Philosophical approaches to habitat management
Philosophical approaches to habitat management
Abstract and Keywords
This chapter discusses the various philosophical approaches to habitat management. The fundamental differences between approaches concerns how management aims to create and maintain cultural habitats that existed under more natural conditions, and the level of human intervention and control. Habitat management may involve very specific actions aimed primarily at benefiting just one or a small suite of species, or it may involve introducing key natural processes with little further intervention and expectation of the outcome. Approaches to habitat management also depend on the extent to which conservation is integrated with other interests, such as recreation, wider resource use, and provision of other ecological services.
There are a range of philosophical approaches to habitat management. Fundamental differences involve whether management aims to create and maintain cultural habitats or those considered closer to habitats that existed under more natural conditions, and the level of human intervention and control. At one extreme, habitat management may involve very specific actions aimed primarily at benefiting just one or a small suite of species. At the other, it may involve introducing key natural processes with little further intervention and expectation of the outcome.
The approach to habitat management also depends on the extent to which conservation is integrated with other interests, such as recreation, wider resource use and provision of other ecological services. A further consideration at a higher level is the extent to which resources are focused on achieving conservation objectives in protected areas and nature reserves, compared with on farmed land in the wider landscape (Figure 2.1).
2.1 Preserving cultural habitats or managing change
In many areas of the world, particularly much of Europe, the only existing areas of near-natural habitat are cultural habitats that have been subject to long periods of human resource use. The usual starting point when considering management of these cultural habitats is to continue, or reinstate, similar management to that which created and maintained them. This is based on the assumption that if the desired assemblage of species already co-existed under a particular management regime, then the best way to perpetuate it is to continue, or reinstate, a similar regime. Introduction of different management might provide even better conditions for some of the species already present. In fact, they might have persisted more despite existing management, rather than because of it. Introduction of different management might also provide suitable conditions for species not currently (p.14)
Despite these strong arguments for continuing or reinstating traditional management in cultural habitats, there are number of reasons why this may not always be the best method of conserving species in them. In some cases, what is currently considered to have been traditional management may in fact have varied quite significantly over time. For example, at Wicken Fen, one of the UK's oldest (p.15)
The most important reason, though, why reliance on traditional-type management may not be the best option, is because of more recent human-induced changes in the wider environment. The most important of these are:
• changes in climate (Section 4.7);
• increases in nutrient levels influencing plant growth (Section 4.1.1);
• acidification of soils and water bodies (Section 6.5.2);
• changes due to population processes and numbers of generalist predators in the wider landscape (Section 4.2).
(p.16) A further reason why reliance on traditional management may not always be the best option is due to its often high costs. Most traditional management of cultural habitats of high conservation value is now uneconomic, unless supported by grants (it is important to note that most conventional agriculture is also heavily subsidized).
For the reasons discussed, it may be more useful to consider management of cultural habitats more as a process of managing inevitable change. This involves maximizing the positive effects of these changes and minimizing their negative effects, rather than merely seeking to conserve or preserve assemblages of species that happened to be present when the decision to conserve the area was made.
If it is intended to introduce new forms of management, it is still prudent to trial this new management over just a portion of the site. If the new management proves unsuitable for existing species, then they should at least persist in nearby habitat not subject to this change. It is also important to monitor changes taking place under both the new and existing management regimes to help understand the effects of the new management (Section 3.2).
2.2 Recreating former cultural habitats or creating new ones
There is less of a case for relying on traditional management techniques when designing the creation and management of new areas of habitat on land of low or negligible conservation value. In these situations there is no need to use traditional management to perpetuate assemblages of species of conservation value already present. Instead, there is greater freedom to create conditions not provided in cultural habitats, and thereby cater for different assemblages of species. There is also greater potential to manage such areas less intensively, with a greater reliance on more natural processes of vegetation removal and physical disturbance. This has the advantages of providing a greater sense of wilderness and will in many cases be cheaper than maintaining them using traditional management. A frequently cited example of this approach is management of the Oostvaardersplassen in the Netherlands (see Figure 4.6). In some cases, though, there may be other cultural or historic reasons for creating cultural habitats, including increasing the size and potential viability of existing fragments.
