Ecological research can augment restoration practice in urban areas degraded by invasive species – examples from Chicago Wilderness
Since I spent most of my weekend working on this - and it relates directly to our class material, I thought I might share this with you:
In one of the foundational gestures of American environmental action David Henry Thoreau walked out of town: “It is hard for me to believe” he informs us, “that I shall find fair landscapes or sufficient wildness and freedom behind the eastern horizon. I am not excited by the prospect of a walk thither; but I believe that the forest which I see in the western horizon stretches uninterruptedly toward the setting sun, and there are no towns nor cities in it of enough consequence to disturb me” (Thoreau 1862). The wildness towards which Thoreau sauntered is the territory that subsequently and overwhelmingly attracted the attention of the nascent environmental movement and the sciences that ultimately supported it (Worster 1994; Nash 2001). Although wilderness has not been an exclusive preoccupation of ecologists and conservationists in the last century, the attraction of the pristine, the unmanaged, the spatially immense, and the wild can be traced through the development of both ecological theory and conservation practice. The fitful ontogeny of salient theorizing on succession (Cowles 1899; Niering 1987), and the early failure to recognize and adequately incorporate disturbance into ecological thinking (Pickett 1980; Sousa 1984; Hobbs et al. 1992) illustrates the difficulties of constructing a comprehensive and ultimately pragmatic ecological science when researchers are intellectually bedazzled by wilderness. A realization by ecologists concerning the theoretical (in)adequacy of their science (McIntosh 1987) for reasons that include, but not are not confined to those sketched above, was paralleled by a close scrutiny by social scientists and humanities scholars of the rigor, and the potential obfuscations arising from the very notion of wilderness. For instance, Denevan (1992) argued that the ‘pristine myth’ underestimated both the size of the human population and the extent of human disturbance in the Americas prior to 1492. Cronon (1996) and Callicott and Nelson (1998) collect some of this literature which purportedly finds wilderness and the thicket of thinking and practice that emerge from this notion to be intellectually insubstantial.
The sense that a preoccupation with wilderness has not provided a fully adequate substrate for ecology, for reasons of its factual sufficiency (areas regarded as wilderness may in a number of instances have been used by indigenous peoples) and its philosophical diffuseness (wilderness as an idea, and not just a place), does not, of course, minimize the importance of historical and ongoing work directed at locations at the lower end of a gradient of human use (whether designated as wilderness or not). However, I suggest that the mesmeric draw of the untrammeled has bequeathed to us an unbalanced spatial preoccupation in our ecological thinking – ecologically healthy lands are always elsewhere, rarely where the ecologist or conservation practitioner lives. The ecology of human dominated landscapes has been therefore been neglected at the expense of wildlands and this occlusion has delayed the emergence of an effective program of research to serve and inspect conservation practice in areas of high human density and land use.
There is now a recognition that this imbalance in ecology needs to be redressed, and a variety of well funded projects are underway designed to provide a firm theoretical and empirical basis for urban ecology (Pickett et al. 2001; Grimm et al. 2004). The importance of this reconfiguration in ecology is not just that it complements and challenges the discipline as a whole, but that it also provides an opportunity to calibrate theory developed in areas of lower human impact for its application in areas of high human density where the designation of land use is more highly variegated. It is worth mentioning that agro-ecology also required a reconfiguration of ecological sciences, deflecting the discipline from its contemplation of wild nature and towards some very specific outcomes, notably the resource efficient enhancement of the productivity of a monoculture (Jackson et al. 1989; Paul et al. 1989). In addition to the utility for the discipline itself of extending its ontological breadth into the novel anthro-habitats of the metropolis, applying the purview of ecology to the city may stimulate fresh perspectives on practices within the city. These include potential contributions to urban design, architecture, resource sustainability but also, and this is the primary focus of the remainder of this study, to urban biodiversity conservation (Jackson 2003). In return, a rigorously conceived urban ecology where the ecosystem and the social system are appropriated annealed may radicalize (and unify) ecology. From this new perspective wilderness may be seen as a special case, rather than the foundational case, against which all is compared and deemed, usually, to have failed. This view of wilderness would remain intellectually generous to the wild, but would be profoundly reorient our views.
