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Movement ecology and rewilding |
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It may seem that I endlessly try to demolish the nonsense of the herbivorvist REFARMERS, but their denial of movement ecology as well as trophic ecology is the very foolish or wilful blind spot that really trips them up. This article is a contribution to a rewilding themed issue of ECOS that is coming out later this year. Given how fashionable it has become, it was a surprise to see that a highly funded restoration scheme in the Scottish Highlands sought to disavow that it was a rewilding project (1). It perhaps wished to confront any confusion about its aims, when the scheme – Cairngorms Connect – had received its funding from the same source as Rewilding Britain’s Summit to Sea (2). The Highlands scheme said that it was currently unwilling to commit to the reintroduction of large predators, which it believed had until recently been implied by rewilding (1). It went on to say that rewilding is being redefined in Britain, noting that a focus instead on restoration of habitats and natural processes was in alignment with the use of the term more widely in Europe. Others will be comment on these two funded schemes elsewhere, but I want to take issue with this redefinition. A manifesto for rewilding the UK I thought I had bottomed what it meant in a manifesto for rewilding the UK that I circulated in 2003 (3) parts of which were republished the following year in ECOS (4). The Wildlands Project (TWP) in America, and its periodical Wild Earth, had been the originators of rewilding and were the inspiration for the manifesto. I paraphrased from the TWP webpage on Mission, Vision and Purpose to give a flavour of the central aim of establishing a connected system of wildlands to stem the loss of wildlife (5). It would be a natural recovery of whole ecosystems in every region of North America over a period of 100 years and more in an approach that ensured that they are all connected in one continuous wildlife corridor. Areas designated for rewilding would be of sufficient size to support viable, self-reproducing populations of all native species, including large predators, and will express the natural patterns of diversity at the genetic, species, ecosystem, and landscape levels. I noted for the UK that we would look for an inflow of species as recovery evolves, that wild mammals would return to participate in shaping the rewilding. In turn, we shall probably need to reintroduce predators so that our wild spaces are supplied with a full complement of its essential tools for balance. Even back then, I knew that large carnivore conservation wasn’t the purpose of rewilding, as implied by Cairngorms Connect, that instead the repatriation of top predators would be essential for what I now term as trophic ecology, the interaction between all trophic levels in a wild ecosystem. So what is this redefinition of rewilding that is more widely used in Europe? Two recent articles in the literature on the habitat and diet selection of large herbivores at two differing locations are illustrative, both claiming to be studies of rewilding, and involving European bison (Bison bonasus) and primitive horses to restore and maintain open landscapes: the secondary-reforesting heathland site of Döberitzer Heide, is an ex-military training area close to Berlin in Germany (6); and the shrubby coastal dune site of the Kraansvlak is in the Netherlands between IJmuiden and Zandvoort (7). The other thing that these two sites have in common is that they are both fenced to contain the grazing animals. Consider what that means to the animals enclosed therein: the choices on habitat heterogeneity in which they were to exist were made for them; there would be no ability to migrate if their instincts led them to seek other selections; and there would be no exposure to natural predation. This is the hallmark of species domestication (8). It cuts across the life history strategies of wild species, as a simple calculation will demonstrate, but first some explanation. The use of space by wild animals such as herbivores is determined by the interaction between their movement and their use of resources, and is thus mediated by habitat selection, the biotic interactions that include behavioural modification and predation, seasonality, and the intrinsic factors of the moving individuals, such as social group size and social group composition. An animal’s decision to move is a response to the need to satisfy its requirements for resource use (or refuge) a change in location potentially offering up better or untapped resources (9-12). Animals can increase their use of a high quality resource area by increasing the duration of their visit and/or the frequency of revisits after allowing for regrowth. These processes ultimately determine home range size, a geographic area that is very roughly related to mammal size and thus energy intake. Study of free-living bison, found only in a few European countries (Belarus, Lithuania, Poland, Romania, Russian Federation, Slovakia and Ukraine (13)) has shown that it is a gregarious animal, whose daily activity rhythm is active feeding during movement (60% of the day) alternating with resting spent mostly on rumination (30%) and the remainder (10%) on roaming without feeding (14). The central part of their home ranges are the most intensively used, which in the season of vegetation growth vary from 80–150 km2. Given that these ranges are not defended and overlap greatly, then the estimate is that an area of 200 km2 would accommodate a population of 50–70 bison, which I will take as a population density of 0.003 per hectare. Fences bust through habitat selection and home ranges If rewilding is the restoration of natural systems, then you might expect that