Lack of natural control mechanisms - the missing lynx
In a previous existence as a biochemist, I worked on the regulation of metabolic pathways, the dynamics of flux generating steps and flux transmission sequences. I looked at the properties of enzymes, and how their regulation by a multiplicity of factors, such as inhibitors and activators, allosteric modulators, substrate cycling, and compartmentation, controlled the potential flux through pathways. The more I look at wild nature now, and the control mechanisms of its natural processes, the more I recognise a connection, from the intracellular world of the enzymologist to the nature-led lands of wildness. Thus in my last job before quitting science, I was faced with the question of how the enzyme that catalysed the rate limiting step in the synthesis of a cofactor in fatty acid metabolism was ever active inside heart cells, even though we knew it was, because the cofactor itself acted as a feedback inhibitor, and there was enough of it around to totally shut down the enzyme (1). There had to exist something inside the cells that overcame that inhibition, allowing the pathway to function.
Metabolic pathways are integrated, appearing just like the interconnections of electrical circuits in wiring diagrams, and so I looked for other metabolites associated with fatty acid metabolism and tested a number of them to see whether they activated the enzyme. What I found was not an activator, but a de-inhibitor, overcoming the effect of the feedback inhibition, the concentration of the de-inhibitor increasing in the intact heart under conditions where the pathway could be shown to be active. The regulation that exists in natural processes, the control mechanisms within the different food webs and chains, must be what controls the flux through an ecosystem, and has implications for the state of the ecosystem and its vegetation dynamics. Do we understand what those control mechanisms are, and what happens if something is missing that should be exerting control?
Deer culling and tree colonisation
I was in Scotland a few weeks ago at a conference on National Parks (2). We travelled up the day before so that we could get a walk in the Black Wood of Rannoch, a fabulous remnant of ancient Caledonian forest (3). It’s a wood where you just have to dive in and wander about amongst its veteran Scots pine, birch and the odd rowan and willow, sometimes picking up the deer trails. Mostly damp, it has an acid heath shrub layer of heather, bilberry and crowberry, and masses of deadwood lying around, dripping with lichens and fungi. While Steve couldn’t resist climbing up into the canopy of some of the older pine trees, I was looking around for young trees as signs of the woodland regenerating. It took a little while, eventually finding a few nestled on the higher and thus drier tumps, avoiding what must be the many areas of puddling wetness when it rains. For that amount of seed source potential, there should have been more, and perhaps the deer take their share, but the woodland did not seem as grazed or browsed as I had seen before in Rothiemurchus.
The first day of the conference was a field trip, and we chose Creag Meagaidh National Nature Reserve (NNR). There was a briefing about the reserve and its deer management before a walk up into the hills took us alongside the water course of Allt Coire Adair, past an isolated area of birch wood, to some spectacular multiple buttress cliffs above a small loch, Lochan á Choire. There was still plenty of snow on top. Sheep were taken off the reserve area some decades ago in the 1970s, and then it was acquired into public ownership by the Nature Conservancy Council in 1985 (4). An original vision for extensive natural colonisation of woodland climbing up the hill had to be tempered years later by subsequent designation as a Special Area of Conservation for moorland habitats (5). Even so, the high population in the mid-80s of about 1,000 Red deer not only was preventing woodland colonisation, with the prospect that the birch woodland would die as seed sources were lost, but also degrading the snow level moss heaths, montane willow and moorland habitats (4). The decision was taken early on not to fence off the NNR to keep deer out – too large a task - but instead heavily cull deer if they were to see any natural colonisation of birch.
I should note that the Scots are quite keen on their upland birch woods, seemingly ubiquitous on the steeper hillsides that do not lend themselves to grouse moorland, as we saw travelling to the NNR. Their value is appreciated in favouring the growth of herbs like globeflower, and grasses, which are less common outside woods, and that they support a very rich bryophyte flora (lichens and mosses) as well as providing valuable habitat for woodland birds such as wood warbler, redstart and black grouse (6). In addition, birch wood rots quickly and thus provides valuable deadwood habitat for fungi, beetles and hole-nesting birds. I couldn’t help but comment to our group, as we saw the birch colonisation moving with us up the hill, that birch woods in England are given low regard, often being characterised as being species poor and having little value (7).
