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Large carnivores as the focal species for reinstatement of natural processes in Britain |
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Seeing a fox is not yet a totally uncommon event, given the persecution they suffer, but seeing one that is in its own domain certainly is. I startled a fox on a coastal slope in Pembrokeshire, and watched in awe as it scurried along a trail at the base of the rock face that edged the slope, and then negotiated with astonishing ease that seemingly sheer rock, turning at its summit to throw me one glance before descending onto the next slope area where it knew I could not follow. I’ve noticed before the tunnels through the wind-pruned scrub of blackthorn and bramble cascading down the slopes from the cliff tops, once seeing a fox dive into one from the coastal path. That the fox I saw this time was at home in these larger, inaccessible, slope areas that seem like stable land slips, implies an ecosystem in microcosm, a place where each trophic level is occupied and the fox has everything it needs. The raptors I also saw that day add to that impression, peregrine falcons cruising the cliff faces for rock pipit, kestrels hovering over the maritime grass and scrub in search of small mammals. These are the natural processes so missing in our wider landscapes, as are the components that bring life to them – the focal species (1). Kids in a candy shop I wonder if others, when they bring themselves to contemplate the restoration of these components, actually understand the ecological implications, or whether the depth of their understanding is just of a restocking of the landscape zoo, but only if the returnees can be confined and well behaved, so that they don’t inconvenience us. I got this impression from yet another panel discussion on “rewilding”, held a few weeks ago in London, the event framed around the extirpation of the large carnivores, the wolf, bear and lynx, and the need to “redress the balance and bring these captivating creatures back” (2). Despite my awe at witnessing the natural world, I don’t think I would put those two words together to describe a wild animal, but then I wouldn’t have put together the particular panel that the Earthwatch Institute had done. I have myself declined such a situation that I thought more sought controversy than understanding and, sure enough, my informant at the event reported a low commitment amongst panellists, with a skewed focus on potential hazards necessitating control and management to prevent alleged damaging consequences. It was ever thus in the suffocation of our small minded island, immune to the inconsistencies in this negative approach when compared to the reality of our neighbouring countries. Thus did we see the Dutch and the Danish wring their hands in concern that their landscapes have been transformed past the point where they can support the return of wolves (3) the almost obligatory excuse that is hidden behind here? Then there was the stunning arrogance of the bigoted farming representative on the panel in accusing those seeking reinstatement of species as acting irresponsibly, the species that let us remember suffered extirpation because of his predecessors persecution. He described them as behaving like “kids in a candy shop”, accusing them of wanting everything now in the return of these species. Would this bonehead ever see past his own vested interest? I don’t think I would waste time on him. Making a breakthrough in creating dynamic policy change means moving past inhibiting barriers like him to a wider set of participants, to expert communities with greater intellectual reach on which to build support before eventually returning to that bigot, but with a momentum generated. But who will take the lead on this? Who will make the ecological case for reinstatement, visioning a Britain where these species have their place, and undertake the process of civil engagement, as did the Netherlands and Denmark over the return of the wolf? A fascinating insight into contemporary trophic function As I find is often the case, a comment from a seemingly unattached observer under the announcement of the Earthwatch Institute event had more of valuable interest than the event itself, encapsulating in just one paragraph a fascinating insight into contemporary trophic function (2). Peter Forward, who I discover is a self-described “artist of sorts” and wildlife volunteer in Melbourne, Australia (4) contrasted the situation in his homeland, where the top native carnivore has also been lost, only to have been replaced by a domestic dog that went wild, along later with introduced predators like the fox and cat. He notes that predation by feral cat and fox, coupled with human habitat destruction, is sending Australia’s unique mammals towards extinction. Peter highlights the persecution of bilbies, a desert-dwelling marsupial omnivore, with