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1.
Fire has been considered one of the most important factors in the expansion of savannas in the Gran Sabana region. In Urué, an important fire event that occurred before 1.6 kyr BP led to the replacement of ‘primary’ forests by savannas and morichales (monospecific communities of the palm Mauritia). In the present work, the secondary succession after fire is reconstructed by palynological analysis of a previously dated clay core, and the results are compared with those from studies based on present‐day ecosystems. Charcoal analysis is used to infer fire incidence and surface samples are used as modern analogues. The secondary succession is subdivided into seven seral stages: open secondary forests, helechal or dense fern community, transitional savanna, wet savanna with morichales, treeless savanna, wet savanna with morichales, and treeless savanna. Fires were common at the beginning, but climate constituted the main successional control from the transitional savanna stage onwards. The process is characterised by a continuous impoverishment of taxa, but there was a steady increase in Mauritia, due to its ability to colonise new habitats created by disturbances. The conclusions of this palynological reconstruction show good correspondence with present‐day studies on fire ecology. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

2.
This article argues that insufficient attention has been paid in the recent literature to the social and environmental factors which regulate hunting in Ghanaian savannas, and to how this may influence the sustainability of their livelihoods. Despite the vital significance of this issue, the emphasis in the literature and media has been on the destructive impacts of hunting and the bushmeat trade on wildlife. Taking a case study from the coastal savanna of Ghana, a region commonly regarded as a degraded relict of former deciduous forest with a richer wildlife past, it investigates the hypothesis that structure/actor dualities, manifested by socio-cultural change, local environmental knowledge and livelihood activity options, are the primary regulators of hunting intensity and possible sustainability. Such an evaluation is effective if done from a structuration perspective. The integrated methodology incorporates social surveys, GIS based time series image analysis, ecological field methods and statistical analysis. The results provide evidence that the direct and indirect regulatory functions of the socioenvironmental context provide a core feature of the sustainability of hunting. It is concluded that local strategies of resource management may provide an effective complement to conservation policy.  相似文献   

3.
Bjørn Sletto 《Geoforum》2011,42(2):197-210
Conflicts surrounding protected area management often emerge from contested processes of boundary-making. Such productions of bounded conservation spaces are contingent in part on processes of identity formation, where some social groups are legitimized as belonging to conservation units, while others are constructed as out-of-place. This article draws on the literature in postmodern geopolitics and the political ecology of fire to interrogate processes of boundary-making and identity formation in the savanna landscape of Canaima National Park, Venezuela. The institutional culture of the environmental management agency EDELCA is in part premised on narratives of history and indigeneity coupled with a desire for an imagined, forested landscape. Because of the social constructions shaping this institutional culture, the agency maintains an approach to fire management that emphasizes fire suppression. However, an ecological field study suggests that fire suppression is leading to increased fuel loads, especially in ecologically significant boundaries between grasslands and forest. Although these boundary zones are the focus of indigenous practices of prescribed burning, they fall in-between the state management categories of forest and ecotone. As a result, these interstitial spaces become theaters for performances of domination and resistance, leading to contradictory and inconsistent approaches to fire management that place gallery forests at risk.  相似文献   

4.
Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO2 concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 14C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 14C yr B.P., coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2-3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.  相似文献   

5.
Grazing and fire are major factors influencing the savanna ecosystems of Southern Africa. In both grazing and conservation areas overgrazing is an important reason for degradation of vegetation and soil. Insufficient fire management can cause a change in the species composition and may influence the soil negatively. For adequate planning purposes the knowledge of available biomass is indispensable. High-resolution satellite systems can provide such knowledge on a large scale. Three study areas in Southern Africa contributed to a first survey. Gutu District is situated in Zimbabwe. In its Communal Lands a high population density leads to severe degradation of vegetation and soil. The South African test sites are located in Kruger National Park and Madikwe Game Reserve. Therefore a wide ecological range from highly degraded to slightly disturbed savanna ecosystems is included. Satellite images of both Landsat-5 (TM) and Landsat-7 (ETM+) were applied. After cross-calibration of the two different satellite systems, indices applied to radiance and reflectance showed significant correlations with ground truth data of grass and other foliage biomass. Including new data from Hluhluwe National Park (South Africa) into the regression models improved the results, indicating that a regional model for savanna ecosystems in Southern Africa could be found. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