The focus on deer culling in the briefing made me uncomfortable. The reserve staff have become efficient slaughterers, making use of a dispensation to shoot out of season and at night (4). Ability to shoot the larger deer at higher elevation in the reserve depends on the means to remove the deadweight of the carcasses, which led to the upgrading of path surfaces all the way up to Choire Lochan, so that it could take All-Terrain-Vehicles without erosion and damage. There was also a new custom-built deer larder to cope with the carcasses. We were told that the annual cull of stags, hinds and calves had been around 140 in the last year, and that they now had a daytime density of only four deer per square kilometre. Quickly doing the sum for the 40 square kilometres of the reserve, I realised that they were culling pretty much the whole population each year. I raised this to blank looks in the room, and then the assertion came back that there were more deer at night, which suggested to me that there was obviously a displacement effect going on, with deer coming in from outside the NNR. However, they have maintained through decades of culling that this is not the case (4). It must be though, as shooting doesn’t instil fear – a deer has to survive to know fear, or at least witness an attack, and so there is no spatial deterrence from this culling (8). Since it is unlikely that wolf will be reinstated any time soon, it may be that we will have to train dogs to harry and worry deer, moving them on so that their browsing pressure is dispersed (9). This is a distasteful and probably illegal prospect – perversely, stalking and flushing deer with no more than two dogs is illegal if the deer are NOT shot (10,11) - but then this determined culling is also distasteful.
I won’t dwell on the conference session the next day, some of the speakers were appallingly bad – a nonsense bias about cultural contributions, and which George Monbiot ripped into as an uninspiring ambition - but then it was not a particularly good conference as it didn’t address the key issue of whether the Scottish national park model was any good. I got more from the field trip, my walking companion for some of it being Jeanette Hall, Scottish Natural Heritage (SNH) woodland specialist. As well as the birch woods, Jeanette is a fan of Atlantic hazel woods, predominantly found in the oceanic climate of western Scotland, and which I have also seen in western Ireland. These uncoppiced woodlands have stunning bryophyte populations, including a wonderful lichen called Tree lungwort (Lobaria pulmonaria) as well as many ferns and fungi. A report for SNH on these woodlands dispels many of the myths and misconceptions about hazel and coppicing that are held dear by the conservation industry in England, what the authors describe as the “hazel-coppice mind-set" (12). Thus it is not true that hazel is only an understorey shrub; that multi-stemmed hazel is all hazel coppice; that hazel will die out if not coppiced; and if it is not coppiced, that hazel will develop into a single trunk tree. Jeanette described to me that the greater age and size of the branches of uncoppiced hazel allowed for their extensive clothing in mosses and lichens.
Overgrazed Killarney oakwoods
Two weeks later, and I was looking at masses of Tree lungwort growing on a fallen oak tree in Tomies Wood, Killarney National Park in Ireland. Tomies Wood has fabulous old oaks, clothed in mosses and lichens, and many large, tree-like hollies, but it had an incredibly chewed understorey: no brambles to be seen, nor any young trees or seedlings, the woodrush pathetically short, and the hollies almost de-barked. It was nothing less than bizarre, and while it was nice to see groups of the non-native sika deer in there, this is a woodland that could die. There is a long history of grazing by sheep and deer and its impact on Killarney oakwoods, resulting in a severely overgrazed herb layer, complete absence of effective tree and shrub regeneration, and a browse line on the holly (13). Exclosures were erected in the early 70s in Tomies Wood that resulted after six years in large numbers of holly seedlings becoming established, both woodrush and bilberry flowering and producing fruit, and ferns producing fertile fronds.
