Are sponge soils the key to future UK climate resilience?

Energy & Climate Change, Flooding, Natural Environment, Water Resources

Awareness of the flood risk management benefit of improved soil management is spreading fast. But as the UK bounces from arguably its most familiar climate-water challenge to drought, should we be thinking far more about healthy soil’s water resources benefits? They could be substantial writes Alastair Chisholm.

At the Flood & Coast 2022 conference recently the then Environment Minister was extolling the virtues of ‘sponge cities’: Blue-green infrastructure woven into the urban fabric to soak up surface water and mitigate flash flooding risk.

Earlier in the year I was lucky to be invited on a trip around the upper Aire catchment above Leeds to view the natural flood management (NFM) components of the Leeds Flood Alleviation Scheme phase 2.

Alongside the truly impressive scale of tree planting the aspect those involved seemed to wax lyrical most about was soil aeration.

This was reversing the decades-long combined effect of millions of tiny sheep hooves and tractor tyres compacting the soil, dramatically improving its infiltration and water storage capacity. Results are speedy and cost-effective as equipment can be shared amongst neighbouring farmers.

Water stress and drought

‘Slowing the flow’ is now part of the flood risk management lexicon, but not so much when it comes to farmers in crisis or hosepipe bans.

Conversations with a couple of farmers from East Anglia highlight that they’re staring down the barrel of a soil moisture deficit gun. “Things are absolutely dire” they say. NFU President Minette Batters echoed this concern by saying we need a “radical rethink” about how water resources are maintained.

Meanwhile, the regional water resources groups have been setting out their emerging regional plans, looking across their areas for the best combinations of schemes and measures for their member water companies to implement in forthcoming water resources management plans.

The regional groups consider resilience issues to public water supply (PWS), alongside other non-PWS uses such as agriculture and energy. Eye-watering sums will need to be spent to ensure reliable drinking water supplies alongside the needs of other water-using sectors and at the same time making sure there’s still enough water in rivers for nature.

And the challenge becomes incredibly problematic under the less-optimistic climate scenarios they consider.

In Southern England, water availability (or lack of it) is preventing development from taking place. Last year Horsham District Council was told by Natural England that abstraction was negatively impacting protected sites and any future development in its local plan would have to ensure that no further water was taken from the environment. In other words, it should be water neutral.

We’ve witnessed the rapid spread of nutrient neutrality restrictions on development. It’s far from unlikely that similar could happen in many other water-stressed parts of the country.

A range of solutions to this water supply challenge are being considered, from reservoirs and transfers to reducing mains leakage, and household-level water efficiency. In the context of a balanced approach, that is all appropriate.


But what do all these things have in common? The role of soil as a means of infiltrating and storing water could very likely make a tangible and very cost-effective contribution to the various pressures that are ramping up at either end of the water quantity management spectrum.

Consider this: About 37% of the storage capacity for water in the UK is currently held in our soils. Whilst the place many might consider to be the main storage capacity would be water bodies (lakes and rivers), that’s a small proportion compared to soils and the vegetative canopy because soils and canopies are everywhere and water bodies are not.

So, there are two questions worth pondering:

  • If soils were widely managed in a way which considered and optimised their water-infiltration and water-holding capacity, how much might that reduce some of the pressures being put on water resources by PWS, new development, agricultural irrigation and the like?
  • If soils currently store 37%, how much could that enhance the recharge of groundwater and aquifers, which feed rivers and keep our water environment in a healthy state?

The answers are almost certainly unknown, but research[i] is being done by Kings College London into the effectiveness of sustainable land management techniques, such as regenerative farming, within a basket of different NFM measures. And it’s showing eye-catching numbers at the landscape scale.

Regenerative farming

The principles of regenerative agriculture focus on minimal tillage and increased plant cover and diversity. These factors improve soil organic matter and structure, enhancing infiltration and slowing runoff – well-recognised as a principle if not yet extensively quantified in detail.

Reduced bare soil area mitigates moisture loss during drought. This is aside from the additional soil fertility, biodiversity and carbon sequestration benefits that improved soil management can achieve.

An approach that is progressively gaining recognition, regenerative agriculture nevertheless requires a brave (and potentially expensive) step to be taken by farmers to transition from more conventional intensive approaches.

For those who successfully make the transition, productivity levels can be comparable to these intensive methods and require far less inputs in terms of fertilisers and pesticides.

Regenerative agriculture advocates point to the potential – in a climate increasingly (in the South and East of the UK at least) moving towards semi-arid with seasonal rainfall – for farmers to take advantage of these conditions to even increase yields through regenerative approaches. Rather than this climate being a threat, with the right approaches to managing water they could present agricultural opportunity.

However, that transition – which can last a handful of years – often involves an initial productivity drop which could be prohibitive for many farms operating at the margin. Then again, capital investment in on-farm water storage, plus dramatically increasing annual fertiliser prices present increasing barriers to conventional farming. Grants are available to support farmers for water-related capital investment, but not currently to make the transition to regenerative approaches.

Runoff or infiltration?

Run-off of water from land has become a dominant feature of the UK landscape as agricultural soil has become compacted and denuded of organic matter.

But in the majority of cases, for well-managed land and healthy soil, runoff needn’t occur. Experience indicates that areas of standing water are very commonly actually indicative of dry soils not far below – because that water will only infiltrate the first 2cm or so at a snail’s pace.