Problems and opportunities associated with urban conservation have assumed a growing importance in the consciousness of environmental advocates (Harrison et al. 2002; Rudd et al. 2002; Crane et al. 2005). In some instances conservation in highly fragmented urban areas contributes in quantitatively significant ways to conservation goals. In the case of the larger Chicago metropolitan region, for example, a vigorous ecological restoration movement contributes in quantitatively meaningful ways to conservation in Illinois (Stevens 1996; Wang et al. 2001). This is because many of the higher quality residual fragments of presettlement habitat are preserved in the hinterland of the city, whereas, by virtue of the fertility of its prairies soils the extensive rural landscapes of the state are dominated by intensive agriculture with consequent depletion of biodiversity (Cronon 1992; Warner 1994). Even where the cumulative impact of urban conservation is modest in both its success and its extent compared to conservation in more traditional preserves, the efforts of urban conservations may contribute in an underappreciated way to conservation outcomes. This emerges from the intersection of the social system (individuals, institutions, beliefs, behavior etc.) that motivates and sustains the conservation effort in the city with the ecological system that these conservations seek to protect. Jordan (2003) refers to the multiple values that emerge from ecological restoration as a conservation strategy for both the people and the systems to which they attend. At the very least, urban conservation, even when limited in scale, gives urban dwellers an opportunity to see and to value native communities, and these citizens may subsequently be more inclined to promote support for conservation policy directed at locations distant from the seat of power.
Biodiversity in the city – Chicago remains paradigmatic here – is spatialized in ways that we have only in the last generation developed the tools to deal with (practical tools like Geographical Information Systems and theoretical ones like island biogeographic theory, patch dynamics, and metapopulation dynamics). Habitats of conservation value in cities are part of an interstitial ecology, and biodiversity is often where you least expect it: in pavement cracks and crevices (Chronopoulos et al. 2000), along transportation rights of way (Bowles et al. 2003), in disused or abandoned patches (Goode 1989): all invariably representing fragments of formerly contiguous pre-urbanized communities that are now arrayed along a gradient of historical land use and human impact (Kent et al. 1999). Because of the landscape context, urban habitat fragments are confronted with a suite of problems that make their long-term sustainability improbable without management. An analysis of threats to terrestrial habitats in Chicago identify hydrological changes, fragmentation, altered fire regimes, loss of structural diversity, nutrient loading, increased salinity, erosion and increase sedimentation, invasive species, overgrazing by deer, as well a variety of other human impacts (Council 1999). In the face of such problems, conservation strategies that merely set aside land of conservation interest are not destined to success and require, therefore, intervention in the form of management. Although the causes of habitat decline in their urban interstitial locations have been well characterized, and the stresses enumerated above may serve as a point of analytic departure elsewhere, it is clear that these factors are interrelated in complex ways. For instance, habitats that are highly fragmented, nutrient loaded, unburned (where burning is the historical maintenance pulse (sensu Odum (1969)) become vulnerable to exotic species invasion (Rejmanek 1996; Davis et al. 2000). Invaded sites loose structure diversity, become further invaded, and in some case are more susceptible to soil erosion (Crooks 2002). Although the tasks that face the restorationist are many (Packard et al. 1997) and the removal of invaders consumes a significant share of the work in most parts of the world where restoration is undertaken (D'Antonio et al. 2002), it is not always clear that this removal is effective or without unforeseen complications (Gordon 1998; Zavaleta et al. 2001). In particular, many invasive species may impose changes to ecosystem process and the invaded systems remain in resilient altered states even after the structural removal of the invaders (Suding et al. 2004). Ecological restoration has not, arguably, developed a reflexive practice that rapidly accommodates such challenges – where there are no clear goals set for restoration there is little incentive to evaluate outcomes and modify practice in the face of new challenges (Choi 2004). It is not at all apparent, on the other hand, that there has been a willingness by ecologists to draw upon the experiences of managers, a attentiveness to which would undoubtedly enhance development of theory.