There are still exclosures in Tomies Wood, many older exclosures that were former study sites, but also over 7ha of exclosures have been set up in areas of clear fell of plantation trees, some of these new exclosures having been planted with oak and others left to regenerate naturally (14). I looked into some of them, and while the trees are developing within them, they are still missing a lot of the basic understorey species. By way of contrast, I walked in the nearby Ross Island woodlands, also in the National Park, and known to support one of the richest herb layers of the Killarney woods (15). I found three different orchids including the very odd Birdsnest orchid (Neottia nidus-avis) its light brown colour making it appear dead, but it is without the green of chlorophyll, living instead by parasitizing fungi that live off trees. There was still wild garlic and bluebells in flower, and many lovely ferns. As ever, the wood dripped mosses and lichens, the oak, ash and birch giving way to alder carr in the much wetter areas, this more open woodland full of yellow flowering flag iris. There were signs of a deer presence, but the peninsula nature of Ross Island, and the waterway that cuts across at its narrow neck, must be an inhibition to a threatening presence within the woodland. Perhaps this is fortuitous, as there is no national deer management policy in Ireland, and no co-ordinated system of deer population distribution or density measurement (16) although a Draft Policy Vision for Deer Management in Ireland was put out for initial consultation in 2011 by the Forest Service in the Department of Agriculture, Food and the Marine, and is now in its second draft (17,18). In the meantime, fencing, and the difficulties of its use at large scale, are thus the recourse in the Killarney National Park to keep its woodlands alive (14,17).
The importance of large carnivores in natural processes
Roe deer grace my local woodland, adding an
atmosphere of wildness by their presence. I don’t always see them, but I
know they are there from their trails and scrapes, and not from any damage
they do – grey squirrels are more damaging. If there is culling, then I am
not aware of it, other than a remark once from a council officer that the
strategy for deer control in the District relied on poachers. I certainly
don’t live in one of the priority areas identified by the Deer Initiative
on the basis of damage to woodland SSSI, deer-vehicle collisions,
agricultural damage and animal health issues, and where deer are
“humanely” dispatched through “collaborative deer management”
(19). Many years ago, I complained about a lack dignity afforded to deer
in a consultation on their management, the absence of an explanation of
their natural behaviour or habitat, nor indications of geographical
locations in Britain where their unhindered presence could be welcomed
(20). A subsequent consultation was held on proposed changes to the Deer
Act 1991 (21) the proposals from the consultation forming the basis of the
Regulatory Reform (Deer) (England and Wales) Order 2007 (22). In effect,
the Order just made it easier to kill deer by the “increased range of
tools available” to the killers, and which “will enhance deer
welfare” (23). The Mammal Society supported many of the
recommendations for the Order, but had a very interesting Conclusion to
their consultation response (24):
I have made this very same argument (20) but also advocated the reintroduction of lynx as a natural predator of foxes so that they are an alternative to the slaughter of foxes every year in the name of predator control by the game-bird industry (25) and for the atmosphere of wildness that lynx will bring, as well as seeing the results of their influence on the vegetation of our landscapes (26).
The importance of large carnivores in natural processes cannot be overstated, although you would be hard pressed to find someone in the conservation industry here that has a real grasp on this, and why discussion on vegetation dynamics has to raise its game from just advocating sticking excrement producing livestock within fenced areas (27). The greatest possible dynamic interaction in natural processes comes when the functional or trophic diversity is greatest, when species are present in all trophic levels of a natural system, such as top predators like the wolf and lynx; middle (meso) predators like the fox and pine marten; the plant eating herbivores; plants; carrion; and detritus feeders (28). A trophic cascade occurs when the animals at the top of the food chain - the top predators - modify the behaviour and numbers of their prey, but also affect species with which they have no direct connection (29). Thus their impacts cascade down the food chain, in some cases radically changing the ecosystem, such as maintaining the vegetation cover of a landscape in the face of herbivore pressure, providing food resources for scavengers, and even enriching the composition of soil from decomposing carrion (30,31). That there is a lack of natural control mechanisms in areas where carnivores have no presence is shown by the increased numbers of wild herbivores in the modified landscapes of human use across Europe, especially different deer species (32). The impact of this increased herbivore pressure is seen in its negative influence on tree colonisation and tree species, and on the diversity of herbaceous vegetation. Thus top predators are the de-inhibitors, overcoming the effect of herbivores in their inhibiting of the growth and colonisation of trees.