Side-by-side testing by Kings College of conventionally and regeneratively farmed fields point to far higher water storage capacity under regenerative management, and the UK-typical 86ha farm potentially being able to store an additional 67,000m3 of water – or 67 megalitres over a week of monitoring.

With 192,000 farms in the UK the potential begins to look significant even if a small fraction of these holdings were in valuable locations for resource recharge and embraced these kinds of approaches (a crude extrapolation for illustration only points at 12.8 million megalitres additional storage during that time period).

For comparison, Southern Water’s Bewl Water has a 31,000 megalitre capacity and daily production of most water treatment works is somewhere between 10 and 500 megalitres per day (ML/D).

The Government’s infrastructure advisers have recommended that by 2050 the UK will need another 4000 ML/D to cope with climate change and development pressures’ impact on water resources.

As a flood risk management measure, the Kings College research points towards regenerative agriculture being highly effective: For the same volume of flood storage, the most cost efficient method in all cases is regenerative agriculture.”

Of course the science of translating that storage and infiltration into groundwater recharge and buffering against drought effects needs to be understood in greater detail, but Affinity Water are working with farmers to protect water quality and resource and describe pores in soil as “the first pipes in our water system”.

Severn Trent Water also offers farmers a Regenerative Pathway Package but thus far, companies have focused on this from a water quality and nutrient management perspective rather than a resources one.

This may be because water company investments still tend to focus on physical assets that can be added to their balance sheets, rather than operational activities. This is something recognised in the consultation on the latest Water Industry Natural Environment Programme as a hurdle to maximising investment in nature-based solutions.

Soils for water in ELM?

The post-Brexit Environmental Land Management Scheme is being developed to deliver greater levels of beneficial public goods through the provision of public money to farmers and land managers. This is driven through its Sustainable Farming Incentive (SFI) and Local Nature Recovery programmes.

One of the underpinning means of achieving this delivery is the development of standards under the SFI. These set out how various aspects of the farm environment should be managed.

Standards include those for soils, with an expanding suite to cover various approaches for nature, and a working group has been set up to develop a standard for water. Soils standards consider issues relating to water quality, climate resilience and biodiversity. Defra states that “in future, standards will be designed to be compatible with each other”.

Now – in the spirit of shaping an agricultural support mechanism uniquely suited to the particular needs of Britain – must surely then be the time to conceive something more integrated and holistic. Something which considers water resources as a major area of need, particularly in the South and East of the Country?

How far might ELM soil management standards – compatible with those for water – encourage farmers to manage them for good water management on a whole-farm basis? And likewise, should a water standard look beyond the conventional buffer strip approach to protecting nearby watercourses and fully consider what lies beneath; its absorbency and retention?

Advice, monitoring and evaluation

An age-old challenge with driving good environmental practice through agricultural schemes was the provision of sufficient volume and accessibility of advice. Ensuring that standards developed under ELM hang together in a coherent way and achieve the best outcomes (public goods) will of course need that.

But unlike past schemes advice has to be about holistic management, rather than scheme compliance, or specific areas like biodiversity or diffuse pollution reduction, considered in siloes. Are Defra ready to support the industry through such a fundamental change? Current events should give a jolt to test that appetite.

Equally – and this has been a source of much teeth gnashing as ELM has developed – there will need to be a big increase in decent quality data collection and analysis. This is needed to underpin understanding of which actions that standards might point towards are actually effective in delivering outcomes (and the overall ambitions of the Government’s 25 Year Environment Plan), and which aren’t.

The future of ELM (and indeed our environment) will live or die on this data, but at present forward-thinking farmers say the appetite to collect and analyse it for the public good seems to be vanishing as fast as water in the South East.

Joined-up policy and funding

Fundamentally, actions such as soil aeration or regenerative agriculture can potentially deliver outcomes for both flood risk management and water resources, not to mention water quality.

These are almost completely independently-funded areas of water management which, with a well-monitored, outcomes-approach where benefits could be reliably quantified and delivered through a single action could be tapped into by land managers.

This could suddenly make water management a profitable business for farmers alongside food production: Integration of multiple public and private funding streams would support a higher overall valuation of these services, in-turn making the cost-benefit justification for data-gathering and monitoring of outcomes easier: A win-win.

If concerns over stacking payments can be overcome then farmers selling water storage services within their soils as a measurably profitable value-add to their core farm businesses could – maybe – happen.

'Stacking' should in principle operate as a process where an agreement will be struck with a buyer at a price for a specific outcome (e.g. flood resilience, or groundwater recharge, or biodiversity enhancement).

Buyers of these specific services would then pay less than they would if they had funded the whole on-farm action (e.g. going regenerative, or beaver introduction) themselves. Land managers meanwhile, achieve the higher price they need to take up more challenging but higher environmental value-add interventions.

It probably sounds outlandish now, but in the face of the climate pressures we face – both flooding and drought – we should be thinking this way and working fast to fully understand just what healthy soils can give us. Not just from a food security point of view, but also from a climate and water resilience perspective.

Soil – that long-abused medium which is on borrowed time with our current approach to managing it – could just end up being our saviour with a bit of sponge-treatment.

Alastair Chisholm
Director of Policy

[i] 2022 Mark Mulligan, Arnout van Soesbergen, Caitlin Douglas and Sophia Burke Natural Flood Management in the Thames Basin: building evidence for what will and will not work in Elena Lopez Gunn, Peter van der Keur, Nora Van Cauwenbergh, Philippe Le Coent and Raffaele Giordano (eds) in Greening Water Risks. Springer. In press.

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