There are 500,000km of ditches in the British countryside, reaching almost every corner of the land.

Found in most parts of the lowlands and surprisingly far up in the hills, ditches are open channels that run along the boundaries of fields, usually narrower than 5m wide and more than 20 times longer than their width.

Created by people, mainly to drain the land and remove excess water – with the right management approach they can also become a valuable habitat, supporting wetland plants and insects, such as water beetles, dragonflies and hoverflies.

See also: Why managing winter rainfall on arable land matters

Where larger, wider ditches are found in the landscape, especially if they have a shallow gradient, food and habitat for wading birds, amphibians and small mammals are provided.

Water corridors

While they aren’t considered to be priority habitat, ditches provide useful connection across landscapes while generating different habitats based on geographical aspect and prevalence of sun.

What lives in a ditch depends on how polluted it is, as well as its gradient and how often it flows, says the Freshwater Habitats Trust, which points out that the greatest benefit to wildlife comes from a ditch that is wet for most of the year.

© Tim Scrivener

Most importantly, it stresses, ditches are essential watery corridors across arable landscapes for wildlife and are often the only wet habitat around.

Given their value for wildlife and the contribution they can make to delivering biodiversity, how can that be maximised by farmers without risking field productivity and economic returns?

Diversity of habitat

According to Philip Bruss of the Berkshire Buckinghamshire and Oxfordshire Wildlife Trust, the key for species abundance is diversity of habitat.

“A ditch with a complex cutting and draining cycle will provide a lot more habitat niches than a ditch annually dredged to aid drainage,” he says.

“Clearly, where ditches are functional and dealing with, there may be a limit to how much can be achieved.

“But ensuring you have sediment at various depths, partial vegetation cover and providing banks of varying gradients along the length of the ditch will ensure that colonist species have places in the ditch to persist year on year.”

Major ditch species

Aquatic invertebrates, such as dragonflies and diving beetles, benefit greatly from well managed ditches, especially those that don’t dry seasonally, continues Phil.

“The larval stage of these species require water,” he explains. “Each dragonfly species tends to be niche according to larval habitat, so some require more silt than others. That’s why substrate diversity in the ditch matters.”

He adds that many aquatic invertebrates disperse by flight as adults, so the “aerial buffet” they provide for certain bird species and for bats is important.

“Bats forage along linear features in the landscape, so where you have a ditch paired with a hedge, they are in heaven.”

Amphibians need both permanent and temporary water bodies, while newts are found in permanently wet linear ditches. Unlike toads, both frogs and newts are not wedded to the waters of their birth and will rapidly colonise new wet features.

“Persistent aquatic plants are needed by newts as egg laying sites, so plants within drainage ditches should be encouraged,” advises Phil.

If these are rigid and stick up out of the water, they also work as emergence sites for dragonflies, he notes. “They dry out their wings on these before their maiden flight.”

Good amphibian numbers may also encourage grass snakes and even otters to make use of the channels. Wider ditches are used by birds such as snipe, for probing the silt for invertebrates, as well as herons and egrets spearing the water for fish.

“Ditch systems that are well connected to rivers and streams can support good populations of fish, as well as performing a nursery role through the shelter from aquatic plants.”

He concludes by highlighting their value to water voles. “Riverbanks are heavily patrolled by their main predator, the American mink, so ditches allow voles to move away from these areas. They will even persist in stagnant ditches.

“Water voles benefit from steeper sides than other species, so that they can easily burrow in above the water line.”

Recognising a water vole

© Adobe Stock

Water voles are very shy and often confused with rats. Here’s how to spot one:

• Rounded, blunt face
• Brown furry tail, half the length of body
• Small hidden ears
• Furry paws
• Deep brown colour
• Dives when alarmed, making a distinctive “plop”

This article is the first in a new regular series called Making the Most of Nature, which looks at natural on-farm features and the contribution they make to wildlife and biodiversity. The series will also highlight any funding opportunities and sources of specialist advice.