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Dunes and dung beetles. Is all poo good poo?
Dung beetles have developed a range of ways to utilize what others leave behind. Some shape the stuff into balls even larger than themselves and roll it away to use later, some dig tunnels and proceed bury their faecal findings, some set to work stealing another’s hard-collected dung, and some actually opt to set up house within it. For the 60 or so dung beetles in the UK [1] the discarded waste of mammals like cows, rabbits, deer, ponies and sheep can be both a meal ticket, a maternity ward and an entire home.
These beetles are completely dependent on animal dung, that’s a given. But what is increasingly becoming understood is that we are actually quite dependent on them. Unknowingly, perhaps, they bring with them myriad ecosystem services and do life in the surrounding habitat a whole host of favours. These little black (mostly) beetles are fantastic recyclers and nutrient distributors; the farming industry has used dung to improve yields for centuries, but these invertebrates are the original muck-spreaders.
However, recent decades have seen a mass exodus of our slurry-slingers; population numbers are down and 25% of dung beetles in the UK are classified as ‘nationally rare’. [2] They’re another chapter of a story we all recognise. Dung beetles, as with most insects, are persistently threatened by human activities which lead to loss of, or the degradation of, suitable habitat. [2]
In a sand dune, unchecked vegetation succession that sees grasslands succumbing to the advances of stubborn scrub can impact dung beetle populations – as well as many other sand dune specialists. So too can the use of pesticides or the use of herbicides to control vegetation growth. The reintroduction of grazing animals such as cattle or ponies then, has clear benefits for dune-dwelling dung eaters. Not only do grazing livestock maintain short grassland and prevent rapid scrubbing over in a natural way without the use of unwelcome chemicals, heavy machinery reliant on fossil fuels, or the cost associated with land management contracts, they also, er, poo.
To boil it down, the excess organic matter is browsed and provides sustenance for these hardworking herbivores, before whatever manages to reach the end of the digestive tract journey is served up for invertebrates. They’ll have their fill of the remaining nutrients before helping the solid stuff return to the soil, where it can improve soil health and nutrient levels, introduce a variety of useful microbes and, possibly, store a little bit of carbon.
These busy beetles speed up the process of turning manure into things that other organisms can use. [3] Without them, ecosystem microorganism composition and diversity could reduce, the soil structure and health itself could decrease, and faeces deposits would remain atop the surface of the ground, waiting for weathering to help its nutrients return to the soil. [4]
It’s quite a satisfying loop. A natural circular economy; provided grazing cattle aren’t fed with supplementary food coming from outside the ecosystem, all resources are used multiple times and there’s no waste. Historically our countryside – dunes and coastal heathlands included – would have been grazed by wild, free-roaming grazers like hardy breeds of pony, cattle and pig. And in those times, no doubt, dung beetles would have dined like kings.
In the dune heath at Studland Bay, where Dynamic Dunescapes has funded the reintroduction of grazing cattle to manage over-vegetation, the cattle’s Grazier and National Trust Rangers will often flip over a fresh ‘pat. Sometimes holes where the beetles have scooped out the building materials for roll-able dung balls are clear, and sometimes the beetles themselves are spotted.
It's a curious conversation, though; dung and sand dunes. There is a faecal hierarchy. By all means, not all poo is good poo. Ultimately, our dune habitats in the UK are suffering from too much nutritional input – lack of grazing has led to increased plant growth followed by a build-up of organic matter, humus and soil, resulting in yet more plant growth. Excessive plant growth reduces habitat quality for dune-specialist wildlife and, in turn, decreases dune biodiversity – something which makes the habitat less resilient to the impacts of climate change. Unlike cattle which eat and live on the dunes, the dung deposits of visiting dogs increase the nutrient content of the ecosystem by bringing said nutrients in from elsewhere, and so conservationists would prefer that when it comes to four-legged recreational dune visitors, poo bags are used and dog poo taken home or put in a bin.
Dung and the beetles that work hard to recycle it are a vital part of our ecosystems, but for some forms of poo, it seems, there is a time and place. To help restore our damaged coastal ecosystems the dung beetles in our dunes, like us, should be eating seasonally and locally, rather than dining out on imported goods from lands further afield.