only 200 now remaining in the wild (5,6). He could also have pointed to the loss of quolls, nocturnal carnivorous marsupials, also endangered through predation by feral foxes and cats (7).Then he makes an interesting observation, that the feral cats and foxes avoid dingo habitat, which is unsurprising given that both cats and foxes are hunted and killed by dingoes (8,9) the fear induced in them modifying their behaviour and causing their spatial redistribution (10,11,12). These current interactions between carnivores should be put into the context of the original native fauna of Australia. The dingo is a free-ranging wild dog that has been present in Australia for at least 3,000 – 5,000 years. Whether it arrived on the continent unassisted is unknown, but its likely origin is descent from East Asian domestic dogs (13). The 3,000 years of isolation before other canids landed in Australia (also as domestic animals) allowed the dingo to assert itself as a species (14) and it certainly arrived many millennia before foxes and cats went feral there in the nineteenth century (15, 16). The arrival of the dingo was, however, followed within a millennia by the loss of the now extinct marsupial carnivore, the thylacine, from mainland Australia, thus eliminating the continents original top carnivore of the Holocene. The suggestion is that the dingo drove it off because of overlapping niches between the two predators in competition for prey, and which would explain why the thylacine persisted through to the twentieth century in dingo-free Tasmania. While they may have shared some of the same prey, the two carnivores utilised different predatory modes, the thylacine considered to have the same approach as large felids, of ambushing its prey, whereas dingoes are pursuit predators like wolves, their social behaviour based on settled packs (17). In the killing stakes, however, relative size is often important. Thus dingoes have been shown to be similar in size to the male thylacine, based on Holocene fossil specimens, but considerably larger than female thylacines (18). It is possible that as well as the pressure of niche overlap, the direct killing of female thylacine by dingoes, as a response to competition for prey, could have depressed the reproductive output of this species, driving it to extinction on the mainland. The killing and possible eating of potential competitors is common amongst mammalian carnivores, and is called Intraguild Predation or Interspecific Killing (19) and so not only did the dingo take over the ecological role as top predator from the thylacine, it also responded to the later arrival of foxes and cats by controlling these mesopredators, the second-tier carnivores (20). The presence of dingoes modifies the behaviour of cattle
It is then that Peter lays out an ecological
cascade that perhaps is beginning to become apparent, even in the cultural
landscapes of Australia. In a parallel to the array of changes seen in
Yellowstone National Park after reinstatement of the wolf in 1995, their
effect seen on the distribution and size of the elk population and
consequently on landscape vegetation (21) Peter describes the affect that
dingoes have on what is probably the largest herbivore after the feral
camel in the Australian landscape (2): Here Peter is describing a trophic cascade, where the presence of dingoes modifies the behaviour of cattle (it is probably only calves that are at threat of predation by dingoes) which in turn releases the vegetation from grazing pressure, the resulting changes in vegetation providing a greater array of habitat niches that encouraged other species to return. I could not find Peter’s description of this interchange between cattle and dingoes in the literature, but instead I got a sense that there is a gap in published evidence about changes in vegetation in response to changes in dingoes. The lack of study of the positive effects of dingoes is perhaps a result of the ambiguity of their status, which although its conservation status is regarded as “vulnerable”, has no listing in federal legislation (22). Moreover while it is protected by legislation in some Australian states (in the Northern Territory as native wildlife, in Australian Capital Territory, and in the protected areas in Queensland and New South Wales) it is a ‘declared’ pest throughout much of its remaining range, with landholders being obliged to manage populations, and for which poisoned baits are used. Even so, I did find two studies that related the effect of changes in herbivory by kangaroos and their predation by dingoes. In a study on pastoral stations in the arid zone with and without dingo control, there were strong positive correlations of dingo activity with the abundance of small and medium-sized mammals, and strong negative correlations with kangaroos (23). Those sites with more stable dingo packs had more plant cover and diversity. Another study showed that