Barn owls confound the conservation industry


Snow makes even a mundane landscape look good, and a good landscape even better. The accumulating days of coldness has led to icicles the size of my arm building up on the waterfalls and edges of a favourite moorland beck. Few people ever walk up the deep, narrow ghyll, and the lack of footprints in the snow tells me that I am the only person who has been to see these “organ pipes” of ice. I am not however the only creature on the moor. Measure the stride and note the placement pattern, and the traces reveal who has already passed that way. Thus rabbits track to and fro, but the spindly claw marks of birds appear where they landed and disappear on take off. Roe deer at speed leave single points at wide spacing that become multiples when they slow down. Smaller mammals leave grooves or tunnels in the snow, as they use its cover as protection against raptors. Every creature is thinking about food and how they are going to find it now that the endeavour has been made much harder.

It will be a tough time for herbivores. I didn’t see any sheep on the moor, but farmers were spreading out hay in the intake fields just off it. Cows of course are already indoors now as there is little for them to eat even when there is no snow. It’s tougher for the free-living animals. The snow of last winter melted to reveal many dead rabbits, and there were reports of deer dead from starvation in Scotland. It makes me wonder how it is, when over 50% of the British landscape is grazing land, that a hard winter and snow puts herbivores whether wild or domesticated on the edge.

It also puts into perspective the clamorous claims of the conservation industry that grazing is a natural part of the landscape, especially since Natural England has just had to relax the rules during this snowy weather on supplementary feeding of livestock for farmers in agri-environment schemes like Higher Level Stewardship (1). Last year, I took a pop at the craze for conservation grazing, justified by the conservation industry on the back of the “Vera hypothesis” of large herbivores as a natural shaping force in landscapes. The hypothesis was a gift to the conservation industry, as it appeared to validate their command and control approach to nature conservation of slinging up fences and pushing on domestic livestock, all fuelled by the Higher Level Stewardship scheme. It’s a hypothesis full of holes, some of which I explored (2).

Then I looked at the ecological or evolutionary legitimacy of grazing. I traced the paleoecological evidence of the distribution of fossil pollen and the fossil bones of extinct herbivores and carnivores that could differentiate between an open or closed landscape, and which would have been the post-glacial, natural matrix for Britain (3). I feel compelled to return to this again because those ideologically wedded to open landscapes get away with their presumptions without ever having to substantiate them, nor take a systems approach to understanding landscape cover. A number of things have pushed me to do this.

Fencing and grazing on the Malvern Hills

a local action group opposed to areas of the Malvern Hills being ringed with electric fences and paths blocked by gates (4). They supply a list of newspaper reports going back 10 years that trace their disagreement with the fencing and grazing proposals of the Malvern Hills Conservators. It is such a familiar, depressing story - arrogant Conservators, bogus claims on biodiversity, the financial inducement of agri-environment schemes such as Higher Level Stewardship, fencing, cattle grids, and the re-imposition of sheep grazing after 50 years etc. etc. - relieved only somewhat by the fact that, unusually, two of the members of the Board of the Conservators were against the scheme. However, what really brought a wry smile was the loss of 56 sheep owned by the Conservators, undiscovered for many months, and the resignation of the shepherd before an investigation could be launched into how the sheep disappeared. The local action group continue to harry the Conservators because they don’t believe the Board has the legal power to fence any part of the hills for stock-management purposes (5).

Recently, the Conservators announced a winter long program of scrub clearance that made it into the Malvern Gazette. The article attracted a lot of comments, questioning the basis for many of the actions on the Hills. In reply, Rob Havard, Conservation Officer for the Conservators, gave this rationalisation (6):
‘I have sympathies with the "let nature take its course" approach. However, "nature" includes keystone species like wild grazing herbivores and the grazing scheme is a way of re-creating the natural processes that these, now extinct species, would have carried out in a "natural system". The plants/flowers and butterflies that depend on them have not just evolved since the advent of agriculture they were around before it and so these habitats that rely on grazing obviously had a decent supply of grazing before we humans interfered’

I will come back to this remarkably naïve and unsubstantiated set of claims that is the typically convenient justification given by the conservation industry.