2.3 The level of intervention: focusing on individual species or encouraging natural processes?
A fundamental decision when undertaking habitat management is the level of intervention. In some situations there is the potential to manage habitats (p.17) specifically to benefit just one or a small suite of species. In practice, this invariably involves maintaining the habitat in a suitable condition for its characteristic assemblages of species, but refining the details of this management to specifically benefit one or a group of them. This approach has been successful at reversing declines of species of high conservation value, but its success is obviously dependent on a correct diagnosis of the reasons for decline (Green 1995). The more single-species-led approach to habitat management has been most often used to benefit birds and some other popular groups, such as butterflies.
Focusing on the requirements of individual species, rather than the habitat or ecosystem as a whole, is viewed by some people as being too interventionist and controlling, and far removed from their philosophical view of what wild nature is really about. Focusing on single species also means it is necessary to decide, through valued judgement, which species to benefit, and in some cases which species to disadvantage, through management. The latter can be contentious, especially when involving control of predators.
Even if the main aim of management is to benefit particular species or groups, a decision still needs to be made regarding the level of intervention. This is well illustrated by the range of management options available for increasing food supply for wintering seed-eating wildfowl. The quantity of seed available to them can be increased by artificially manipulating water levels to maximize the growth of abundant seed-producing ruderal vegetation, using moist-soil management (Section 8.4.1). Although this is clearly a management intervention, it still largely mimics the natural process of the seasonal drawing down of water levels. A further intervention would be to sow favoured wildfowl foods within these wetland areas to increase the quantity of suitable seed. More interventionist still would be to grow and leave unharvested favoured wildfowl foods on arable land using conventional farming methods, so-called sacrificial crops (Section 10.5). The most extreme end of the naturalness–unnaturalness continuum would be to simply feed wildfowl with grain (Figure 2.3). Individuals and organizations differ in the level of intervention they consider acceptable.
There are a number of important practical advantages in focusing habitat management to benefit individual species. It results in the setting of clear, unambiguous targets for management, and clear actions to achieve these targets, providing that the key species’ habitat requirements are well understood. It is therefore a strong tool for focusing minds and resources. This approach can be used to define targets for species (and habitats) at national and other levels that can be cascaded down to those at individual sites. This type of planning approach has the advantages of providing a standard ‘language’ with which to define priorities and allocate resources. In the event of these targets not being achieved, organizations and (p.18)
The other extreme to focusing on the requirements of favoured individual species is to focus on restoring or maintaining key natural processes. These may include introducing naturalistic, large-scale grazing and flooding regimes, and then allowing them to operate with minimal further intervention. Encouragement of so-called keystone species also falls into this category. These are species which have an important influence on ecosystem function and biological diversity disproportionate to their numerical abundance. Examples include beavers through their damming activities, prairie dogs, Cyonomys spp., and European rabbits Oryctolagus cuniculus because of their effects on the vegetation and importance as prey for a wide range of species, and large carnivores that influence the numbers and grazing patterns of large herbivores (Figure 2.4). The main advantages of such an approach are the high level of perceived naturalness, lower ongoing maintenance costs and the potential to support species rare or absent from more intensively managed habitats.
Discussions over the level of control and intervention to apply when managing habitats for conservation often focus on the level of control over grazing regimes (Section 4.4.1). This can vary from, at one extreme, grazing for discrete periods of the year at prescribed stocking levels, to naturalistic grazing by free-ranging mixtures of large herbivores. A logical continuation of this decreasing level of intervention is the process of rewilding. This aims to restore large, strictly protected core wilderness areas, connected by corridors and supporting free-ranging large herbivores and large carnivores and other keystone species (Noss (p.20) and Soulé 1998). Some proponents of rewilding even suggest the introduction into North America of African and Asian megafuana, such as lions Panthera leo, cheetahs Acinonyx jubatus, Asian elephants Elaphus maximus and African elephants Loxodonta africana, to perform similar ecological roles to their now extinct North American equivalents (Donlan et al. 2005).