6.
This paper presents a theoretical framework for analyzing human–environment issues that examines shifting, dialectical relationships between social and power relations, cultural beliefs and practices, and ecological processes to allow an interdisciplinary, complex assessment of social and environmental change in Nepal. The purpose of this analysis is to capture the complexity and non-static nature of environmental and social change in the context of uneven development. Drawing from political ecology and feminist geography, this framework brings together scholarship on aspects of human–environment issues that are often pursued in isolation, yet all three processes, social–political relations, cultural practices and ecological conditions, have been acknowledged as important in shaping the trajectory of social and ecological change. I argue that a consideration of the articulations between them is necessary to understand first, how specific land management regimes arise and are dominant over time in specific places. And second, I examine the extent to which these regimes distribute resources equitably within communities, promote economic development and sustain ecological resilience. In this analysis, ecological processes are conceptualised as co-productive of social and cultural processes to explore their role in land management regimes without resorting to environmental determinist or similarly reductive paradigms. I present this framework through the example of natural resource management, specifically community forestry in Nepal, as it offers a rich case study of the relationships between the political economy of land use and the ecological effects of natural resource extraction.  相似文献   

7.
Palaeoecology, as an ecological discipline, is able to provide relevant inputs for conservation science and ecosystem management, especially for issues involving long-term processes, such as ecological succession, migration, adaptation, microevolution, and extinction. This use of palaeoecology has been noted for several decades, and it has become widely accepted, especially in the frame of ongoing and near-future global warming and its potential biotic consequences. Selected palaeoecological insights of interest for conservation include the following: 1) species respond in an individualistic manner to environmental changes that lead to changes in community composition, suggesting that future ecosystems would have no modern analogues; 2) in the short-term, acclimation is more likely a response of species that are expected to persist in the face of global warming, but the possibility of evolutionary change linked to the existence of pre-adapted genomes cannot be dismissed; 3) species unable to acclimate or adapt to new conditions should migrate or become extinct, which has been observed in past records; 4) current extinction estimates for the near-future should be revised in light of palaeoecological information, which shows that spatial reorganisations and persistence in suitable microrefugia have been more common than extinction during the Quaternary; 5) biotic responses to environmental changes do not necessarily follow the rules of equilibrium dynamics but depend on complex and non-linear processes that lead to unexpected “surprises”, which are favoured by the occurrence of thresholds and amplifying positive feedbacks; 6) threshold responses can cause the movement of ecosystems among several potentially stable states depending on their resilience, or the persistence of transient states; 7) species and their communities have responded to environmental changes in a heterogeneous fashion according to the local and regional features, which is crucial for present and future management policies; 8) the global warming that occurred at the end of the Younger Drays cold reversal (ca 13.0 to 11.5 cal kyr BP) took place at similar rates and magnitudes compared to the global warming projected for the 21st century, thus becoming a powerful past analogue for prediction modelling; 9) environmental changes have acted upon ecosystems in an indirect way by modifying human behaviour and activities that, in turn, have had the potential of changing the environment and enhancing the disturbance effects by synergistic processes involving positive feedbacks; 10) the collapse of past civilisations under climate stress has been chiefly the result of inadequate management procedures and weaknesses in social organisation, which would be a warning for the present uncontrolled growth of human population, the consequent overexploitation of natural resources, and the continuous increase of greenhouse gas emissions; 11) the impact of fire as a decisive ecological agent has increased since the rise of humans, especially during the last millennia, but anthropic fires were not dominant over natural fires until the 19th century; 12) fire has been an essential element in the development and ecological dynamics of many ecosystems, and it has significantly affected the worldwide biome distribution; 13) climate–fire–human synergies that amplify the effects of climate, or fire alone, have been important in the shaping of modern landscapes. These general paleoecological observations and others that have emerged from case studies of particular problems can improve the preservation of biodiversity and ecosystem functions. Nature conservation requires the full consideration of palaeoecological knowledge in an ecological context, along with the synergistic cooperation of palaeoecologists with neoecologists, anthropologists, and conservation scientists.  相似文献   

8.
We present a multiproxy study of land use by a pre-Columbian earth mounds culture in the Bolivian Amazon. The Monumental Mounds Region (MMR) is an archaeological sub-region characterized by hundreds of pre-Columbian habitation mounds associated with a complex network of canals and causeways, and situated in the forest–savanna mosaic of the Llanos de Moxos. Pollen, phytolith, and charcoal analyses were performed on a sediment core from a large lake (14 km2), Laguna San José (14°56.97′S, 64°29.70′W). We found evidence of high levels of anthropogenic burning from AD 400 to AD 1280, corroborating dated occupation layers in two nearby excavated habitation mounds. The charcoal decline pre-dates the arrival of Europeans by at least 100 yr, and challenges the notion that the mounds culture declined because of European colonization. We show that the surrounding savanna soils were sufficiently fertile to support crops, and the presence of maize throughout the record shows that the area was continuously cultivated despite land-use change at the end of the earth mounds culture. We suggest that burning was largely confined to the savannas, rather than forests, and that pre-Columbian deforestation was localized to the vicinity of individual habitation mounds, whereas the inter-mound areas remained largely forested.  相似文献   