A dogma too far

I picked up on an adverse comment to an article about a study that concluded that fencing off streams and drainage ditches so that farm animals can't deposit manure in and around them could cut levels of faecal pollution. The ideology of the open-landscapers to the fore, Neil Sanderson remarked 76):
“With fencing, if biodiversity is not to be greatly impacted then grazing needs to be replaced by even more expensive mowing to prevent dominance by tall ruderal vegetation and later uniform dense shade by shrubs and trees”

This was a dogma too far for me, and so I responded that it did, of course, depend on what "biodiversity" was being counted, and that riparian woodland is of high value in ecological networking through farmed landscapes. Thus fencing off of water courses so that this can be restored is an important approach in Forest Habitat Networks (8). I also lamented that floodplain woodland is missing from Britain due to agricultural expansion, when it is a common habitat in many countries across Europe, and would continue to be absent in Britain if there is a false emphasis on the open landscape species dependant on farming. I was then rebuffed by Keith Alexander, a colleague of Sanderson:
“'A false emphasis on the open landscape' reveals your theoretical and hypothetical starting point. There is very strong evidence for a naturally open landscape in Britain but the palaeo-ecologists are still in denial! We need to separate facts from hypothesis when managing land”

I will of course go on a search for this very strong evidence.

The pervasive influence of cultural landscapes

Perhaps the most worrying thing about this presumption for grazing being a natural process is that it is being pursued now with vigour by some western Europeans as a means to create “new wildland”, and on the back of the momentum initiated by the resolution on wilderness passed by the EU Parliament (9). A high profile project conceived last year started out as the Wild Europe Field Program, and with the intention of spreading the Dutch experience of nature development through the use of grazing herbivores. Its website contains an explanation of the projects approach under the heading "Wilderness is more than forest alone" (10):
“many people believe that the more open European landscapes are originally agricultural lands, while in fact most European plant and animal species originated in tandem with the original wild grazers ….marginal agricultural areas are being abandoned on a large scale and are forested spontaneously………plants and animals in half-open and open areas are at risk. That is to say: much of Europe’s biodiversity……… To turn the tide, a new appreciation of the original role of the great grazers must prevail”

Must PREVAIL! The arrogance of that, and the arrogance to say that MUCH of Europe's wild nature is from open landscapes. Yet again, we have a presumption that agricultural “biodiversity” is the predominant natural diversity because wild herbivores will have kept landscapes predominantly open. This is the “Vera hypothesis”.

The project has now morphed into Rewilding Europe and had its launch in Brussels a couple of weeks ago. However, just prior to the launch, I attended a two-day EC Presidency Conference in Brussels that was ostensibly about wild area restoration across Europe (11). Given a preview of the conference program, I had very real concerns that the sheer weight of emphasis on grazing projects would legitimise what is in effect a cultural convention, predominantly supported in the Netherlands, and which has little or no support in the scientific literature. It just seems to me to be the habitual accommodation of the cultural use of lands as somehow being more naturally biodiverse, and it was given currency by this sentence appended to the agenda item on the presentation about the Rewilding Europe project (12):
“natural management to reconcile maximum biodiversity with wilderness principles”

So, in “reconciling” maximum biodiversity with wilderness principles, isn’t that just compromising those principles? How do wilderness dependant predators like wolf, lynx and bear figure in this "new wildland” because there certainly isn’t any systems thinking evident in the hyperbole of the Rewilding Europe project? Doesn’t it thus undermine the efforts of those that aspire to maintain those wilderness principles? Why isn’t there a demand that these grazing addicts justify their unsupported assertions?

As I expected the conference gave out mixed messages, which always happens when wilderness principles are compromised. I felt in great sympathy with the unease of colleagues from Scandinavian and eastern European countries. I had to agree with Esa Härkönen, the speaker from Metsähallitus, the Finnish nature agency, that there wasn’t much need to restore wilderness in Finland as they already had so much! The eastern Europeans wondered why it was that the first round of sites for the Rewilding Europe project were mainly in eastern Europe, where they too have existing wilderness still in need of protection? But there were also pressures on western European initiatives, such as the restoration of wilderness on ex-military training grounds to the south of Berlin.