With the confluence of the following features (ones discussed in a very preliminary way above): the inauguration of the discipline of urban ecology with its willingness to attend to both new theory and emerging practice, the recognition that metropolitan areas contain habitat that may have a quantitatively or qualitatively important role to play in global biodiversity conservation, the realization that this task requires active management, rather than passive preservation, the establishment of professional cadre of restorationists working on conservation lands, and the emergence of a strong volunteer restoration movement to serve the needs of management goals, one might feel cautiously optimistic about conservation in these circumstances. However, despite these promising convergences there are fundamental obstacles to success – gaps in knowledge about species and processes in urban habitats, inadequate monitoring of the results of management, limited public understanding of the aims of urban conservation, and the poverty of predictive models of invasion. This list, not intended to be exhaustive, is sufficiently ample to underscore an obvious phenomenon, there exists no productive relationship between the emerging science undergirding ecosystem management and the management practice itself. That is not to say that no affability exists between researchers and land managers there is however a pattern of failed engagement between these two constituencies (Huenneke 1995; Underwood 1995). Mary Midgely (2001) illuminates the problem. “The conclusion” she states, “is that problems are not private property. They belong to anyone who can help to solve them. The advance of specialization makes it harder to grasp this these today, but it certainly does not make it less necessary.” Midgely, a philosopher, is in this instance referring to ‘the problem of consciousness’ which she claims “is beginning to worry scholars in a number of disciplines, including those in which, until lately, that word was not supposed to be heard at all…. [S]pecialists will have to try to cooperate over them, hard though that may be.” One does not need to look hard for expression of exasperation regarding the difficulty of tackling inherently interdisciplinary problems even in more immediately applied circumstances. Lefebvre (2003), an urban sociologist, brings the matter closer to home: “This complexity makes interdisciplinary cooperation essential… [However] [t]he illusion of such studies, and the myths surrounding them, have been abundantly criticized. Participants at colloquia…[r]arely … agree on the words and terms they use, and even less rarely on the underlying concepts…. Confrontation and disagreement pass for success.” The challenge that awaits urban ecology and restoration ecology as sciences where these have practical outcomes in mind is to develop an optimal and useful relationship with land managers, conservation volunteers, landowners and policy advocates. The fact that such relationships are difficult ones should embolden us to try harder.
In the remainder of this paper I will develop a case study, that of the impact of Rhamnus cathartica on ecosystem properties in relictual woodlands in metropolitan Chicago. The example demonstrates the degree to which restoration practice can provide stimulating questions for ecological research and how the results of this work may complicate restoration practice. When results relevant to practice emerge from restoration ecology, it is inherently difficult to implement them into practice, for reasons identified above, and further discussed below. I will conclude with suggestions for developing a reciprocal model for moving theory and practice forward, in a manner that may be useful for both sides of the debate. The region in which this research is being conducted is referred to as Chicago Wilderness. The region embraces 200,000 acres of openlands throughout in Southeastern Wisconsin, Northeastern Illinois, and Northwestern Indiana, an area, perhaps surprisingly, with a rich natural history (Greenberg 2002). Chicago Wilderness also refers to the coalition of over 180 organizations (land agencies, museums, universities, arboreta, planning agencies, municipalities, etc.) that work towards preservation in this region (www.chicagowilderness.org)
The sense that a preoccupation with wilderness has not provided a fully adequate substrate for ecology, for reasons of its factual sufficiency (areas regarded as wilderness may in a number of instances have been used by indigenous peoples) and its philosophical diffuseness (wilderness as an idea, and not just a place), does not, of course, minimize the importance of historical and ongoing work directed at locations at the lower end of a gradient of human use (whether designated as wilderness or not). However, I suggest that the mesmeric draw of the untrammeled has bequeathed to us an unbalanced spatial preoccupation in our ecological thinking – ecologically healthy lands are always elsewhere, rarely where the ecologist or conservation practitioner lives. The ecology of human dominated landscapes has been therefore been neglected at the expense of wildlands and this occlusion has delayed the emergence of an effective program of research to serve and inspect conservation practice in areas of high human density and land use.