the approach of these two projects would be to exemplify the principle understandings of movement ecology and trophic ecology, like the geographic and environmental requirements of home range for free-living species. However, the fenced area of 1,860ha of Döberitzer Heide encloses 80 bison, giving a population density of 0.043 per hectare, an order of magnitude (x14) more than would be seen with free-living bison. Similarly, the population density of 0.073 per hectare of the 16 bison enclosed in the fenced area of 222ha of the Kraansvlak is even greater than that (x24). Consider also that both locations enclose horses along with the bison, 24 at Döberitzer Heide (plus 90 red deer) and 14 at the Kraansvlak, then the herbivore pressure within those enclosures far exceeds the bounds of what may exist in natural systems, risking the possibility of coming up against resource limitation, but the herbivores being prevented from moving in mitigation. In a framework of assessment of the wildness of large vertebrate populations under various management constraints, the busting of home range requirements, the block on migration, and the absence of predation, would result in a very low wildness score for the bison at Döberitzer Heide and the Kraansvlak (15). That constellation of impositions through human agency should be familiar to you, as it was the regime that led to the discredited fiasco at the Oostvaardersplassen and its inevitable termination as a failure (16-19). Reclaimed in the late 1960s from the Ijsselmeer, the lake between North Holland and Friesland in the Netherlands, this location became emblematic for the Dutch concept of nature development, of maintaining conservation reliant species in an open landscape with enfenced herbivores, but many labelled it as rewilding. At their historic peak of summer population, the fenced area of 1,880ha entrapped up to 500 Heck cattle, 1,000 Konick horses and 2,500 Red deer (16,20). Unsurprisingly, I can’t find home ranges for cattle and horses, as they are not free-living, wild species, but the home range for Red deer (Cervus elaphus) is in the order of 2.7 km2 but with a population density of 0.15 per hectare in recognition of the groups they form (21). Even so, the population density of Red deer in the Oostvaardersplassen at its peak of 1.33 per hectare is nearly nine-fold higher than would be found if they were free living. Add in the impact of the cattle and horses as well, then the cause of the winter starvation and death of so many animals at the Oostvaardersplassen is explicable by the total herbivore population massively exceeding food-limited carrying capacity, the devastating consequences being meted out in degradation of landscape vegetation so that no shrubs or trees remain. This is overgrazing, an excess of herbivory that led to degradation of plant and soil resources, demonstrating that herbivore numbers at food-limited carrying capacity damage ecosystems. It is an aberration that occurs in wild nature when large carnivores are extirpated through human agency (22). An absence of ecological understanding Arguably, the Oostvaardersplassen is the progenitor that spawned any number of these ecologically illiterate rewilding projects predicated on enfenced herbivores in Europe (including in the UK) that ignore the life history strategies of wild species, or make no attempt at extrapolation for the domesticated species, as much as it has led to a spurious and unnecessary redefinition of the term, albeit without being honest about its reliance on fencing. It’s not hard to conclude that fencing is an acknowledgement that we are failing to successfully coexist with and conserve wild nature, but more importantly, fencing creates a spatial restraint that is likely to lead to the biological needs of animals not being met, and which ties us to an intervention for population regulation and limitation – a containment and illusions of control. Fencing also cuts across the natural instincts for habitat selection of truly wild animals, introducing synthetic edge effects that adversely alter vegetative processes. It raises the issue of whether the true natural habitat selection preferences - the life-history requirement of the needs to acquire food and water, find mates, rear offspring, defend limited resources and avoid predators - can ever be expressed by the domesticated animals used in these rewilding projects, long selected and bred as they have been to suit the habitat conditions and simpler needs under which we want to maintain them (8). It is important to note this domestication leads to forms of a wild ancestor species that have decreased brain size, a process that is not reversed by feralization (de-domestication) over many generations (23). Thus domestic forms cannot lead to natural conditions, but only to an artificial biodiversity (24). Above all, this absence of ecological understanding demonstrates a complete lack of commitment to connectivity, blocked as it is by the fencing. It is, however, an absolutely essential characteristic of the original evolution of the meaning of rewilding that I recognised 16 years ago, and which often eludes contemporary exponents of rewilding (eg. 25-28). Even more galling is that the current criticism of rewilding - that it is ill-defined so that it has become a plastic term that encompasses anything and everything - is based on that contemporary exposition, rather than on the original evolution of the meaning (29-34). Indicative of that is the paucity, if any, of back referencing to its origins, with frequently only just one article cited - that by Soulé and Noss published in Wild Earth in 1998 (35). The article is never referenced with the correct volume, issue and page numbers, indicating an ignorance of its context, as it is an ignorance of what led up to the article, and what came