|Duddon valley - woodland now and into the future|
The more I read more about woodland, the less certain I become that the woods we have today in Britain bear much of a resemblance to what would be the natural distribution of native trees species. Itís not just the frost-damaged beech, ill-advisedly planted in Scotland and elsewhere so that it is outside its natural range. The books recount a pervasive human influence. This is because the history of woodland as a natural habitat is irrecusably linked to human intervention and exploitation, as would be expected from our early reliance on its wood and timber products, and for the sustenance we could draw from its overall community of woodland fruit, nuts, mammals, birds and ground flora.
The more you value the benefits of a natural resource, the more you would have expected it to have been tended to ensure its natural richness and enduring presence. Our lust for farming, however, broke our dependence on woodland as the growing of grass and cereals was incompatible with the dominance that woodland had in the landscape. It is surprising that such a small population of some 50,000 people could have set about the wholesale destruction of woodland so effectively that in a few millennia it would drop from a coverage of over 70% to something like 15%, while our population grew to two million. We should not overlook the other significant agency of change Ė the farm animals that we introduced to our countryside and which kept the cleared areas open, but as importantly prevented the natural regeneration of much of the remaining woodland. The deforestation of our landscapes thus became ingrained in our culture, ensuring that livestock had access to pretty much all of our land area. In the last 1,000 years, we exported that livestock driven approach to farming to temperate regions around the globe.
Spirit away the influence of people
You just wonder what would happen now, if we got rid of the influence of farming from our landscapes, and perhaps also our propensity in Britain to farm woodland as mono-cultural plantations in the same way that we farm animals. A somewhat apocalyptic article in New Scientist last October tried to assess how the earth would bounce back if the worldís population of 6.2 billion could be spirited away (1). The author did not also spirit away farm animals, but the speculation was that cattle and other livestock, bred for meat or milk, are likely to persist, though in much fewer numbers than today. After centuries of artificial selection and inbreeding, these farm animals will probably evolve back towards hardier, less specialised forms through random breeding, and finding niches in many ecosystems in the same way that feral horses, goats and pigs already have.
In one sense, this would be a re-introduction of wild species extirpated by our early ancestors and up into recent history. Thus the long lost aurochs were the fore-runner of modern day cattle; there is some evidence of the presence of truly wild horses early on in post-glacial Europe; and wild boar roamed our woodland. As with the feral goats we already have, the feral sheep would be out of place in Britain, but Mother Nature would likely find a solution. The article highlights the city of Pripyat near Chernobyl, which became a deserted exclusion zone for people after the nuclear disaster 20 years ago. Now, roots from encroaching vegetation are breaking up concrete and buildings; wild boar are 10 to 15 times more common within the exclusion zone; and big predators such as the wolf are making a stunning comeback. Wolf we donít have now, but perhaps we should better appreciate the intrinsic value of foxes, the natural predators we do have.
That Mother Nature can adjust when landscapes are threatened by herbivores is shown by the example of what happened on Isle Royale, a large island in Lake Superior. In the early 1900ís, moose swam across to the island, multiplying in their thousands where they had not been before as they found the regenerating logged areas highly palatable browsing. Once the island became a National Park, the extent of browsing and the health of the woodland became a concern, leading park authorities to consider introducing wolves. However, the problem solved itself when during one cold winter, the lake froze more extensively, and a wolf pack from Canada travelled over the ice and began predation of the moose.
So much for animals, what about plants and trees?
The article conjectures that areas still rich in native species will recover faster than more severely modified systems. The native boreal forests of northern Alberta, Canada, have little present day human intervention other than a few access roads, forest rides and pipelines. Simulations carried out by a land-use ecologist indicate that the forest will close over 80 per cent of these within 50 years.
Where native forests have been replaced by plantations, it may take a few generations of trees, perhaps several centuries, to lose their mono-culture and work their way back to a natural, mixed forest state. They will, provided of course that there are some remnant native species within or close by. This is the assumption behind the policy in England that looks to the regeneration with native broadleaves that is expected to occur on our ancient woodland sites where the plantation conifers are to be harvested and not replanted.
The article then turns to the vast expanses of rice, wheat and maize that cover the world's grain belts and which may also take quite some time to revert to mostly native species, but here the slowness of the transformation is guided I firmly believe by the extent of our modification of the landscape. One thing I have learned over the years is that we can plant a tree almost anywhere, and provided we havenít got it totally wrong, there is a good chance it will thrive as we will give it a great start with the right stuff around its roots, a surface mulch to lessen competition, and probably spend as much money again or more in physical protection. However, if we were to scatter tree seed in the same place, it may not establish there, and for a number of different reasons: lack of a cold period for stratification; eaten by something as a seed, or later as it lacks a protection from thorny bushes; it may not have the right soil conditions or leafmold cover; it may lack a mycorrhiza fungi, or frankia bacterium etc. Thus there is a world of difference between natural regeneration/colonisation and us going out and planting things. Nature is more complicated.
We also have to accept that our agriculture has fundamentally changed soil conditions, with the years of spreading lime and phosphates onto the land, putting in drainage everywhere and smoothing out the landform, such that we now have a flora of agricultural and disturbed ground fellow travellers that revel in these conditions and which may resist or swamp out all natural recolonisation, including any ground flora regeneration in new or regenerating woodland (see, for instance, 2).
