorb rainfall, we have compacted soils which send rainwater downhill immediately. Rewilding these uplands and, where necessary, planting trees can dramatically increase the land's capacity to absorb and slow down the flow of water. The effect that trees have on vegetation has been conclusively proven in the Pontbren Project in Wales, where a collective of farmers noticed that water run-off from their grazed fields disappeared when it reached the edges of woodlands. From this observation, they decided to plant bands of trees on their upland fields. The project found that the ground around trees absorb water at 60 times the rate of open pasture land. In fact, ‘The data on water movement showed that in grasslands grazed by sheep the overland water flow can be a more important runoff pathway than the field drains (11).’ In other words, the impacted, over-grazed soils were more effective at pushing water downhill than drains designed to do just that. As an added bonus, vegetation helps to purify water as well as slow its flow, meaning that we get cleaner water slowly being released during periods of flooding and drought. Grazed uplands hold significant cultural value for many communities, not to mention a livelihood for many farmers, but this doesn’t mean we can ignore the fact that upland grazing negatively impacts flooding, drought & biodiversity. Instead we need a mixed approach, embracing more wooded pastures and financially incentivising farmers to plant more trees in their upland fields, or to rewild tracts of land upstream of flood-risk areas.
In conclusion, to solve the mounting issues of flooding and water pollution, we are faced with a ‘choice’. We either double down on vastly expensive and ineffectual concrete flood defences, which force polluted water onto our farmlands and eventually out to sea, whilst leaving our depleted rivers in an ecologically barren state. Or we embrace nature based solutions in our uplands, which alleviates the problem at its source, boosting biodiversity, protecting our soils and reducing flooding, all at a fraction of the cost of carbon-intensive cement defences. Building bigger walls to ring-fence our towns whilst disregarding the root of the problem, is an act of wilful ignorance and akin to shoving the problem under the carpet. After decades of cautious trials, the course of action is now evidently clear, we just need to get on with it.
(1) https://www.npr.org/2021/11/08/1052198840/1-5-degrees-warming-climate-change
(2) https://assets.publishing.service.gov.uk/media/5a74c78de5274a3f93b48beb/04-947-flooding-summary.pdf
(3) https://www.sas.org.uk/water-quality/water-quality-facts-and-figures/
(4) https://www.gov.uk/government/news/largest-overhaul-of-sewer-system-to-tackle-storm-sewage-discharges
(5) The Beaver: Natural History of a Wetlands Engineer, Müller-Schwarze, D., and L. Sun. 2003
(6) https://www.sciencedaily.com/releases/2018/05/180509121552.htm
(7) https://eciu.net/analysis/briefings/climate-impacts/flood-risk-and-the-uk
(8) https://gca.org/let-half-of-britains-farmland-go-wild-and-it-benefits-us-all/
(9) https://treecouncil.org.uk/why-do-beavers-matter-for-trees-in-conversation-with-beaver-trust/
(10) https://environmentagency.blog.gov.uk/2015/11/11/slowing-the-flow-working-with-nature-to-reduce-flood-risk-in-north-yorkshire/
(11) https://www.woodlandtrust.org.uk/media/4808/pontbren-project-sustainable-uplands-management.pdf