undergrowth vegetation in forested National Parks in New South Wales was reduced by an increase in numbers of wallabies and kangaroos in areas where dingo numbers had been reduced by poisoning (24). In combination with this reduction in density of understorey vegetation, the number of smaller, native mammals, such as ground dwelling rodents and small marsupials, declined as well, because it is where these mammals lived. Since predation by feral foxes is one of the most important threats to these small native mammals, the grazing by the large herbivores – the kangaroo and the wallaby - had the effect of reducing preferred habitats for shelter and refuge during the day, leaving them exposed to predators. The cascading effects of dingoes through Intraguild Predation and behavioural modification of mesopredators, and the behavioural modification and predation of herbivores, ripple through the trophic levels, confirming their keystone role as a top predator. If the prejudice against them is removed, and thus their persecution, then dingoes can facilitate the conservation of native small mammal species against the threats from feral foxes and cats (25). Intraguild Predation and suppression of herbivore pressure at many scales are key ecological cascades that are missing from Britain because of the absence of large carnivores. I am always looking for evidence of ecological cascades when out walking, after having noticed the interplay between foxes, feral cats and rabbits and their effect on vegetation in the limestone of the Yorkshire Dales (26). The recent observations I note above of predators on the Pembrokeshire coastal cliffs add to that search and confirmation of that fundamental role in natural processes. And yet the usual limited horizons and the inability to shake off stolid preconceptions really plague British thought about reinstating more of those natural processes. It is patently obvious that our statutory agencies have no interest in developing the evidence base here for any ecologically necessary reinstatements. Instead, as we so often see, the panacea here for natural processes is the unrestrained herbivory of domestic livestock. The suppressive effect of the cattle grazing
For a number of years, I have accompanied
final year Geography students on a residential field class to the
Ennerdale Valley in the Lake District (27). You may have heard of this
valley as “Wild Ennedale”, and it has the distinction of being the most
over-promoted, but critically unscrutinised “restoration” project in
England. It was held up yet again as an exemplar recently in the puff
piece in the Observer about “rewilding” Britain (28):
And yet as I explained in a comment to that
article, it hasn't seen those conifers replaced (28): While I was never comfortable with the initial introduction of cattle grazing in 2006, subsidised from 2009 by an unknown amount of agri-environment funding, I was reconciled to it on the basis that it was only on a couple of areas of clearfell in a valley large enough to contain a variety of approaches to restructuring and decommissioning a forest plantation (29). It also gave the students project opportunities to characterise the suppressive effect of the cattle grazing, measuring the attenuated growth of the very few heavily chewed native trees that struggled to establish outside of the exclosures. An initial study in 2010 found the height of native tree regeneration outside of the exclosures was related to the slope of the land and thus its accessibility to cattle grazing (29). The greatest level of attenuation was on the clearfelled flat land at the base of the slope where the cattle spent 40% of their time. Cattle were able to gain access to the upslope flat areas along easy routes with gradual incline, including an existing footpath within the grazing compartment. However, young trees on sharp inclines were not browsed or browsed less. Of course, if the domestic livestock had been sheep, then this distinction due to slope would not exist. A second study using transects confirmed the effect of accessibility, as constrained by slope and the exclosures, on the height of tree species, but also threw up the difference in diversity of trees species developing inside and outside of the exclosures (29). Native species predominated within the exclosures, whereas the reverse was true outside, where the plantation conifer species of larch and Sitka spruce were the only trees along the transect on flatter land, and dominated along the transect up a slope. This difference in species is a result of the greater palatability of the native species to cattle, compared to the plantation conifers – they heavily browse the former but not the latter. In effect, cattle grazing will thus return these clearfell areas back to the state they were before deforestation of the conifers. The cattle grazing is thus a pointless approach on which over a million pounds is being wasted.
