DHBlog026 · An article by Jim White
Preface: In the recent article about Peter Hawes and his long-term research on grasslands there was one overriding concern: Grazing. Picking up on this theme, I thought it would be informative to ask Jim White to write an opinion piece on this topic, knowing it is often on his mind. The Editor.
When the editor approached me to write about grazing, as an opinion piece, my immediate response would have been: “Me, give an opinion? Oh, surely not”. I leave it to those who know me to judge if such a reaction were plausible…
The last Dorset Heath carried an obituary of my late partner Rob McGibbon. He was a serious conservation practitioner with his views based on his scientific background and, also, decades of experience. I re-found in his papers an unpublished letter he wrote to Plantlife in 2018, in mild and reasoned dispute with a view the charity had advocated: for road verges not to be cut until late in the season. With the indulgence of the editor and readers of Dorset Heath I reproduce his letter here, as the text for my ’Opinion’.
“In the editorial entitled ‘Road verges matter’ a reduction of nearly 20% in diversity since 1990 is cited. Much of this is attributed to nitrogen pollution. The decline is also linked to mowings left on the verges adding richness to the soil. I do not dispute any of this, but the assertion that mowing should be left until after flowers have set seed gives me considerable concern.
Until perhaps 30 years ago most road verges were cut to ensure that their summer vegetation was not excessive. For many verges this involved at least a cut in June and often a later one in autumn. The material of course was not collected but its volume was relatively low, and a proportion probably dried over the summer and blew away. Timing of the cutting appeared somewhat haphazard, and verges were not cut at exactly the same time each year; some flowers were of course cut in their prime; some re-flowered in the aftermath. The flowers took their chance with the mower, but the verges remained full of diversity.
Then there was a move in many counties to select the best road verges, mark them with posts, and give them more sympathetic management, leaving the cut until well into autumn. In just a few years, particularly on the naturally more fertile verges, the results were disturbingly evident. Aggressive species like false oat-grass and cow parsley had taken over and the rich diversity of plants, frequently including several species of orchid, had disappeared. Adjacent sections of verge not subject to this treatment ironically looked better than the ‘conserved’ ones. Clearly what had happened was that the single late cutting had allowed a few species to dominate, engulfing the many less competitive ones, and the effect was compounded by a dense thatch of cut material left to rot over winter.
I am afraid the mantra too often is “Let the plants flower and set seed” and this is applied to hay meadows and grazed grasslands as well as verges. Indeed, we should look to traditional hay meadow management as a model for our verges. They were cut to provide hay at its prime and unless abnormal weather prevented it, cutting took place in midsummer. Inevitably many flowers ended up in the swath but the grassland communities, adapted to this regime, thrived over the centuries. In perennial plant communities the need for recruitment from seed is low – relaxing the cutting regime occasionally is all that is needed.
Turning the spotlight on nitrogen pollution is right. It is a modern influence which is having serious effects on many of our habitats and perhaps, due to their proximity to the source, especially road verges, but this makes the need for cutting and indeed relatively early cutting, all the more necessary.”
Whilst Rob’s letter was addressing mowing, or lack of it, of road verges, the principles it sets out apply to most grassland, at least on moderately fertile soils in the lowlands, and to other methods of grass management including grazing.
In our climate, at least for the past 10,000 years or so, conditions have largely prevailed that enabled grassland to flourish on many soil types. Following retreat of the ice, a tundra-like vegetation would have ensued and then, as the climate warmed, trees were able to succeed. So, where does grassland come in? My understanding is that until humans removed them, there were large populations of wild herbivores, and other ‘soil disturbers’, such as aurochs (wild cattle), wild horses, deer of course, and wild boar. For some millennia, before the advent of organised farming, it is inconceivable to me that these wild, free-ranging herds would not have kept open glades and clearings in the prevailing forest, with differing soil types and locations of stress and exposure especially biased to grassland rather than wooded habitat. As we hunted to extinction the wild (and big and dangerous) herbivores, and their predators such as wolves and bears, we replaced them with domesticated livestock, and gradually contained and demarcated the landscape into defined fields and woodlands. For most of human history such grassland would have been comprised of a natural mix of wild grasses, sedges and herbs, reflecting soils and management practices. None of our predecessors would have planted the rich sward of chalk downland, or the flowery mixture of the traditional hayfield. Neither, patently, was their management down the centuries dictated by a concern for nature conservation! Rather, the flower-rich grasslands earned their keep as part of the agricultural system – as pasture or to provide winter fodder.
Only with the advent of mechanised farming and the availability of artificial fertilisers and herbicides – really over the past century or so – has the appearance of the single species grass ley become so common. The much-quoted statistic, that 97% of our ‘old’ hay field grassland had been lost between 1930 and 1980, is staggering and deeply concerning. What little is left is now, fortunately if belatedly, much more widely appreciated, for its conservation and biodiversity importance and its attractiveness and cultural value. The losses have not stopped altogether and more modern threats, such as atmospheric deposition cited in Rob’s letter, still take their toll. What would be unforgivable though would be for more loss of quality and subtle variation to be lost by misguided conservation.
In much the same way as traditional hay fields were mown when the hay was at maximum production and nutritional value – a variable time depending on each year’s weather but almost always around midsummer – so the downs and pastures were grazed at any time as needed; the fortunes of their diverse flora or the dependent insects were not a factor. Such management has persisted for centuries, even millennia, and as a result we have the flower-rich swards of classic chalk and limestone, and the billowing hayfields before they are cut.
Most grassland species are necessarily adapted to just such management: Long-lived perennials that don’t need to set seed each year or replace themselves very often; plants with rosettes close to the ground and growing points set low to avoid nibbling; or seed with a long persistence in the soil; or an ability to flower again after being cut or bitten off. As Rob’s letter points out, to hold off mowing (or grazing) in favour of all herbs being allowed to flower and set seed favours the few more aggressive and competitive plants. Much research, and my own half-century of deep involvement in nature conservation, tells me that it is the much greater range of less competitive herbs that will decline. Whilst winter grazing can be beneficial to remove any accumulated ‘thatch’ of under-grazed summer growth, grazing during summer – the active growing period of grasses – is essential for the long-term survival of the rich turf we all desire.
The lesson too of rabbits and myxomatosis is legendary and worth remembering. When the disease struck in the early 1950s and rabbit numbers crashed, the sudden flowering of the downs was remarkable. The downland plants had all been there, albeit with flowers regularly nibbled off. When that grazing was suddenly relaxed, the turf burst into flower. If grazing is prevented for successive seasons, in favour of all herbs being allowed to complete their cycle to seed production (and if we are honest, for us to enjoy!), it is coarse grasses like False-oat and Cock’s-foot that are the species to benefit, and the variety of less competitive herbs, sedges and grasses are the losers.
The moral is don’t be over-protective, and always consider the long-term conditions that have given rise to the habitat – here our grasslands – that we rightly seek to conserve.
Postscript: It seems that Rob’s letter was not acknowledged. In 2019, Plantlife produced the Leaflet: “Managing grassland road verges: A best practice guide” containing the exact same message that caused Rob to write to them the previous year. This guide is still promoted by the charity and can be downloaded from their website. The Editor