Conservationists constantly worry about how to ‘keep things going’ – be it a bird, butterfly, or some other organism teetering on the brink. It is a pretty sad state of affairs, but that’s the deal by now. It takes a lot of dedication by a few, in the face of indifference by the many, to stand against the flow of wildlife disappearing down the plughole. Last summer I came across a vivid example of what it takes to keep things going.
Not far from where I live is a scruffy looking, overgrown meadow in a nowhere-in-particular sort of place. The rushes and grasses are knee high and tussocky, birch saplings and sallow bushes threaten to overrun it. Although it doesn’t look much it is in fact carefully cared for. On a sunny day in June I went there with my friends Annie and Andrew to count marsh fritillaries, one of Europe’s fastest declining butterflies. Annie and Andrew have been committed to keeping marsh fritillaries going on this seemingly forgotten piece of land for years. We were careful to walk the same route for the same length of time as previous years, so comparisons could be made. As we waded through the long grass scattered with ragged robin and heath spotted orchids I discovered just how wet the meadow was: the water flooded over my boots and I soon had wet feet (my companions were wearing wellies!). The marsh fritillaries were surprisingly easy to see flying low over the vegetation and settling confidingly to bask in the sun. Seen in flight they were a dull coppery brown but up close a beautiful chequered pattern of cream and orange, with conspicuous yellow tips to their antennae. We counted forty-four butterflies, a good total by all accounts.
The essential, non-negotiable ingredient for marsh fritillaries in these wet meadows is devil’s-bit scabious, the exclusive food plant of their caterpillars. This place had masses of it, although in June it is just leaves, the delicate blue flowers would not appear for another couple of months. At this season the butterflies were mating and laying their eggs in batches on the underside of the devil’s-bit scabious leaves. On hatching the bristly black caterpillars spin a collective silken web for protection, within which they feed on the scabious leaves. Once they have consumed one plant they migrate en masse to another, spin a new web and repeat. We went back again in September (I was wearing wellies this time), to count the larval webs, which by then were bigger and more conspicuous as the caterpillars had grown. It was a bit like searching for soggy bits of Kleenex discarded in the long grass. We found about 70 webs, each with small black caterpillars curled up inside. Each one was marked with a cane, and afterwards Andrew used some neat IT skills to plot them precisely on a map. All of this counting and mapping gives us a fair idea of how marsh fritillaries are doing year on year.
The other essential part of keeping things going is managing the habitat. We have no real idea about the ‘where and how many’ of marsh fritillaries before humans began modifying the landscape. What we do know is that in this part of Britain they adapted well to damp, lightly grazed pasture land that contained devil’s-bit scabious. Sadly over the last 60 years or so the majority of such places have either been drained and agriculturally improved or heavily grazed by sheep. The latter is a big problem for marsh fritillaries as devil’s-bit scabious is highly palatable to sheep, and with even moderate grazing they will wipe it out, taking the butterfly with it. Some years ago, having found the marsh fritillaries here, Annie negotiated with the estate that owns the land and they, to their credit, agreed not to graze it but set it aside for the butterflies. Annie then persuaded a local stable to put 3-4 ponies on the meadow in the summer time to reduce the coarse vegetation that can crowd out the devil’s-bit scabious. Cattle, unlike sheep, do not prefer devil’s-bit scabious, and horses avoid eating it all together, which makes ponies the ideal grazers here. Despite this, getting a level of grazing that ensures the devil’s-bit thrives, yet sufficient numbers of butterfly eggs and caterpillars survive the trampling of the ponies, is a tricky business. What is more the colonisation of the grassland by sallows and birches seems to be unavoidable with this level of grazing, so in the winter Annie and Andrew spend time cutting these out. This is an on going commitment as the meadow would eventually become a young wood if left to its own devices. If any part of this carefully constructed regime were to fail the butterflies could be lost within a few years.
In Britain marsh fritillaries are now often confined (very unnaturally) to small islands of suitable habitat. Maintaining optimum conditions for a single species year after year on a small site is very difficult. Insect populations can fluctuate dramatically in response to weather, parasites and the condition of the vegetation. In an extended mosaic of more or less suitable habitat that would not matter much as they could move about as conditions changed. But these butterflies are now ‘caged in’ and entirely dependent on two unpaid enthusiasts and the estate that owns the land to keep them going. You might ask ‘why bother?’ – not many people would miss the marsh fritillary. I can only answer that for me it would mean one more spark going out in the firmament and another small step towards the darkness.