Introducing natural processes and letting them operate with minimal intervention is in many cases unlikely to create systems very similar to those that occurred naturally, because land use has changed. An example would be the re-naturalization of river floodplains (Figure 2.5). Simply removing artificial river walls to recreate a naturally functioning floodplain is unlikely to recreate similar conditions to those that occurred under natural conditions. The land in the floodplain will usually have been levelled to allow agricultural activities, thus removing its natural variation in topography and hydrology, and consequently reducing the variation in habitat conditions that will subsequently develop. Artificial drainage within the rest of the catchment will increase the rate of runoff following storm events, and create a higher and more short-lived flood peak. If the re-naturalized area forms only part of the floodplain, then it will receive a larger quantity of floodwater than if the water was able to spread over the entirety of the original floodplain. The fertility of the floodplain will also be higher than under natural conditions, due to anthropogenic nutrient inputs within the catchment. There will also be less than a full compliment of large herbivores to graze the vegetation. The way to make the resulting habitats more similar to those that existed under natural conditions would be to use further intervention to recreate variation in topography through land-forming, and introduce management by livestock to mimic the effects of now absent large herbivores. Often, leaving areas to nature will produce conditions quite different to those that occurred in an original, natural state.
The concept of naturalness is frequently used when discussing habitat re-creation/restoration and management. In practice, there is no single natural state of a site. There are, though, a number of different forms of naturalness, as described by Peterkin (1981). These are:
• original-naturalness: the state that existed prior to human influence;
• present-naturalness: the state that would exist now if there had been no human influence;
• past-naturalness: the quality associated with sites whose components have been inherited directly from the original state that existed prior to human influence;
• potential-naturalness: the state that would in theory exist if human influence was removed now and the site instantaneously developed into the successional state that it would ultimately achieve following this removal of human influence;
• future-naturalness: the state that would eventually develop if human influence was removed now and remained permanently removed.
2.4 Integrating habitat management with other interests and values
Like it or not, nature conservation per se is a minority interest. Even for people who regularly visit non-urban areas, the most highly valued features are usually the landscape, presence of livestock or sense of wilderness, rather than their specific biodiversity value. For nature conservation to maximize its potential, it therefore needs to be integrated with other interests including health and well-being (Figure 2.6) and its economic case made in terms of the entire range of benefits provided by more sustainable land management (Figure 2.7).
At a site-based decision-making level, consideration needs to be given to the extent that habitat management for nature conservation is integrated with, or even compromised by:
• education and research;
• landscape and aesthetic considerations;
• cultural history;
• resource use;
• provision of wider environmental benefits, like ecosystem services such as flood protection.
(p.25) In the case of cultural habitats of high conservation, cultural or landscape value, the emphasis is on maintaining these invariably open, early successional habitats and their associated species through continuation, reinstatement or modification of former land use. Introduction of other management that relies on the reinstatement of near-natural ecological processes will inevitably lead to an impoverishment of their existing suites of species and loss of cultural and existing landscape value. Where more pristine areas of habitat remain, there will be a greater emphasis on maintaining these large, near-natural areas through minimal human intervention. It would be absurd to introduce intensive, small-scale management to large areas of near-natural wilderness. The interesting area of debate, though, concerns how to manage medium-sized areas of less highly valued cultural habitat, and in particular how to design and manage newly created habitat within otherwise intensively managed landscapes: whether to recreate cultural habitats or landscapes or something different.
Introducing and maintaining key natural processes might have many benefits, particularly in terms of its perceived level of naturalness and the potentially low ongoing management costs. However, it is also clear that no sites can ever be considered fully natural because of their past modification, the influence of wider human activities and because they are unlikely to be large enough to operate in a truly natural way. We have also seen that there is no all-embracing, natural state of a habitat. The best we can hope to achieve when seeking to create ‘natural’ habitats is to choose some desirable past-, present- or future-natural state to aim at.
Any desire to allow natural processes to take precedence has therefore to be tempered with pragmatism. The approach will usually be to let natural processes and functions operate as far as practical, while recognizing that on occasions more interventionist management may be necessary to conserve species considered to be of high value. It is also important to distinguish between encouraging natural processes to create conditions closer to what we consider to be original-naturalness, and viewing the introduction of key natural processes more as an end in itself.
Management of an existing site may often involve extending its area to increase the long-term viability of populations of desired species, and decrease unit management costs. Where this is the case a combination of traditional and more naturalistic management may be appropriate. The existing fragment of habitat may have to continue to be managed (p.26) through traditional management in the short term to maximize the chance of maintaining its existing species compliment. Meanwhile, the newly created habitat surrounding it could be managed less intensively at lower unit cost. The intention would be that the highly valued species maintained by intensive management will in time colonize the surrounding, less intensively managed land. Once this has happened, the whole area could then be managed less intensively with little risk of extinction of the then more widespread, highly valued species.