From Nigel Spring –
This is part 3 of a four-part article. Since 2012 a team of volunteers and contractors working through EuCAN Community Interest Company and Butterfly Conservation has been working on the chalk downland sites between Lyons Gate and Godmanstone to remove the invading bushes and trees that are threatening to destroy the last vestiges of this incredibly biodiverse habitat in this area of Dorset. The plumes of smoke from the hillsides on Thursdays between September and March cannot have gone unnoticed…..
We are very fortunate to have a number of well-known and highly regarded chalk downland sites in this area of Dorset – good examples are Black Hill, Yelcombe and Giant Hill above Cerne Abbas; Lankham Bottom Butterfly Reserve above Cattistock and Hogcliff National Nature Reserve above Frampton and Maiden Newton.
But look at a map of Dorset and the UK and you will see that the chalk stretches from west Dorset at its SW corner to Yorkshire and Norfolk at the northern end and into Kent to the east. So why is this habitat such a rare commodity? In centuries past, the downs were grazed by large numbers of roving sheep flocks, while only steep flinty, less productive slopes would have been maintained as woodland (some of these ancient coppices still remain). Hawthorn, gorse and bramble would have been far less abundant, some it cropped as furze for fires, but most of it nipped off by the flocks as they passed through.
Our ancestors would have cultivated some of the hilltops and the slopes but on a very small scale as the human populations were so low. You can still see relics of the celtic field systems in the Cerne, Sydling and Frome valleys, many of them pre-Roman. Chalk grassland and the butterflies and other wildlife it supports would have flourished from east Devon to Kent to Yorkshire.
Previously open stretches of chalk countryside were divided up by the 18th century enclosures but it was after the end of the second world war that the widespread arable cultivation of downland took place, with the government encouraging farmers to ensure that we would never again be vulnerable to being starved into submission.
The scale of these operations has accelerated enormously during the last fifty years with the help of advances in technology which have not only given the farming industry larger more powerful machines to work on the steeper slopes, but also the chemicals to ensure that rivals for their growing space like insects and weeds (aka wildflowers) have become reduced to a minimum. Chalk soils drain very freely so fertilisers tend to get leached out of the ground by the rain. The free drainage and lack of organic matter in the soil mean that arable crops have to be treated continuously with fertilisers as well as pesticides and weedkillers.
The consequence of this arable revolution that began at the beginning of the 50’s is that chalk downland habitats have become reduced in Britain by over 90% , with the remaining sites now being restricted to steep slopes. Very few flat downland sites are to be found now – Martin Down on the Dorset/Hampshire border and large parts of Salisbury Plain still survive thanks to the involvement of the military.
Further information can be found on the EuCAN website http://www.eucan.org.uk/uk/dorset/cerne-valley-project/