New wilderness in Germany

The Foundation for Natural Landscapes in Brandenburg was set up 10 years ago (13). Between 2002 and 2009, the Foundation gradually purchased a total of 10,800ha of land on the former military training grounds of Jüterbog, Heidehof and Lieberose in southern Brandenburg. In addition, the German Society for Nature Conservation (NABU) provided it with 1,050 hectares of land on the former military training ground of Lieberose. The Foundation set out on this land to create areas for the protection of natural processes where nature develops dynamically without or with only little interference by humans. The overall approach is “supporting, experiencing as well as exploring wilderness” (“Wildnis stiften, erleben und erforschen”) so that restoration is being coupled with promoting wider knowledge of wilderness, and the new trails through the areas are to “make its beauty and fascination accessible for the public”

At the 10th anniversary meeting of the Foundation last May, they agreed a wilderness resolution for Germany – the Potsdam Resolution – in which they define wilderness as (14):
“Large, largely unfragmented areas free from human influence and that can therefore develop freely”

One of the goals of the German government’s national strategy on biological diversity from 2007 is to transform 2% of Germany’s territory into wilderness areas by 2020 (15). The restoration of the ex-military training areas is an important contribution towards reaching that goal, and so I was disappointed to hear criticism of the Foundation for not introducing bison as grazers into the protected areas. This seems to me to be the dead hand of dogma reaching out again. Firstly, it ignores the presence of Red deer living free. Secondly, the land of these ex-military ranges needs to recover from centuries of human modification by regaining its three-dimensional structural diversity, enhancing the habitat available for a wider range of organisms beyond the herbivore communities, and with it the return of the ecological functioning of systems such as decomposition processes, nutrient cycling and seed dispersal.

There are reports of sightings of wolf having returned into the region. However, it would be too early to assume that a predator-prey guild would establish if bison were pushed on to the land. Moreover, the natural habitats for the European bison are deciduous and mixed forests in which openings of grassland make up about 20% (16). Thus in the ancient woodland of the Białowieża Forest in Poland, bison primarily forage in moist deciduous forests, browsing as well as grazing so that they find food throughout the vegetative season, but they may also graze in mixed coniferous forests. Bison in the Caucasus region also favour the more open woodland habitat of steppe forest, and they will climb up to alpine grasslands during the summer. However, the training grounds are in lowlands, and so there can be no alpine grasslands in the restoring wilderness. Thus the woodland habitat selection of free living bison strongly supports the need for ecological restoration of the ex-military training areas before it makes sense to introduce them since its depauperate state at present will be an entirely unfamiliar landscape to them.

As it is, the Foundation has a project to develop an ecological corridor through south Brandenburg, linking up their wilderness areas as well as across Germany, but also into Poland by way of the trans-boundary Lower Oder Valley protected areas (17). The aim of the corridor is to improve the migration of wild species like wolf and Red deer. Potentially it would also provide a link into the free-ranging herds of bison that are found in Poland, but also in Lithuania, Belarus, Ukraine, Romania, Russia and Slovakia (16).

Post-glacial ecology

Unlike continental Europe, there were no bison in the post-glacial history of the British Isles (18). Amongst other European herbivores, there were woolly mammoth, Saiga antelope, wild horse, Irish elk (Giant deer) and reindeer, but these animals disappeared from British landscapes, although Saiga antelope and reindeer survived elsewhere in Europe. Of the various evidence put forward for the extinction of the mega (larger) herbivores like the woolly mammoth, the most persuasive comes from a recent modelling of the palaeo-vegetation of northern Eurasia and Alaska. Glacial stage vegetation was open and largely treeless in much of Europe, thus having a high capacity to support large vertebrate herbivore populations. However, the post-glacial warming of the planet coupled with an associated change to a moister climate and with increased levels of carbon dioxide in the atmosphere, resulted in the proliferation of trees and the subsequent decline in grasslands (19). Thus for instance 90% of the geographical range of the woolly mammoth disappeared, with the remaining suitable areas in the mid-Holocene being mainly restricted to Arctic Siberia, which is where the latest records of woolly mammoths have been found in continental Asia (20).