In discussion, the students recognised that
the lack of a constraint on the cattle grazing would drive the landscape
in only one direction, making the connection that in natural systems that
constraint would be provided by top carnivores – or by a fence, as was
shown by the exclosures! The project partnership though has made great
play wherever they could of the spectacle of the Galloway cattle, and of
their alleged ecological benefit, in what was still some way from being an
entirely agricultural landscape (30): Forest and farmland rather gives the game away about what was really the aim at Ennerdale! Before I get on to that, I found out that I was not the only one to have revolted against these domestic livestock ludicrously being equated to a keystone wild animal, extirpated from these shores. A couple of young men walking their dog in the valley in 2008 pulled off a remarkable parody of that absurdity by recording a video of themselves making the important discovery of coming across these bears, indicating that they could make some money out of this discovery, and wasn’t it odd that these bears looked a bit like cattle (31)? Cattle grazing spread further into the valley Returning year on year with the students, it just seemed to me that the boundaries that delimited the cattle grazing became more fuzzy, and spread it further into areas where their impact was less obvious because tree regeneration had started two decades earlier when sheep had been removed from alongside the river. However, what was rarely acknowledged openly was that roe deer were being controlled by a Wildlife Ranger employed by the Forestry Commission (32). The valley has around 80 to 100, of which 20 are shot annually, ostensibly so that their browsing does not prevent woodland development. If that was the concern, why were the cattle introduced? Why are native animals being sacrificed on the back of this cattle grazing dogma that is patently more responsible for holding back native tree regeneration? The greater subterfuge was not to disclose last year another phase of agri-environment funded expansion of cattle grazing so that it now penetrates throughout the valley. I had to stumble over this additional £872,780 agri-environment subsidy by myself, and which has been the catalyst for re-evaluating whether the valley would any longer have any value for the student field trip. As it was, the course had started, and so we were committed to another visit, but the students were forewarned in the lecture series that preceded the field trip (29) and one of them undertook to obtain the agri-environment agreements through a Freedom of Information request (AG00344307 and AG00478850) and use them in his project work. On the day of arrival in late April, I couldn’t even face walking around Ennerdale on my own, which is what I usually do on the first afternoon to avoid the propaganda talk about the benefits of the cattle grazing that the students get. You can only so often hear of the need for the cattle to break up the ground so that it aids trees seeding in, when this person is standing next to an exclosure that is rammed with native tree regeneration that has happened in the absence of cattle, and what native trees you do see outside the exclosures are doing dreadfully. Instead, I drove over to St Bees Head, about 13 miles away on the coast, to walk at low tide over the rocks below the cliff. I saw cormorants doing their usual thing of hugging the coast as they flew northward. The white of sea campion and the pink of thrift could be seen flowering in the maritime grass on the cliff slopes. It was great fun and lifted my spirits. The next day, as the students got on with their projects, I went up Low Beck, a tributary to the River Liza in Ennerdale valley, to see the water cascades in the fabulous rocky gorge, and which is also a refuge for native trees and woodland wildflowers, a rare gem in a sea of surrounding rubbish that is not now going to improve. I’m not going back to Ennerdale ever again. Cattle are now all over the place, the result of a complete paucity of imagination. I’m dying inside every time I consider the lost opportunities. It makes me so mad. When we asked the students at the end of our stay how they would score the valley for wildness, they gave it a three out of ten! Given that resounding lack of endorsement, we have now scouted other locations for the field trip, and which I will write about later. Positive ecological relationships associated with top carnivores That Ennerdale could be so different is glimpsed from the positive ecological relationships associated with top carnivores in Europe. In areas where there is an absence of large carnivores, the numbers of wild herbivores, especially different deer species, have greatly increased in the modified landscapes of human use. The impact of increased herbivore pressure has affected ecosystems through reducing tree regeneration and tree species, the diversity of herbaceous vegetation, as well as decreasing songbird diversity (33,34). The negative effect of herbivores adds to the evidence from many studies that have demonstrated the effects of ungulate browsing on species composition, nutrient cycling, and on the entire successional pathways of vegetation communities. Since top predators may in turn exert a strong influence on lower trophic levels, then they too function as system directing species (35). In addition, multiple predator effects on prey species and on ecosystems can be synergistic, the limiting effect of two co-occurring species of predators being stronger than that