Countryfile forgot the earthworms!

06/12/2016

On the BBC Countryfile programme broadcast on Sunday 4th December there was an interesting piece on the damage being caused to our rivers by modern agricultural operations. The programme highlighted soil run-off  into watercourses in heavy rainfall and the excessive nutrients, organic matter and toxic chemicals that can be bound up with it.

Importantly, the programme also touched on how farmers could have an important part to play in the solutions, and we were disappointed that these were limited and somewhat outdated.

One of the glaring omissions in the programme was the failure to show the state of some of our best known rivers, some of which are world famous for the quality of the water, their insect life and abundant fish populations.

Although the feature explained how populations of several wild fish species, especially salmon, had plummeted over recent years, it would have been much better if the BBC had shown footage of the result of agricultural diffuse pollution.

Firstly, let’s see what how a healthy chalkstream should look like

Upper River Test – clean gravels ideal for trout to spawn, and healthy weed growth

But, you don’t have to go far down the Test for the picture to be very different:


The Test photographed on the same day as the above.  Water clarity is poor and the bed is covered in algae – a sure sign of too much nutrient in the water, almost certainly from agricultural run-off

The Countryfile programme correctly talked about sediment from agricultural soil run-off clogging up river gravels and suffocating fish eggs that have been laid there. This is especially the case where sediment contains organic material, which sucks oxygen out of the water and leads to even faster egg mortality.

But there are other issues connected to excessive sediment and nutrient, especially too much phosphorous in the water.  Aquatic insects also lay their eggs in water, and research supported by S&TC UK has recently found out that the weight of sediment building up on insect eggs both dislodges them away from anchor points and suffocates them in a combined effect. This either makes them more accessible to predation or, if the predators miss them, then they are very likely to be swept down the river and out into saltwater, where they will die. If you add phosphorous to the mix, then fungus grows on the eggs, suffocating them and also entering the eggs to cause cell disruption.

So, sediment and nutrients not only impact fish eggs and thus fish populations directly, but they also destroy the food chain on which fish, birds and indeed mammals further up the chain depend. Shockingly, this can impact on the whole aquatic ecosystem.

Encouragingly, the Countryfile piece showed how farmers are helping by planting riparian buffer strips to act as filters for soil run-off and to keep livestock from entering watercourses to drink and so add to the sediment problem.

However, the programme failed to show some of the most up to date ideas that not only protect rivers but also add significantly to farmers’ profit margins. The answer is in proper soil management:

A freestone river in the Midlands, heavily impacted by sediment.  Very few fish eggs would survive to hatch in these gravels

There are other issues connected to excessive sediment and nutrient, especially too much phosphorous in the water.  Aquatic insects also lay their eggs in water, and research supported by S&TC UK has recently found out that the weight of sediment building up on insect eggs drags them away from anchor points and either makes them more accessible to predation or, if the predators miss them, then they are very likely to be swept down the river and out into saltwater, where they will die.  If you add phosphorous to the mix, then fungus grows on the eggs and kills them directly.  So, sediment and nutrient not only impact fish eggs and so fish populations directly, but they also destroy the food chain on which fish, birds and indeed mammals further up the chain depend.  The whole aquatic ecosystem is affected.

Countryfile showed how farmers are helping by planting riparian buffer strips to act as filters for soil run-off and to keep livestock from entering watercourses to drink and so add to the sediment problem.  However, the programme failed to show some of the most up to date ideas that not only protect rivers but also add significantly to farmers’ profit margins.  The answer is in proper soil management:

Inspecting soil from a zero-tillage field where earthworms have been allowed to aerate the soil, pull down organic material into the ground and increase water retention

Minimum and zero tillage of soil is an excellent way of overcoming compaction through the use of lighter agricultural equipment, which encourages the grown of earthworm populations, which naturally aerate the soil and pull down organic material from the surface. The holes they make also allow greater water retention in the field rather than the traditional heavy run-off from compacted soils, and the crop finds it easier to take up water. In time, crop yields are consistently higher than in ploughed systems.

The farmer therefore benefits from bigger harvests and reduced fuel and fertiliser costs and capital investment in equipment is also reduced, as smaller, lighter tractors, and drills replace the massive, fuel-guzzling hardware we are used to seeing in fields today.

S&TC UK is continuing to monitor rivers in England and Wales through our National Riverfly Census to record their ecological health by analysing insect life down to species level. Different species have different tolerances to sediment, nutrient enrichment, organic material and low water flows, and so the presence or absence of particular insect species is an accurate natural indicator to the quality of water and habitat in a given river reach.

From our experience to date, farmers want to be part of the solution to clean up our rivers and streams.  We just need Countryfile to catch up with these latest advances too.


A professional biologist prepares to take an aquatic insect sample from an English freestone river, much to the interest of cattle whose access to the river has been recently barred.  Already the riverbank in front of them is beginning to recover and be bound together with vegetation, saving further sediment and organic matter from leaching into the stream.