There is now a recognition that this imbalance in ecology needs to be redressed, and a variety of well funded projects are underway designed to provide a firm theoretical and empirical basis for urban ecology (Pickett et al. 2001; Grimm et al. 2004). The importance of this reconfiguration in ecology is not just that it complements and challenges the discipline as a whole, but that it also provides an opportunity to calibrate theory developed in areas of lower human impact for its application in areas of high human density where the designation of land use is more highly variegated. It is worth mentioning that agro-ecology also required a reconfiguration of ecological sciences, deflecting the discipline from its contemplation of wild nature and towards some very specific outcomes, notably the resource efficient enhancement of the productivity of a monoculture (Jackson et al. 1989; Paul et al. 1989). In addition to the utility for the discipline itself of extending its ontological breadth into the novel anthro-habitats of the metropolis, applying the purview of ecology to the city may stimulate fresh perspectives on practices within the city. These include potential contributions to urban design, architecture, resource sustainability but also, and this is the primary focus of the remainder of this study, to urban biodiversity conservation (Jackson 2003). In return, a rigorously conceived urban ecology where the ecosystem and the social system are appropriated annealed may radicalize (and unify) ecology. From this new perspective wilderness may be seen as a special case, rather than the foundational case, against which all is compared and deemed, usually, to have failed. This view of wilderness would remain intellectually generous to the wild, but would be profoundly reorient our views.
Problems and opportunities associated with urban conservation have assumed a growing importance in the consciousness of environmental advocates (Harrison et al. 2002; Rudd et al. 2002; Crane et al. 2005). In some instances conservation in highly fragmented urban areas contributes in quantitatively significant ways to conservation goals. In the case of the larger Chicago metropolitan region, for example, a vigorous ecological restoration movement contributes in quantitatively meaningful ways to conservation in Illinois (Stevens 1996; Wang et al. 2001). This is because many of the higher quality residual fragments of presettlement habitat are preserved in the hinterland of the city, whereas, by virtue of the fertility of its prairies soils the extensive rural landscapes of the state are dominated by intensive agriculture with consequent depletion of biodiversity (Cronon 1992; Warner 1994). Even where the cumulative impact of urban conservation is modest in both its success and its extent compared to conservation in more traditional preserves, the efforts of urban conservations may contribute in an underappreciated way to conservation outcomes. This emerges from the intersection of the social system (individuals, institutions, beliefs, behavior etc.) that motivates and sustains the conservation effort in the city with the ecological system that these conservations seek to protect. Jordan (2003) refers to the multiple values that emerge from ecological restoration as a conservation strategy for both the people and the systems to which they attend. At the very least, urban conservation, even when limited in scale, gives urban dwellers an opportunity to see and to value native communities, and these citizens may subsequently be more inclined to promote support for conservation policy directed at locations distant from the seat of power.
Biodiversity in the city – Chicago remains paradigmatic here – is spatialized in ways that we have only in the last generation developed the tools to deal with (practical tools like Geographical Information Systems and theoretical ones like island biogeographic theory, patch dynamics, and metapopulation dynamics). Habitats of conservation value in cities are part of an interstitial ecology, and biodiversity is often where you least expect it: in pavement cracks and crevices (Chronopoulos et al. 2000), along transportation rights of way (Bowles et al. 2003), in disused or abandoned patches (Goode 1989): all invariably representing fragments of formerly contiguous pre-urbanized communities that are now arrayed along a gradient of historical land use and human impact (Kent et al. 1999). Because of the landscape context, urban habitat fragments are confronted with a suite of problems that make their long-term sustainability improbable without management. An analysis of threats to terrestrial habitats in Chicago identify hydrological changes, fragmentation, altered fire regimes, loss of structural diversity, nutrient loading, increased salinity, erosion and increase sedimentation, invasive species, overgrazing by deer, as well a variety of other human impacts (Council 1999). In the face of such problems, conservation strategies that merely set aside land of conservation interest are not destined to success and require, therefore, intervention in the form of management. Although the causes of habitat decline in their urban interstitial locations have been well characterized, and the stresses enumerated above may serve as a point of analytic departure elsewhere, it is clear that these factors are interrelated in complex ways. For instance, habitats that are highly fragmented, nutrient loaded, unburned (where burning is the historical maintenance pulse (sensu Odum (1969)) become vulnerable to exotic species invasion (Rejmanek 1996; Davis et al. 2000). Invaded sites loose structure diversity, become further invaded, and in some case are more susceptible to soil erosion (Crooks 2002). Although the tasks that face the restorationist are many (Packard et al. 1997) and the removal of invaders consumes a significant share of the work in most parts of the world where restoration is undertaken (D'Antonio et al. 2002), it is not always clear that this removal is effective or without unforeseen complications (Gordon 1998; Zavaleta et al. 2001). In particular, many invasive species may impose changes to ecosystem process and the invaded systems remain in resilient altered states even after the structural removal of the invaders (Suding et al. 2004). Ecological restoration has not, arguably, developed a reflexive practice that rapidly accommodates such challenges – where there are no clear goals set for restoration there is little incentive to evaluate outcomes and modify practice in the face of new challenges (Choi 2004). It is not at all apparent, on the other hand, that there has been a willingness by ecologists to draw upon the experiences of managers, a attentiveness to which would undoubtedly enhance development of theory.