Where should we reintroduce lynx?
My thoughts about reintroduction of lynx were against the backdrop of the Craven Limestone Complex in the Yorkshire Dales, because of the finds and dating there of fossilised bones providing one of the nearest temporal links to a once presence in England’s landscape (20). As I noted, the generally low woodland cover of the Craven Limestone Complex was not a recipe for reintroducing lynx with any confidence that a breeding community would establish. A larger scale of potential habitat was identified for the possible reintroduction of lynx to the Scottish Highlands, but much of that was non-native spruce plantation rather than native trees, thus raising issues about our knowledge of the quality of this habitat for lynx (33). A scoping study in Wales concluded that a main limiting factor was the lack of woodland, especially native woodland, and the level of disturbance in plantation woodland, of clear felling and replanting, means that much of this at any time would be unsuitable habitat for the lynx (34). There were also concerns about the scarcity of roe deer by comparison with England and Scotland, but that numbers were increasing. The authors did, however, make a significant point in that large predators are not constrained by political boundaries, and so a re-introduction of lynx should be planned at a British level, and not just considered for Wales alone.
I am not aware of any recent feasibility study for the re-introduction of lynx to England. However, a recent Europe wide spatial study identified potential core habitat areas for large forest-based mammals, and analysed the connectivity between them based on landscape resistance i.e. the permeability to migration of the mammals. The modelling used the lynx as the focal species, setting a requirement for core areas of forest densities of 50 % or more, and a size that would accommodate a minimum viable population of 20 lynx. Because of the much greater forest cover in continental Europe, it is unsurprising that 134 potential core areas were revealed by the mapping, as well as 209 opportunities for linkages between these core areas (see Map 4.4 – (35)). There were also two core areas in Britain: one in North Wales, the other in North Yorkshire, and with the potential for a wildlife corridor of about 240 km running between them.
I know the core area in Yorkshire as the complex of around 130 square kilometres of plantation woodland in the Public Forest Estate inland from Scarborough, and which includes Broxa, Cropton, Dalby, Harwood Dale, Langdale and Wykeham Forests. The core area identified in Wales is also plantation woodland in the Public Forest Estate of around 110 square kilometres, including Clocaenog Forest west of Ruthin, and the Gwydyr Forest Park that encompasses Betws-y-coed. What is surprising is that the core area mapping didn’t pick up the larger plantation forest complexes that exist in Britain, such as the 565 square kilometres of Kielder Forest in Northumberland, and the similarly sized Galloway Forest Park in the Scottish Borders, and with a much shorter distance of around 120 km between them for a potential linking corridor. Irrespective of this, the evidence of this mapping is an indictment, and which follows on from our low woodland coverage compared to the European average, that the largest forest areas we have are plantation forests rather than native woodlands.
The pattern of existing deciduous woodland is of much smaller areas, and with varying tree density compared to the uniform and efficient spacings of conifer plantations. Nevertheless, a few years ago, Steve and I used the deciduous woodland inventory of Britain at the 1km scale to identify areas of higher woodland cover. We had to set our sights quite low compared to the European core habitat mapping, using a threshold of 15% cover, which is just over the national cover of around 12%, and with two higher boundaries at 17.5% and 20% cover (36). As we expected, the 20% boundary in our mapping picks out a large area of SE England, including E and W Sussex, Surrey and W Kent, as these counties are shown to have the highest woodland cover in the National Inventory for Woodland and Trees for England (see Fig. 5 in (37)). Thus, for instance, in Surrey, the county with the highest tree cover, the Waverley Borough Council area is 30% wooded (38). I have no easy answer as to why so much woodland cover is concentrated in the SE.
