Voice Of The Field: Rewilding flat fields with ant hills

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The second of our new content series, ‘Voice of the field,’ will showcase the collaborative work the Ecosulis team does on lateral thinking, focusing our collective minds on a range of environmental questions, problems and phenomena that impact our rewilding and conservation work. We enjoy inductive reasoning. This begins with observations and incidents and forms logical, generalised theories based on these.

It complements the deductive-hypothesis testing science conducted in our universities. For a more in-depth unpacking of our thinking on the inductive method, read chapter 4 of Dr Paul Jepson and Cain Blythe’s book Rewilding. Here though, we wanted to show how our current work and thinking on ant hills demonstrates the way inductive thinking works in practice.

Ecosulis got invited to provide some design input to an estate in southern England wanting to rewild heavily ‘smoothed’ agricultural fields. Our nature recovery lead Dr Paul Jepson began to think around the way a functional ecosystem ant hill could add structural complexity and ecospaces for specialist plants and animals.

He asked his team how they might kickstart the process of ant hill recovery. “We often start our biweekly meetings by throwing these rewilding challenges out to the team,” says Paul. “I’m keen to keep us grounded and encourage observation, enquiry and creative thinking.”

Ecosulis’ Nature Restoration Specialist Neil Melleney adds: “When badgers break into large ant hills looking for larvae, I’ve noticed the odd grass stem, but wasn’t sure whether these were an integral part of the structure.” He also notes that he has always marked out ant hills in meadows before mowing to avoid damaging and destroying them. “Paul’s question made me wonder how they get going in the first place.”

During a spring trip to The Isle of Purbeck, Paul was struck by the number of ant hills on the medieval strip lynchets on the walk from Worth Matravers to the coast. The lynchets are ancient sheep pasture and, prompted by Neil’s idea, Paul wondered whether the patches close to the dung promoted the growth of rough grasses on which ants built their nests.

Back home, and with these thoughts in mind, Paul noticed that rises of lockdown dog walking had led to patchiness (as a result of the hormones in female dog urine) in his local meadow. “I was interested in the impact of this, knowing that carnivores as well as herbivores have this ecosystem function. The urine of dogs is rich in nitrogen and other nutrients and, because multiple dogs tend to wee on the same patches, the result is a ‘nutrient dump’ in specific places.” Paul asked the team whether such dumps could be ant hill catalysts.

“I had Paul’s observations in the back of my mind when I was in a Berkshire meadow,” says Neil. “While walking through my local meadow, a well-established site sandwiched between an ancient woodland strip and cereal fields, I noticed soil around the base of juvenile ragwort. It appeared to have been placed there, one grain at a time and definitely by ants.”

Neil shared his observations with Paul and they wondered together about the combination of plants and ants, as these multi-layer interactions are key in restoring habitat functions. 

The following month, Neil was in a meadow, and his new awareness meant he quickly noticed another ragwort with soil. “Then I noticed others – including one covered to the tip with soil. Immediately I understood this made sense from an evolutionary point of view as ragwort is poisonous to livestock and rarely eaten fresh, so for ants, it was likely to be a safe base for their nest.”

Neil sat down in amongst these amazing structures to look more closely at what was going on. “I noticed the ants creating the soil camps were not the yellow meadow ant Lasius flavus, responsible for the mounds, who spend their time underground and interact with plant roots and root aphids, but black garden ant lasius niger. They build these nests whilst tending to the ragwort aphids Aphis jacobaese (which I discovered close by). Although initially disappointed I had not stumbled on a mechanism to kickstart yellow meadow ant mounds, I was intrigued and decided to look into it further.”

Although the black garden ant lasius niger is abundant, I saw other ant species like Lasius umbratus, whose queen acquires a “scent” camouflage and gets allowed into the lasius niger nest where her offspring are then tended by the lasius niger workers, until eventually the lasius niger colony are replaced by Lasius umbratus ants.

The same approach is used by Lasius fuliginosus, however, they hijack nests from Lasius umbratus who need to first to steal a lasius niger nest. As both these ant species can’t start their own nests, and are reliant on lasius niger, their presence in the landscape is essential, to ensure not just ant diversity but, to the many other species they in turn support.

“In the same meadow I also saw new yellow meadow ant mounds forming, and fear these will probably be flattened when the meadow has its end of season cut. In contrast, grazing animals would feed around these features, allowing them to remain in the landscape and grow year on year creating micro habitats and supporting further ant species transitions.

I also found there has been some work on the interaction between ragwort, livestock, ragwort aphids, ants and toxic alkaloid levels in the leaf. This is interesting because where ragwort aphids and ants are present, there tend to be lower levels of alkaloids recorded. I wonder if the chemical change is a temporary response to the aphid attack alone, or if this gets expressed in the seeds produced that year?”

When we ask ourselves a question about the natural world and start to look for answers, what we find is often more complex than we imagined. This brief glance at the interactions between meadow plants, ants, and the consequences of their nesting and feeding interactions shows why a focus on restoring habitat function, not single species, leads to the biggest biodiversity gain.

Neil is considering recommending that the Ecosulis team introduces ragwort seed into its meadow mix in an effort to encourage ant diversity and hill formation when rewilding agricultural fields in the future. “It’s an example of the way we are constantly refining our rewilding practices, going beyond what is already known and considered, disrupting received wisdom in land management for the benefit of biodiversity.”

We will continue our observations and we invite readers to do likewise and add their thoughts and insight in the comment box, or tag us in your observations on social media. “No doubt the more we look, the more we will see”, Neil concludes. In the science of rewilding, breakthroughs can come about as a result of lateral inductive links observed on the ground. 

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