The decline in these large herbivores had knock-on effects for other parts of the food chain, such as the carnivores like the cave lion and cave bear, and would have made them more vulnerable to extinction. With the Irish Elk, evidence from fossil antlers indicates an increasing impoverishment of nutrition, so that it may have been that they were faced with a choice of either good habitat along lowland rivers but increasing hunting pressure from humans, or general absence of humans in a sub-optimal habitat elsewhere (21).

That these mega-herbivores were on the edge as their habitat range declined is indicated in another study based on evidence that comes from data on carnivore dental attrition, and the age structure, life history, tusk growth rates, and stable isotopes from the fossil record of woolly mammoth and mastodon in N. America (22). The authors say that multiple lines of evidence suggest that the large mammalian herbivores of the North American Pleistocene were primarily predator limited and at low densities, and therefore highly susceptible to extinction when humans were added to the predator guild, so triggering a population collapse of large herbivores and their predators. Thus the arrival of humans across the Bering land bridge just tipped them over the edge of the cliff of extinction!

There is doubt that the mega-herbivores of the Pleistocene would have maintained a much more open, savannah-type landscape, and these studies on post-glacial vegetation changes due to climatic factors challenge the theory that human beings were the primary cause of the extinction of the mega-herbivores. We thus owe no duty to assume that our natural landscapes are anomalous in the absence of mega-herbivores because it is not the case that their extinction was the result of an undue influence from early humans. It would seem that the predominance of post-glacial woodland landscapes is what wild nature gave us. Even then, this is continually picked away at by those addicted to open landscapes, and thus our systems analysis must continue.

Aurochs and moose came through the post-glacial changes in vegetation, but in Britain they succumbed to hunting and the advance of agriculture in the Neolithic, becoming extinct about 3,500 years ago (18). Aurochs survived later in Continental Europe, and of course the moose is a free living wild animal in Scandinavia to this day. Thus we did lose at our own hands these two large herbivores from British landscapes. Can we put a measure on their potential influence? Would it have been a sufficient herbivore pressure to satisfy the needs of the arch grazers and their open landscapes?

Estimates for the Mesolithic population of aurochs are 83,896, and for moose of 64,617 (23). Neither of these animals were universally distributed across all landscapes: it is likely that the aurochs favoured wetland and flood plain woodland (3), and I have seen for myself that moose today are found near dwarf-birch, alder and willows scattered around lakes, bogs and streams in woodland openings where they are browsers and not grazers. Compare this with contemporary numbers in Britain of 10 million cattle, 36 million sheep, and somewhere between 600,000 and 1.2 million horses (24) and of course they get everywhere. Do we know whether these numbers of aurochs and moose were significant?

Studies of fossil pollen have long been the basis for trying to understand landscape vegetation cover, but it receives its share of criticism as a reliable measure, even though the critics still have no answer as to why so little blackthorn and hawthorn pollen is found before the Neolithic, which would be the case if there were islands of woodland in an open landscape, and why there is so much elm fossil pollen before the Neolithic when elm is very sensitive to browsing (25).