9.
“Political-industrial ecology” has been proposed as an emerging subfield of nature-society geography. In mapping out the landscape of this subfield, this paper develops a typology of three approaches to connecting politics and industrial ecology: (1) Integrative research that incorporates social, political, policy, institutional, and/or spatial considerations into industrial ecology analyses (“politics in industrial ecology”); (2) Complementary research that couples findings or frameworks from industrial ecology with social and political research (“politics and industrial ecology”); and (3) Critical research that examine how values, norms, groups, political relations, or institutions shape the production, interpretation, and usage of industrial ecology knowledge (“politics of industrial ecology”). This broad framing of political-industrial ecology invites contributions from many social sciences, including political ecology, political geography, political economy, sociology, public policy, management, environmental history, and science and technology studies.  相似文献   

10.
Risk assessment and management, are increasingly established as key procedures in dealing with the range of environmental issues at different scales and of different nature. Although at the EU and international policy level requirements for the use of risk assessment and management are being established through emerging policy and legislation, this demand has not been followed with common guidance on how to do so. This has proven to hinder the effective adoption of such processes, and posed a barrier more so in its implementation for large transboundary issues. In this paper is presented a Decision Support System (DSS) designed to provide a common framework and procedure for environmental risk assessment and management. The DSS is web-based and was developed to enable the formalized and more systematic utilization of risk assessment and management procedures in environmental decision making processes, in particular for users such as public authority officials charged with the responsibility of implementing risk management legal and policy obligations, yet which have limited know how in the field of risk. The DSS presented herein enables environmental administrators and decision makers to undertake generic risk assessment and management identifying areas where detailed risk assessment is required, proposing as well as appropriate risk management options. The web DSS was developed and piloted as part of the STRiM project funded by the European Union. Herein are shown results from the web application which has been trailed successfully in four pilot trials addressing risks of forest damage from storms, water pollution from olive mill waste discharges, wetland loss from water abstraction, and damage from flooding.  相似文献   

11.
Two sediment cores from Mauritia flexuosa palm swamps have been studied by pollen and charcoal analysis. The cores Fazenda Cigana (FC) and Terra Indígena Aningal (TIA) were taken from a savanna-forest ecotone area in the Roraima State, northern Brazilian Amazon. Based on 5 radiocarbon dates, these records allow the reconstruction of the vegetation fire and climate dynamics during the past 1550 years. At the FC site was recorded a higher proportion of forest cover, suggesting local wetter climatic conditions favorable for forest expansion, especially by gallery forests, between 1550 and 1400 cal yr BP. Stands of M. flexuosa started to establish on the site indicating sufficient soil moisture. From 1400 to 1050 cal yr BP, forest cover retreated while savanna, and the Mauritia palm swamp expanded considerably. The FC site was marked by savanna and Mauritia cover with a slight increase of forest between ca. 1050 and 900 cal yr BP. From 900 to 300 cal yr BP the savanna and palm swamp taxa became dominant and the forest area decreased. At the TIA site the savanna cover was dominant between 1200 and 1000 cal yr BP. From 1000 to 700 forest expanded while savanna and Mauritia palm swamp reduced. Between 700 and 300 cal yr BP savanna and Mauritia palm swamp increased and forest area decreased. The high amount of charred particles found in the sediments, indicate fires with a marked increase between 1400 to 1000 cal yr BP (FC site) and 700 to 300 cal yr BP (TIA site), and probably caused the retreat of forest cover during these two time intervals. The relatively lower fire activity after 300 cal yr BP until present-day favored the increase of forested area at both TIA and FC sites. The arrival of the European settler and the subsequent introduction of cattle, is suggested as the main reason for the decrease of fire in the study region. The results point the fire caused by indigenous people as the principal controlling factor for forest and savanna dynamics during the past 1550 years.  相似文献   