With the confluence of the following features (ones discussed in a very preliminary way above): the inauguration of the discipline of urban ecology with its willingness to attend to both new theory and emerging practice, the recognition that metropolitan areas contain habitat that may have a quantitatively or qualitatively important role to play in global biodiversity conservation, the realization that this task requires active management, rather than passive preservation, the establishment of professional cadre of restorationists working on conservation lands, and the emergence of a strong volunteer restoration movement to serve the needs of management goals, one might feel cautiously optimistic about conservation in these circumstances. However, despite these promising convergences there are fundamental obstacles to success – gaps in knowledge about species and processes in urban habitats, inadequate monitoring of the results of management, limited public understanding of the aims of urban conservation, and the poverty of predictive models of invasion. This list, not intended to be exhaustive, is sufficiently ample to underscore an obvious phenomenon, there exists no productive relationship between the emerging science undergirding ecosystem management and the management practice itself. That is not to say that no affability exists between researchers and land managers there is however a pattern of failed engagement between these two constituencies (Huenneke 1995; Underwood 1995). Mary Midgely (2001) illuminates the problem. “The conclusion” she states, “is that problems are not private property. They belong to anyone who can help to solve them. The advance of specialization makes it harder to grasp this these today, but it certainly does not make it less necessary.” Midgely, a philosopher, is in this instance referring to ‘the problem of consciousness’ which she claims “is beginning to worry scholars in a number of disciplines, including those in which, until lately, that word was not supposed to be heard at all…. [S]pecialists will have to try to cooperate over them, hard though that may be.” One does not need to look hard for expression of exasperation regarding the difficulty of tackling inherently interdisciplinary problems even in more immediately applied circumstances. Lefebvre (2003), an urban sociologist, brings the matter closer to home: “This complexity makes interdisciplinary cooperation essential… [However] [t]he illusion of such studies, and the myths surrounding them, have been abundantly criticized. Participants at colloquia…[r]arely … agree on the words and terms they use, and even less rarely on the underlying concepts…. Confrontation and disagreement pass for success.” The challenge that awaits urban ecology and restoration ecology as sciences where these have practical outcomes in mind is to develop an optimal and useful relationship with land managers, conservation volunteers, landowners and policy advocates. The fact that such relationships are difficult ones should embolden us to try harder.
In the remainder of this paper I will develop a case study, that of the impact of Rhamnus cathartica on ecosystem properties in relictual woodlands in metropolitan Chicago. The example demonstrates the degree to which restoration practice can provide stimulating questions for ecological research and how the results of this work may complicate restoration practice. When results relevant to practice emerge from restoration ecology, it is inherently difficult to implement them into practice, for reasons identified above, and further discussed below. I will conclude with suggestions for developing a reciprocal model for moving theory and practice forward, in a manner that may be useful for both sides of the debate. The region in which this research is being conducted is referred to as Chicago Wilderness. The region embraces 200,000 acres of openlands throughout in Southeastern Wisconsin, Northeastern Illinois, and Northwestern Indiana, an area, perhaps surprisingly, with a rich natural history (Greenberg 2002). Chicago Wilderness also refers to the coalition of over 180 organizations (land agencies, museums, universities, arboreta, planning agencies, municipalities, etc.) that work towards preservation in this region (www.chicagowilderness.org)
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