Fossil pollen studies have moved on in sophistication, and there is a recent paper describing a modelling approach that used vegetation and landscape maps to generate a range of hypothetical pollen assemblages in sedimentary basins (lakes or mires) against which could be tested the effects of changes in vegetation and species composition (26). These were compared to recorded pollen assemblages and it was concluded that the mid-Holocene pollen assemblages observed at Lobsigensee Lake, and at many other Swiss Plateau sites, were likely the result of vegetation cover that consisted of mostly closed beech forests, with the amount of hazel pollen indicating that there were areas of disturbance that led to openness because hazel does not readily flower in closed canopy woodland. The authors believed that their results showed that:
 "the extent of landscape openness as suggested by the Vera hypothesis is too high. Natural (river plains, wetlands, poor soils) and disturbance-induced (floods, windthrow, fire) small openings in closed beech forests were more likely to have produced the observed pollen assemblage at Lobsigensee 6000 years ago"

Fossil insects can also be used as a proxy for understanding vegetation cover. A review and re-analysis of 36 early and mid-Holocene (11,500–4000 year ago) sub-fossil beetle assemblages from Britain looked at the percentage values of tree, open ground and dung beetles (27).The authors say that while they have shown that the Holocene forest was, at times, patchy with openings and a constantly evolving and changing ecosystem due to natural forces – such as such as storms, forest fires or floods - their data did not suggest that open areas were driven by the activities of large herbivore grazing. Thus dung beetles frequencies did not become significant until the Neolithic period, suggesting that grazing animals were not important during earlier phases, or overall lacked influence so that it is undetectable. The dramatic rise of dung beetles in the Neolithic coincided with the arrival and usage of domesticated herbivores. They concluded that:
"the open areas evident within the records were not driven by the activities of grazing animals, that herbivore density does not control natural forest structure, effectively nullifying the crux of the Vera hypothesis"

A counter to the fixation of the conservation industry

Thus to pollen data can be added the beetle data as well as evidence of the indicative distribution of fossil remains of beaver, bear, wolf, aurochs and early domesticated cattle (3) all telling us something about landscapes prior to and after significant human intervention. The increasing complexity being revealed with each new set of data should not be a surprise in itself, but what it doesn't do is be absolutely precise, nor add any particular support for opposing extremes. It does however, maintain a view that the matrix landscape of Britain was woodland and not open space. It allows for the heterogenic nature overall of landscapes prior to large scale human intervention, including areas where trees may have found it hard going, such as above the tree-line or in very wet areas, but also areas of canopied forest in which there were openings created by natural forces or were disturbance-induced. Within that heterogeneity, there would have been openings grazed by the wild herbivores of the time, constantly alert to the fear of predation (28) and where woodland edge and open landscape species would have existed. The wild herbivores would not have been fenced in, in the modern-day deceit of the conservation industry, so entrapping and concentrating their effect, and de-linking them from the behavioural modification of predators. It is therefore clear on present evidence that the openings in the landscape were not created, expanded or necessarily made permanent by wild herbivore grazing.

This an important counter to the fixation of the conservation industry on grazing because the industry never addresses the observations of modern ecology that there must always have been landscape areas that were not grazed. Woodland vascular and cryptogamic (spore bearing) species are damaged by trampling and grazing, and do not colonise new woodland very easily. Thus it is hard to see how they could have a distribution in the ancient woodland of today if they had only existed in very isolated refuge in such as small areas of woodland on ledges or steep ground. It is also very hard to think of genetically viable meta-populations of woodland plants existing in the discontinuous, patchy landscapes of the Vera hypothesis (29). As an example, it would be impossible for species like toothwort (Lathrea squamaria) a parasite on the roots of trees like hazel and alder.

I give also the example of the barn owl, which is not immediately obvious in this context because it is not a woodland bird other than it does nest in tree hollows, but also in rock crevices. A recent news report claimed that three-quarters of British barn owls live in man-made nest boxes suggesting that these owls are now largely reliant on such measures (30). However, the provision of artificial nesting sites is not the key factor for barn owls and can be harmful (see later) if there is not also suitable hunting habitat nearby. That habitat is the long, tussocky rough grass that exists in ungrazed land where small mammals like field voles thrive (31). Tony Warburton, president of the World Owl Trust based in Cumbria says that in many areas where barn owls used to be a common sight, their foraging habitat has disappeared (30):
"Ungrazed, unmown grassland has gone. It's not going, it's gone. The deceptively beautiful green Cumbrian hillsides are heavily grazed. They are just green deserts. Field voles can't live there"

The Barn Owl Trust believes starvation is the major cause of mortality for barn owls, with road deaths coming a close second (32). The latter is not surprising if you consider that unfortunately roadside verges probably offer the only ungrazed habitat in many locations. Thus the Trust say that rough grassland with a deep litter layer is by far the most important thing for wild barn owl conservation because lack of food (mainly field voles, wood mice, and common shrews) is the biggest factor limiting population recovery. In a painful irony, the Trust point out that the wide variety of options in the Higher Level Stewardship scheme are of little or no benefit to barn owls. But then of course, we know that Higher Level Stewardship is being used as the driver by Natural England to ensure that every landscape in England is grazed.