exerted by one species. Thus the densities of roe deer across Europe were found to be significantly lower in areas that had both wolf and lynx compared to areas with wolf alone, or areas without either predator (36). The presence of bear alone appears to be insufficient to prevent a break out in cervid populations (deer and moose) in northern European forest ecosystems, whereas the combination of wolf and bear predation, with or without human hunting, maintains cervid densities lower than without wolf and bear (37). There is evidence that the structuring force of top predators through trophic cascades promotes species diversity, or is spatio-temporally associated with it. At its simplest level, this could be due to top predators making available resources essential to other species that are otherwise unavailable, or scarcely available, such as carrion, a high quality detritus composed of dead animal material (38) or enhancing survival through suppression of mesopredators (39,40). Perhaps the key factor though is that top predators usually need large, relatively undisturbed areas for foraging and breeding (41) and these areas can be expected to encompass the needs of many less demanding species. Evidence for this species diversity comes from reports of a spatial occurrence between five raptor species that differ widely in their diet and habitat associations - goshawk (Accipiter gentilis), pygmy owl (Glaucidium passerinum), Tengmalm's owl (Aegolius funereus), tawny owl (Strix aluco) and scops owl (Otus scops) – with greater diversity of avian species, vulnerable avian species, butterfly species and tree species at various locations in the Italian Alps (42). The alpine and forested landscapes of the Carpathian Mountains in Romania afford an example for synergy between mammalian predators, and where the presence of at least one or more of wolf, bear or lynx, was co-located with 55% of the birds and 80% of the mammals of national significance for Romania (43). In reality, two thirds of the areas of occurrence in this study had the presence of all three carnivores. The importance of the presence of the larger carnivores in contributing to and regulating natural processes worldwide is increasingly recognised: areas with the highest number of predator species and with intact large carnivore guilds are likely to be indicative of locations for exploring and conserving wilderness qualities. Compared to historical times, the contraction of the range of large carnivores has been the most extensive in Europe (44). However, the contemporary overlap of large carnivore ranges shows the distribution of a three-species guild of wolf, lynx, and bear – our original top predators – that stretches from eastern Russia to Scandinavia and the edges of central Europe, and including Finland, Sweden, the Baltic states, the Balkan states, and the Carpathian and Dinaric countries. It is in the behaviour of the large, free-living, wild mammals to have large territories or home ranges based on their feeding requirements, social characteristics and dispersal tendencies. The space available to these species to live freely and undisturbed substantially diminished as the extent of human habitation and landscape modification in Europe progressed. The home range sizes of individual large carnivores in Europe vary between 100 and 1,000 km2 – depending on habitat characteristics and environmental productivity (41). This implies that they never reach very high densities – typically ranging from 0.1 to 3 per 100 km2. In addition to these characteristics of resident, adult individuals, juvenile large carnivores often range widely during their dispersal phase, with some individuals moving over hundreds of kilometres. Wolves have the widest distribution among the large carnivores in Europe, with the nearest substantial populations to us being in Italy and Spain, although they are also present in France (45). They are gradually moving west across Europe, having established in Germany from Poland, and moved from there into Denmark, the Netherlands and perhaps Belgium. The wilderness dependency of wolves will always be contested because of their great ability for dispersal through hostile terrain, and their seeming adaptability to habitat conditions and human presence. Wolf habitat has been described as everywhere where humans do not kill the species and where there is something to eat. However, this is a function of their very nature, as territoriality, social behaviour and dispersal are the intrinsic mechanisms regulating wolf density. There is every reason to believe that areas recovering some wilderness qualities after removal of human influence do recover a wolf population. There is always the claim that wolves are a risk to livestock. However, while wolves are now establishing territories in areas that have less claim to wilderness qualities, they still seek out aspects of wild nature, as revealed by their dietary preference. They don’t like eating sheep, as neither do lynx. Wild ungulates make up 94-96% of the diet of wolves in Central and Western Poland (46) and Germany (47) and 89% -95% of the diet of wolves in the Alpine, Apennine and Mediterranean ecosystems of Italy (48). Roe deer are the primary food of lynx, with other wild species making up over 98% of their diet in the Jura (49) and Dinaric Mountains (50). Even where roe deer densities are low, lynx still seek out roe deer in preference to domestic livestock (51). Lynx also take red fox (49,52) a mesopredator that is persecuted in cultural landscapes as a pest species (53). What is there to fear?