Other more contemporary horror stories exist
One pessimistic author has it that the days of hazel naturally regenerating in England have almost gone because of the widespread distribution of the non-native grey squirrel (3). Dutch elm disease, while it killed off 90% of trees in the 1960s did not kill all of them, especially if it was a big clonal ring in woodland. The survivors however now grow little larger than a coppice stem before die-back occurs again. Oak no longer regenerates inside woodland as the mildew disease introduced from America in the early 1900ís has spread across Europe. The whitish bloom of the fungal disease on the leaves makes a young oak more sensitive to shade. We are suffering the curse of introduced trees such as the larch and sycamore, seeding themselves around with abandon, with laurel and rhododendron choking the life out of our undergrowth, and with Himalayan balsam disfiguring it, all adding to the sense of a hybrid landscape.
Sometimes you can see a clear pattern in nature. I love the alder carrs growing next to the becks and gills, and in the flushes in my local ancient woodland. At this time of year, the flushes are patterned with emerging pink flowers of butterbur, along with early signs of marsh marigold and angelica. Alders have a narrow habitat requirement of moving water, and you can often see them growing on their own, alongside water courses where its water-bourne seeds germinate along flood lines. As for the other trees in the woodland, I see some of the hazel in parallel rows, the birch is pretty random except where it seems to form a small wood pasture, holly is on the up, wych elm is sparse as is elderberry, but who put in the sycamore and I just donít know about the straight-up oak and lack of oak seedlings. I need to see more ancient woodland and be able to watch new woodland grow.
Duddon Valley Woodland
Just such opportunities can be found in the Duddon Valley, which lies in the south-west of the Lake District National Park, and with its river runs northwards for 10 miles from Duddon Bridge to Wrynose Bottom. Itís a narrow river valley, not more than a mile wide, and which has a band of woodland, except for a few very small breaks, stretching all the way up along the western side of the valley, often by the edge of the river.
A number of things make this valley woodland special. Hardknott Forest, at the top end of the valley, is a Forestry Commission (FC) plantation (600 ha) that was planted in the 1930s and 40s, and is currently reaching the end of rotation. Clear felling has occurred annually since the late 1990's and the intention has been to allow mostly natural regeneration from the remnant stands of native woodland within the plantation. It will not be replanted with conifers.
Below the plantation and running down to Duddon Bridge, is a chain of 22 ancient woodland sites, the majority of which are covered by the Duddon Valley Woodland Site of Special Scientific Interest (SSSI 360 ha). This is one of the largest series of woodlands in the Lake District, the others being Borrowdale and Ullswater. Different woodland communities are associated with the different soil conditions found along the length of the valley. However, the most widespread community, is upland oak-birch woodland, and it is one of the largest areas of this type in the Lake District. The notification for the SSSI describes a resplendent ground flora that would be expected of this ancient woodland. Most of the woodlands are on moderate to steep slopes, and although few have much of a footpath system through them, there are a good number in the northern half of the chain that are included in open access.
The spatial relationship between the regenerating plantation and the ancient woodland is what makes the Duddon Valley irresistible for me. The FC are obviously taking note of this, and will be monitoring the regeneration of their plantation with native broadleaves (as will I). Its tough going in the mess of the clear-felled areas of the site, but you can see a sequence of birch, rowan and holly corresponding to the years since clearance. Small areas have been fenced off to provide a measure of the browsing pressure that the regenerating woodland is under in the wider plantation landscape.
To give nature a bit of a hand, and to fill in the link southward to the ancient woodland, the FC have planted up 40 ha of intervening open fell with patches of juniper, oak, holly, hawthorn and birch, and there are patches of advanced natural regeneration already going on there. The whole has been exclosed with high deer fencing and the area is badged as Grassguards Native Woodland. It will be interesting to watch this grow and compare what happens to the fell on the outside of the fence.
We popped into a few of the ancient woodland sites, and it was quite a lesson. Rainsborough Woods (32 ha) has a fabulous community at its top end, with emerging native daffodils and wonderful clonal rings of aspen. However, below this the majority of the wood was replanted at some point with beech and its woody understory has been cleared-through, as is common in plantation management. On the other hand, the northern end of Wallowbarrow Coppice (31 ha) has again some very old rings of aspen, some wonderful spindly oak, birch and holly, and a fabulous (very fabulous) collection of bryophytes on the woodland floor. The biggest disappointment was Great Wood (8 ha), an isolated island of ancient woodland nearest to the plantation, and from which there could be great hopes for transference of woodland species. Except that Great Wood is an enigma (it is not part of the SSSI). It has good oak, although of even age, but very little else. The ground layer has some bryophytes, mostly over wet rock surfaces, but the predominant species are tough moorland grasses. No ferns, one holly, little chance of any geophytes, and hardly any sign of woodland regeneration. There is more variety in the rock ledges either side of the River Duddon immediately below the wood.
There is a long tradition of using upland woods as shelter for sheep and grazing. Thus it is likely that this wood has been over-grazed in ecological terms, leading to the loss of its distinctive plant communities. The new stock fencing around this FC-owned woodland is perhaps recognition of this. Isnít it sad that this ancient woodland is in need of native regeneration itself?
I cannot leave the Duddon Valley without mentioning the area of juniper, yew, holly, rowan, birch, and aspen on the open fell of the eastern side of the valley, below Yew Pike and Cinder Hill. It doesnít rate being marked as woodland on the map, it is unlikely that any of it was planted, and we just love it as a community of trees.
Mark Fisher 24 February 2007
(1) Imagine Earth without people, Bob Holmes, New Scientist 12 Oct 2006
Predicting Site Suitability for Natural Colonisation: Upland Birchwoods
and Native Pinewoods in Northern Scotland, Richard Thompson,
Forestry Commission Information Note 54,
(3) Woodlands, Oliver Rackham, Collins, 2006