12.
Between 1970 and 1980 villages adjacent to the Dong Mun Uplands of Northeastern Thailand were transformed from subsistence communities, based on wet rice production, to a cash economy linked to global markets and the national and international political order. Although formally designated reserves had been created on old growth forests, the new economic opportunities encouraged conversion of forests to agriculture. Attracted by a false belief that land was being made available for settlement, immigrants flooded in and cleared forests to plant dryland cash crops using the newly expanded and improved road network to export their products. Social forestry programs may have assisted community development and encouraged agricultural diversification but were insufficient to prevent the contraction of forests, which now remain only as degraded remnants on the steepest slopes and least accessible sites.To some extent the social, political and economic forces have stabilized in Dong Mun and evidence of a new relationship between humans and their forest land is appearing. The Royal Forest Service is largely reconciled to the loss of domain over most of forest reserve and is pursuing a modified management policy that shows some evidence of a shift from an industrial to a post-industrial mode.In recent years, Buddhist monks in forest temples found through the uplands have achieved some effective forest conservation and restoration. Their efforts stem from the Buddhist precepts of the sanctity of all life and a view that forests are places for contemplation and spiritual renewal. Monks have been able to protect and restore some forest land because their views and wishes are far more likely to be honored than laws and demands of government officials. This reflects a broader phenomenon in Thailand where considerable impetus for a contemporary environmental movement has come from religious sources in contrast to the west where it is largely a secular in origin.  相似文献   

13.
The management of fire within landscapes is a topic of increasing contestation. This is particularly the case in relation to the practice of ‘prescribed burning’, which aims to exercise a form of control of wild fires through the application of science-based techniques that putatively reconcile the conservation of biodiversity with the protection of human life and property in particular places. The belief in possibilities to solve environmental problems by scientific approaches and in outcomes that do not involve harm or vulnerabilities is an element of a trend called “Ecological Modernisation” (EM). Various studies have shown how discourses of EM have come to dominate the ways in which many contemporary environmental problems are approached. We argue that highlighting the presentation of such discourses as neutral and non-politicised precludes a critical examination of the ways in which the knowledge claims upon which they rest can be seen to reinforce only particular sets of constructions of the relationship between humans and the natural world. Through an analysis of knowledge claims made in relation to recurring topics such as the use of fire by Indigenous Australians and the adaptation of species to fire, we illustrate that behind the discourse of ecological modernisation sit deeply engrained variations in terms of where people locate vulnerability in relation to the pressing problem of wildfire and fire management. We argue that the depoliticisation of the topic sustains specific types of relationships between people and nature while delegitimising others and obscures the fundamentally different notions about relationships between humans and non-human nature upon which the debate ultimately pivots.  相似文献   

14.
Whilst ecological modernisation theory emphasizes the potential for modern societies to recognize and respond to their environmental impacts by finding new ways of governing environment-economy relations, concepts of policy learning focus on the scope for new forms of environmental policy to be generated within and transferred between different contexts. Within this paper we explore the conceptual and practical linkages between the two areas of debate - a hitherto neglected area in the literature - and we set this discussion in the context of environmental policy-making in Hong Kong. We suggest that the practical relevance of the concepts of ecological modernisation and policy learning depends upon the presence of a reflexive society with rational, responsive institutions. While many theorists assume that such institutions exist, our analysis of policies for water and air quality management in Hong Kong highlights the need for theories to consider the embeddedness of existing institutions and the significance of the capacities for, and the barriers to, change more fully. We find that capacities for some forms of ecological modernisation and policy learning do exist in Hong Kong. However, we argue that the nature of these capacities often limits the potential for change to those local environmental problems that can be addressed through more technically and economically viable forms of policy intervention and that can be easily accommodated within existing political and economic structures. We also conclude that the capacities for ecological modernisation and policy learning that are needed if Hong Kong is to tackle the effects of the trans-boundary environmental problems that it is increasingly encountering have yet to emerge.  相似文献   

15.
Scale, as concept, has featured prominently in political ecology and remains, even if implicitly, a crucial point of analytical reference. Recent studies, drawing from both human geography and ecology, have sought to demonstrate how scales, rather than pre-existing ontologically, are both socially and environmentally produced. Given the different scales through which social and environmental processes occur, the study of society-environment relations can be improved by analysing varying scalar configurations of interaction. This recent and promising methodological corrective would greatly benefit from a dialogue with world-systems approaches, which integrate diverse scale-producing processes and to some extent overlap in scope with political ecology. World-systems perspectives, by focusing on the long-term systemic character of people-environment relations, effectively connect micro- to macro-scale social and ecological processes and explain long-term internal dynamics and interrelations of systems at different scales. Conversely, world-systems approaches could learn much from political ecologists’ consideration of nonhuman processes into understandings of scale and society-environment relations, which has a long tradition in geography, as well as from the more context-sensitive analytical framework brought to those understandings. Case studies are discussed to demonstrate not only how these two perspectives could be integrated, but also how explanations of environmental change can be thereby improved. Combining the two approaches provides the basis for a more ecologically oriented world-systems paradigm and, in political ecology, for greater sensitivity to socially large-scale systemic processes and, given the originally anti-capitalist underpinnings of both paradigms, for more political coherence.  相似文献   

