The ditch is back!

This blog post was written by Dr Vanessa Cutts, Research Associate, University of Cambridge, UK and Dr Helen Driver, Programme Manager at the Centre for Landscape Regeneration, University of Cambridge, UK

The Cambridgeshire Fens are home to a vast network of ditches that run along field edges and cut through lowland agricultural peatlands. They were designed originally with one purpose in mind: to drain water from the land so it could be farmed. But it turns out that ditches are much more than just drains. In intensively farmed environments, where many natural habitats have been lost, ditches can support lots of wildlife, including aquatic plants, insects, amphibians and birds. Ditches have been described as “the hedgerows of the Fens”, because they function similarly to traditional farmland hedgerows by providing refuge and acting as ecological corridors. Not only are ditches important for wildlife, but they also play important roles in intercepting pollution and influencing how water, nutrients, and even carbon move through a farming landscape (Clifford et al. 2025).

In the UK, the total length of ditches has been estimated to be longer than that of rivers and streams combined (Brown et al. 2006). There is growing recognition of their value and an increasing need to understand how they can be managed to support biodiversity and water management while still supporting productive farming. 

As part of the Lowland Agricultural Peat Water Discovery Pilot project (LAPDWP) led by Fenland SOIL, with the Centre for Landscape Regeneration we collated the global evidence on the effectiveness of ditch management on biodiversity. In just three months, we pulled together the evidence from existing Conservation Evidence synopses (any study that specifically looked at ditches), along with additional studies from our database. We identified 96 studies covering 48 different management actions, with evidence available for 35 of them. Most studies came from Europe, particularly the Netherlands and the UK, reflecting the long history of managed drainage systems in these countries. The studies assessed impacts across species, including plants, invertebrates, amphibians and birds. This is now published on the Conservation Evidence website.

What does the evidence say about ditch management?

There are some relatively simple actions that can enhance biodiversity with fewer apparent downsides, such as reducing pesticide inputs, creating buffer strips, or adding structural features like escape routes for wildlife.

One of the clearest patterns is that disturbance, such as ditch cleaning, is not inherently negative. While it often reduces plant cover and invertebrate diversity in the short term, many communities recover within a few years. Some species, particularly amphibians, may even benefit from the open, early successional conditions created. However, the frequency and timing of management matters. For example, ditch cleaning can influence amphibian and invertebrate development depending on the time of year it is carried out. One study found that ditches cleaned between July–September had higher presence of amphibian larvae than ditches cleaned in September–October, whereas the opposite was true for caddis fly larvae (Twisk et al. 2000).

There are also some relatively simple actions that can enhance biodiversity with fewer apparent downsides, such as reducing pesticide inputs, creating buffer strips, or adding structural features like escape routes for wildlife. In contrast, invasive species management tends to be less straightforward, with most control methods providing only temporary or partial success.

Agri-environment schemes: helpful, but not enough

The evidence suggests that agri-environment schemes can improve ditch condition and benefit some species, particularly amphibians, but their overall effectiveness for biodiversity is inconsistent (based on evidence mainly from the UK and the Netherlands). Outcomes vary widely depending on the specific actions implemented and the surrounding landscape, and schemes alone often fall short of delivering the levels of biodiversity seen in less intensively managed or protected sites. Importantly, some actions supported by agri-environment schemes, such as reducing management intensity or chemical inputs, are backed by evidence. But studies that directly test agri-environment schemes (by comparing farms in schemes with those outside them) show mixed results, and often fail to describe the specific actions being implemented.

Where are the gaps?

Many commonly used interventions are supported by only a handful of studies, and long-term outcomes are rarely assessed. As a result, there is still a fair bit of uncertainty about what works best.

One notable gap in the evidence base is the effect of ditch reprofiling. Shallow, wider ditches are often assumed to be better for biodiversity, as they can support more marginal vegetation and create a greater range of habitats (Buisson et al. 2008). While this makes sense in theory, we found surprisingly little direct evidence testing the impact of reprofiling on biodiversity outcomes. This highlights a clear opportunity for research. A forthcoming report by Friday et al. (2026) attempts to address this gap by examining how modifying ditch form and structure may benefit biodiversity, while maintaining hydrological function.

We found surprisingly little direct evidence testing the impact of reprofiling on biodiversity outcomes. This highlights a clear opportunity for research.

So where next?

There is a clear need for more targeted research to understand why some actions fail to deliver expected benefits, and how agri-environment schemes can be better designed for lowland peat landscapes like the Fens. Ditches take up relatively little space, but collectively they form vast networks across agricultural land. There is a huge potential opportunity to manage ditches effectively to support nature while meeting agricultural demands.

References

Brown C.D. et al. (2006) Morphological and physico-chemical properties of British aquatic habitats potentially exposed to pesticides. Agriculture Ecosystems & Environment, 113, 307–19. https://doi.org/10.1016/j.agee.2005.10.015 

Buisson R.S.K. et al. (2008) The Drainage Channel Biodiversity Manual: Integrating Wildlife and Flood Risk Management. Association of Drainage Authorities and Natural England, Peterborough.

Clifford C. et al. (2025) Lines in the landscape. Communications Earth & Environment, 6, 693. https://doi.org/10.1038/s43247-025-02699-y 

Cutts V. et al. (2026) Global Evidence for the Effects of Conservation Actions to Manage Ditches for Biodiversity. University of Cambridge and Fenland SOIL, UK. https://doi.org/10.52201/CESR/GCYQ4244 

Friday L. et al. (2026) Restoring Wetland Biodiversity: Balancing Synergies and Trade-offs in Multifunctional Ditches [in prep].

Twisk W. et al. (2000) Effects of ditch management on caddisfly, dragonfly and amphibian larvae in intensively farmed peat areas. Aquatic Ecology, 34, 397–411. https://doi.org/10.1023/A:1011430831180   

This work was carried out as part of the Lowland Agricultural Peat Water Discovery Pilot project, funded by the Environment Agency and Defra, led by Fenland SOIL in partnership with the Centre for Landscape Regeneration. This project was also supported UKRI NERC through their support for the Centre for Landscape Regeneration [grant number NE/W00495X/1].