afterwards in the further evolution of the term by TWP. All that information is available, as I have been able to show, and so it is either a wilful ignorance or a woeful lack of scholarship. A science-based design-led approach I have traced the early evolution of rewilding from when it first appeared in print in 1990, through the publication span of Wild Earth from 1991 to 2004 where the TWP and other conservation activists shaped and evolved its meaning by reporting on their activities, and that last year being when Dave Foreman, a central character in the evolution of meaning, drew its conceptual foundations and actions together in his book on rewilding North America (36). It is a history of a shared concern for recovery and conservation of wild nature that led a number of conservation biology’s most important thinkers to develop ties and become engaged with radical environmentalism, a new activism of the late 1980s. The object of TWP and Wild Earth was to help translate the theories and information of the science of conservation biology into grassroots preservation activism, to help all groups and individuals working to protect biological diversity. A key lesson for me is that cross fertilization between the conservation biologists, who brought with them the latest conservation science, and the citizen activists, particularly in how the latter could be engaged with and lead on the connected ecological reserve design. It would be a process that would build respect for wild nature, a citizen engagement activity that is sorely needed across the whole spectrum of nature conservation in the UK. This uniqueness comes down to modus operandi, to the wildlands network design planning meetings where everyone worked together, that each had their talent and knowledge to contribute (37) and which turns on its head the UK conservation industry approach of its appropriation of process with only token participation from the public. The rewilding approach of TWP was science-based and design-led because of the fundamental realisation of the limitations of isolated reserves being able to capture and preserve the totality of a regional native diversity across its natural range of variation, and with native species in natural patterns of abundance and distribution (36). This was recognition of the implications of extinction dynamics, island biogeography, and metapopulation theory, which would subvert conservation through ecosystem decline in an unconnected landscape. The aim therefore was to identify undisturbed core reserve areas for wild nature within a region, ensure their effectiveness in the immediate location by encircling with areas of compatible land use, and then critically connecting the core areas across the region by identifying wildlife movement linkages that ensured free flow of species, and thus also genes (see Figure IV.1 in (38)). This connectivity would require a meaningful coexistence between wild nature and human land use, its negotiating with land users being a key part of wildlands network design (5,37). The design process was not just some scribbling on a map, because the location of each component of the network design had to be arrived at through matching its restoration potential and biological utility to a target group of species that together best represented the needs of that regional diversity (36). The overall size of the wildlands network had to ensure perpetuation of self-regulating land communities, thus accommodating viable populations of area-demanding species, the strongly interactive species, like large carnivores and herbivores at ecologically effective densities, and in the pursuit of maintenance of ecological and evolutionary processes, such as natural disturbance regimes (wildfire, windstorms and flood) and recovery processes (revegetation), nutrient cycles, hydrological processes, weathering and erosion, seed dispersal, pollination, and the biotic interactions of decomposition, herbivory, and predation (and see (39)). It was a science-based approach to preservation of wild nature that went past a compositional or hotspot approach to reserve identification (our system in the UK) and which made redundant the argument between one large or many small reserves, as well as making irrelevant the distinction between land sparing and land sharing, since both were characteristic of components of the wildlands network design. Wild nature is not fenced Movement, dispersal, migration, and foraging are the changes in spatial location driven by processes that act across space and time that determine the fate of species - the structure and dynamics of populations, communities, and ecosystems, and the evolution and diversity of life (40). Wild nature has no fences to block that movement ecology, and rewilding shouldn’t either. Movement ecology and trophic ecology are not somehow different depending on which continent you are on, and thus it’s ecologically illiterate to claim that rewilding is different in Europe, that it is achieved with the actions of domesticated livestock enclosed by fencing. Moreover, with the presence of wolves now in every country in continental Europe, the incorrect labelling of the origins of rewilding being tied to large carnivore conservation is as irrelevant as it is also ecologically illiterate, so even that hackneyed reason for redefinition of rewilding to European circumstances no longer obtains. Mark Fisher 22 September, 10 October 2019 (1) Is Cairngorms Connect a rewilding project? Frequently Asked Questions. Cairngorms Connect http://cairngormsconnect.org.uk/about/faqs (2) PROJECTS, Endangered Landscapes Programme, Cambridge Conservation Initiative https://www.endangeredlandscapes.org/projects/ (3) Fisher, M. (2003) Self-willed land - the rewilding of open spaces in the UK. 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