James Mackinnon nailed it when he wrote that
it wasn’t fear for our lives that led to the destruction of
"man-eating" beasts around the world (54). Instead it was an
accumulating loss as we invaded and destroyed their habitat, and
slaughtered their prey, subsequently slaughtering them in protection of
the livestock with which we replaced their prey. Now, with our top
predators long gone, he believes it is a fear of
the unknown that
clouds our judgement about reinstatement: I think he is right on all counts - it was not fear of wolves, but vested interest in protecting livestock. The demonising of wolves had more tangible origins than things like the “Little Red Riding Hood” stories and the fears of being attacked. One such formative era in attitudes to the wolf was when it posed a threat to the systemised exploitation of land brought in by the Norman Conquest after their wholesale expropriation of land (55). In this massive intrusion of more intensive land use into a much greater area, a disturbance that brought humans into greater conflict with wildlife remaining in the remoter areas, the Norman governing classes imported the concept of hunting forests with them, and the non-native fallow deer with which to stock them. These forests had few trees, the word forest coming from the Latin for door (fores) so that forestis meant “outside of” – in this case, outside of common law. Instead, forest law applied, which was that which reserved all rights and resources to the Normans, providing penalties against ordinary people who transgressed by taking their deer. The Normans also brought with them Abbeys, providing their favoured monks with new estates and endowments. Wolves were obviously a threat to their deer hunting, as they were also to the organised sheep grazing of the Abbeys, who made fortunes selling wool in Europe. In the early 13th century, Gilbert son of Robert de Gant, Earl of Lincoln, granted rights to Rievaulx Abbey for pasture in one of his hunting forest areas in Swaledale, as well as sheep-folds and lodges, and the right of keeping hounds and horns. (56) The abbey also received permission to catch wolves “in any way they could”. As Richard Muir has written, wolves were present in the less intensively worked and settled fringes during the Middle Ages, but instances of attacks on humans by wolves appear to have been very unusual (57). Medieval records contain various references to bounties being offered for the slaughter of wolves, particularly by the Cistercian Abbeys like Rievaulx, but as Muir concludes, this does not reveal that wolves presented a threat to human life, but instead that they were a threat to the monastic flocks of sheep. As wildlife in general dwindled from expansion of farming and continued hunting, then the conflicts from increasing competition would have added to demonise wolves amongst the general populace, leading to intensified persecution. It is thus possible, that the methods of farmers living with wolves that evolved in continental Europe, and which has and is ensuring a presence there (41) were never learnt by ordinary people here, as it was pre-empted by the extermination approach of the deer forests and abbeys. That fear of the unknown has to be conquered by rational thought through an understanding of the ecology of wild nature. Trophic function is a key element of ecology, and we must prepare ourselves for its reinstatement by understanding the requirement for the return of key species. The curse in the reinstatement of former native species is that we are an island, which precludes the natural dispersal of species - unless they can fly across or swim the English Channel. It is no wonder that the frustration at the poor aspiration for reinstating these species results in people taking their own action, as may have been the case with the Devon beavers (58). Surely we should be expecting this action from our own statutory nature agencies, supported by Government? Since I don’t expect that to happen any time soon, we will have to make the case ourselves. Mark Fisher 8 November 2014 (1) Lambeck, R.J. (1997) Focal Species: A Multi-Species Umbrella for Nature Conservation. Conservation Biology 11: 849–856 http://flash.lakeheadu.ca/~rrempel/ecology/Biodiversity_Papers/PDF0242-Lambeck.pdf (2) Rewilding the UK: Living in the Past or Preparing for the Future? 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