Mark Fisher 2 December 2010, 6 December 2010

(1) Natural England relaxes rules on supplementary feeding to help livestock farmers in AE schemes through the big freeze, Natural England Press release 4 December 2010

(2) The craze for conservation grazing, Self-willed land May 2009

(3) Open or closed – what is the natural landscape matrix of a wild Britain? Self-willed land June 2009

(4) Stop Fencing the Malvern Hills!

(5) Electric Fencing on the Malvern Hills – an Introduction

(6) Scenic surrounds transformed, Malvern Gazette 22 November 2010

(7) Fences reduce water pollution, Tom Marshall, Planet Earth 20 October 2010

(8) Peterken, G. F. (2000) Rebuilding Networks of Forest Habitats in Lowland England, Landscape Research, 25: 291-303

(9) Wild Europe, Self-willed land

(10) Wilderness is more than forest alone, Rewilding Europe (webpage no longer there)

(11) EC Presidency Conference on wild area restoration, Wild Europe Initiative

(12) “Rebuilding the Natural Heart of Europe EC Presidency Conference on Restoration of Large Wild Areas

(13) Foundation for Natural Landscapes in Brandenburg

(14) Potsdamer Resolution Wildnis Mai 2010 (Potsdam Resolution on wilderness May 2010)

(15) National Strategy on Biological Diversity, Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, October 2007

(16) Pucek, Z. 2004. European Bison. Status survey and Conservation Action Plan. IUCN/SSC Bison Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.

(17) Der Ökologische Korridor Südbrandenburg (The Ecological Corridor South Brandenburg), Stiftung Naturlandschaften Brandenburg

(18) A History of British Mammals, Derek W. Yalden, Mammal Society

(19) Allen et al (2010) Last glacial vegetation of northern Eurasia, Quaternary Science Reviews 29: 2604-2618

(20) Nogués-Bravo et al (2008) Climate Change, Humans, and the Extinction of the Woolly Mammoth. PLoS Biol. 2008 April; 6(4): e79.

(21) Stuart et al (2004) Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth. Nature 431: 684-689

(22) Ripple and Van Valkenburgh (2010) Linking Top-down Forces to the Pleistocene Megafaunal Extinctions. BioScience 60: 516-526

(23) Maroo,S. and Yalden. D.W. (2000) The Mesolithic mammal fauna of Great Britain. Mammal Review 30:243-248

(24) Want to know more about our animals in the UK? DEFRA

(25) Rackham, O. (2006) Woodlands. HarperCollins ISBN 0007202431

(26) Soepboer and Lotter (2009) Estimating past vegetation openness using pollen–vegetation relationships: A modelling approach. Review of Palaeobotany and Palynology 153: 102–107

(27) Whitehouse and Smith (2010). How fragmented was the British Holocene wildwood? Perspectives on the ''Vera'' grazing debate from the fossil beetle record, Quaternary Science Reviews 29: 539–553

(28) Laundré et al (2010) The Landscape of Fear: Ecological Implications of Being Afraid. The Open Ecology Journal 3:1-7

(29) Thomas and Packham (2007) Ecology of Woodlands and Forests: Description, Dynamics and Diversity. Cambridge University Press ISBN 978-0-521-54231

(30) British barn owls 'depend on humans' , Victoria Gill, BBC News 25 November 2010

(31) Optimum habitat in Britain, The Barn Owl Trust

(32) Causes of mortality, The Barn Owl Trust