Our mapping does pick out other locations with a core area of 20% cover, and with surrounding bands at the lower boundaries of cover, including a swathe from Luton to Maidenhead; the New Forest, centred on Lyndhurst (600km2); an area to the east of Dartmoor, between Exeter and Ashburton (403km2); between Ross on Wye and Chepstow, including the Forest of Dean (305km2); a similar sized area between Canterbury and Ashford in E Kent; and a central part of the South Lakelands area concentrated around Newby Bridge (208km2). A second level of higher cover, with core areas of 17.5%, picks up an area in the eastern Peak District between Wardlow, past Bakewell and Matlock to just N of Belper (393km2); from Pontypool via Caerphilly to Pentrych in S Wales (295km2); an area to the W of Kidderminster, that includes the Wyre Forest (248km2); and between Cheltenham and Stroud (200km2). Scotland is poor in terms of deciduous woodland in this mapping context, with only an area around Loch Rannoch and Loch Tummel in Perthshire being picked up. Perhaps we would find more in Scotland if we were to use the most recent native woodland survey, and which combines native pine with deciduous trees, but excludes non-native conifers (39).
Not all of these areas of higher woodland cover that we identified, while they are of substantial size, are necessarily functioning ecologically as wooded landscapes, and may thus not be suitable for lynx reintroduction. As was alluded to earlier, a landscape with only 10–20% woodland cover has probably a large number of small, isolated woods, so that there is little or no core area, and edge habitats are relatively minimal. When woodland cover reaches 30%, small woods clump together to form larger woods, ecological isolation is reduced as patches start to coalesce and edge habitat becomes substantial – the landscape is thus functioning as woodland (40).
Opportunity mapping for new woodland creation
It is these kinds of opportunity mapping – ours and the European study - that begin to tell us whether we can return the missing lynx, balancing the need for higher woodland cover with adjacent human population density and thus likely conflict, although lynx are not a direct threat to humans and their impact on agriculture is overstated. It will indicate also whether we do in fact have high enough woodland cover for the lynx, and where would be the best places to increase woodland cover. Is it better to build on existing areas of higher woodland cover, and then create linkages? A range of opportunity mapping does exist for woodland creation, such as that for reducing flood risk in England, and which shows the degree to which river water bodies in England are free from constraints and sensitivities to woodland creation (see Map 5.10 in (41)).
Another approach recently came from the Natural Capital Committee, an advisory body to Government, in its exploration of integrating the economic value of Natural Capital into decision-making on the provision of Public Goods, and enhanced value for money in public spending (42). The Committee developed a case study for Britain’s New Woodlands in which England, Wales and Scotland each plants 250,000ha over 50 years, giving a total of 7,500 square kilometres of new woodland, or roughly 3% of land area. Their analysis examined the costs and benefits of planting in each and every location in Britain and chose those which maximised net values, the results markedly dependent on whether effects on non-market, natural capital goods were included. Thus the location of areas of woodland planting predicted on the basis of costs of planting and subsidies, compensation for agricultural losses, and for timber production values, were predominantly in the upland areas of all three countries (see left hand map of Fig. 4.2 in (42)). Because the timber values are lower than the value of the displaced agriculture, taxpayers would have to pay compensation to farmers in order to induce them to allow the afforestation to go ahead. If instead, recreational values were maximised along with timber values in deciding where trees would be planted, then there was a dramatic shift in the location of Britain’s new woodlands, bringing them off remote upland areas, adding a green fringe of woodland around Britain’s major population centres, significantly improving water quality, the non-market goods generating massively higher value for money, easily outstripping the foregone value of agricultural production (see right hand map of Fig. 4.2 in (42)).
It is tempting to speculate that these latter locations, and particularly their spatial distribution that appears to create large groupings with higher woodland cover, significantly reducing the presence and influence of agriculture, could be a significant draw to burgeoning deer populations, and thus could be ideal territory for re-establishing lynx.
Mark Fisher 14 June 2014
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