16.
In recent years, there has been heightened interest in creating more environmentally sustainable forms of urban development in China. Central in these greening initiatives has been increased attention on promoting public participation in community-based environmental activities. Focusing on China’s green community initiatives, we examine the production and effects of participation in a state-led development program. Our analysis considers how incentives for program organizers and participants are structured by broader political and economic imperatives facing Chinese cities. We also consider what influence China’s history of neighborhood-based mobilization campaigns had on the meanings and methods of participation in green communities. To understand how urban development processes and memories of mobilization influence participation at the local level, we present two examples of the community greening process from the city of Guangzhou, comparing policy outcomes between a new and older neighborhood. This article seeks to demonstrate that the participatory processes associated with such an urban environmental initiative cannot be adequately understood without reference to earlier participatory practices and broader policy priorities guiding development in Chinese cities.  相似文献   

17.
Jamey Essex 《Geoforum》2008,39(4):1625-1636
The institutions, practices, and discourses of US development policy and foreign assistance are undergoing profound changes. Central to these has been the creation of a new framework for foreign aid, built around a complex taxonomy of developing states and governance issue areas, with geographic and governance categories predicated on notions of state stability and fragility, strategic geopolitical position, and development progress. Given its long-standing position as the primary federal agency responsible for development and foreign aid, the US Agency for International Development (USAID) has played an important role in these policy changes, even as its political status and standing have suffered in recent years. The new framework is beset by contradictions, stemming both from the problematic relationship between development, security, and liberalization in agency rhetoric and strategies, and from intensive restructuring processes affecting USAID’s internal character and external relations. This paper investigates the new framework for foreign aid, linking internal restructuring at USAID to broader trends in state development strategies. I argue that shifts in US development and aid policy - toward emphases on “transformational development” abroad and centralization over strategic decision making domestically, crystallized in the new framework - are based in contradictory understandings of aid deservedness that stem from the tensions between economic and geopolitical aims within the current security-focused US state project of neoliberalization. These contradictions and tensions are displaced onto USAID via the Foreign Assistance Framework.  相似文献   

18.
In order to better understand the dynamics of the forest–savanna mosaic from central Cameroon, we analyzed 13C and 14C profiles of six oxisols: two under forests and four under savannas. The δ13C soil profiles collected in the forests indicate that these environments are stable at least since the mid-Holocene, whereas the areas currently covered by savannas were formerly occupied by more forested vegetations. The 14C dating of organic matter indicate that the late extension of the savannas in central Cameroon date from the Late Holocene, starting from 4000–3500 14C yr BP.  相似文献   

19.
The author outlines the relationships between geography and the study of environmental problems. After WW II when these problems were growing in number and complexity, many geographers turned to the quantitative study of spatial relations and processes, neglecting the ecological aspects of human life on earth. However, recently human and physical geography are turning again to an ecological point of view. In the study of environmental problems, a synthesis of the spatial and the ecological traditions in geography is possible. The spatial aspects of environmental problems and environmental management in a systems-theory framework are the central points in the contribution of geography to an interdisciplinary environmental science.  相似文献   

20.
As part of a collaborative research project created to promote the coexistence of fire, people and biodiversity in central Australia, a case study was conducted on Aboriginal perceptions of fire and its management in the southern Tanami Desert of Central Australia. The Tanami was chosen due to consecutive wildfire events and reported fire conflicts between Aboriginal and pastoral (cattle station) landholders on fire issues. This paper addresses fire issues from the perspective of Warlpiri Aboriginal people in this region. It shows that many Warlpiri hold strong views concerning the use of fire and its management. Elders, in particular, have retained tradition-based knowledge about fire and its effects on the environment. The complex cultural protocols that structure decisions about who burns, when and where are discussed. It is shown that, although there have been dramatic changes to their subsistence economy, Warlpiri still burn for cultural and economic reasons. At the same time, social change has given rise to new fire-related issues, including lack of access to remote areas in order to undertake burning and a decrease in fire knowledge among younger generations. The paper argues that Warlpiri perceptions of fire management, needs and skills must be incorporated in a regional fire management strategy if the cycle of wildfire that follows above average rainfall periods in the Tanami is to be broken. Proper resourcing of Aboriginal people to fire their land in customary ways will enhance Aboriginal livelihoods as well as benefit other stakeholders in the region.  相似文献   

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