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1.
The discussion about the impact of pastoral systems on ecosystems has been profoundly shaped by Hardin’s “tragedy of the commons”
argument that held pastoralists responsible for overgrazing the range. Recent studies have shown that grazing ecosystems are
much more complex and dynamic than was previously assumed and that pastoralists adaptively manage these systems. However,
we still have little understanding how everyday herding affects ecosystems at the landscape level. We conducted a study of
daily herd movements and grazing strategies in a mobile pastoral system in the Logone floodplain, Cameroon. We integrated
GPS/GIS technology, video recordings of animal behavior, and ethnographic methods to develop a more accurate measurement of
grazing pressure that takes into account both livestock densities and grazing behavior. We used the resulting grazing pressure
data to evaluate existing conceptual models of grazing pressure at a landscape level. We found that models that predict that
grazing pressure is skewed towards the direction of water most accurately reflect the situation in the Logone floodplain in
the dry season. However, we found that the higher grazing pressure is not only the result of a higher density of cattle but
also a change in the grazing behavior of animals after watering. Finally, we caution that the models of grazing pressure in
the dry season cannot simply be extrapolated to the landscape level because mobile pastoralists do not remain in one central
place. 相似文献
2.
Leptospirosis is a zoonotic infectious disease of global significance. Political, economic, demographic, ecologic, and other
anthropogenically driven environmental changes have fueled the reemergence of this disease in industrialized and developing
countries, and in both urban and rural settings. We argue that conventional disciplinary, even interdisciplinary, research
methods are not sufficient to elucidate the complex mechanisms and causal relationships among the myriad factors responsible
for infectious disease emergence. To address the significant gaps in the field of leptospirosis, an integrated research agenda
is needed to guide successful public health remediation of the disease. Based on both working group analysis of literature
and newly obtained information, we describe cross-disciplinary collaborative approaches that allow a novel approach to understand
leptospirosis emergence with regard to mountain-to-sea ecosystems in Hawai‘i and other region-specific ecosystems. Leptospirosis
research is a model for how complementary disciplines in the social, cultural, ecological, and biomedical sciences can optimally
interact towards a higher understanding of emerging infectious diseases. 相似文献
3.
Our understanding of disease ecology can be enhanced by the use of spatially explicit models and a biogeographic perspective.
For example, disease emergence is partially a function of shifts in the geographic ranges of pathogens and hosts. Biogeographic
approaches can be used to help us understand the interaction of host and pathogen diversity. Climate change is a global phenomenon
that will require a biogeographic perspective if we are to predict its affect on global disease burden. Studies of disease
ecology can enhance our general understanding of the effects of global change on species’ distributions by providing useful
case studies for developing and testing models. Possibly most important, studies of the spread of pathogens has the promise
of giving us a general law of species’ spread. Currently, biogeography and disease ecology are disciplinary communities with
little overlap. The articles in this special feature are designed to help bridge that gap. 相似文献
4.
The likelihood that coupled dynamical systems will completely synchronize, or become “coherent”, is often of great applied
interest. Previous work has established conditions for local stability of coherent solutions and global attractivity of coherent
manifolds in a variety of spatially explicit models. We consider models of communities coupled by dispersal and explore intermediate
regimes in which it can be shown that states in phase space regions of positive measure are attracted to coherent solutions.
Our methods yield rigorous and practically useful coherence criteria that facilitate useful analyses of ecological and epidemiological
problems. 相似文献
5.
Novel engineered nanomaterials (ENMs) are increasingly being manufactured and integrated into renewable energy generation and storage technologies. Past research estimated the potential impact of this increased demand on environmental systems, due to both the life cycle impact of ENM production and the potential for their direct release into ecosystems. However, many models treat ENM production and use as spatially implicit, without considering the specific geographic location of potential emissions. By not considering geographical context, ENM accumulation or impact may be underestimated. Here, we introduce an integrated predictive model that forecasts likely ENM manufacturing locations and potential emissions to the environment, with a focus on critical environmental areas and freshwater ecosystems. Spatially explicit ENM concentrations are estimated for four case study ENMs that have promising application in lithium‐ion battery production. Results demonstrate that potential ENM exposure from manufacturing locations within buffer zones of sensitive ecosystems would accumulate to levels associated with measured ecotoxicity risk under high release scenarios, underscoring the importance of adding a spatial and temporal perspective to life cycle toxicity impact assessment. This predictive integrated modeling approach is novel to the nanomaterial literature and can be adapted to other regions and material case studies to proactively inform life cycle tradeoffs and decision‐making. 相似文献
6.
There is an urgent need to develop the underlying theory and principles of “sustainability science,” based on an understanding
of the fundamental interactions between nature and humans. This requires a new research and education paradigm that embraces
biocomplexity, integrates the physical, biological, and social sciences, and uses a coupled, human–natural systems approach.
An initiative aligned with this paradigm and approach, and centered on the Hawaiian Island’s unique mountain-to-sea ecosystems,
is developing at the University of Hawai‘i. These ecosystems, extending from upland tropical forests to the fringing coral
reefs, correspond to the roughly wedge-shaped catchments, traditionally called ahupua‘a in the Hawaiian language. Despite the collapse of the ahupua‘a system and, tragically, the Native Hawaiian population, its legacy of ecological and cultural stewardship remains. This legacy,
and the potential of these ecosystems as microcosms for addressing the core questions of sustainability science, has provided
the impetus for a growing number of projects employing a social–ecological systems perspective. An overview of three projects
that employ a “learning community” approach and cultural stewardship perspective inspired by the ahupua‘a system is provided. These include the Ecosystems Thrust Area of Hawai‘i EPSCoR, a U.S. National Science Foundation research
infrastructure program, focused on ecosystem research and monitoring activities; a sustainability curriculum program, Mā lama I Ka ‘Ā ina, of the College of Education; and a project that builds on programs of the Division of Ecology and Health and its affiliated
Asia-Pacific Center for Infectious Disease Ecology, linking ecosystem resilience and infectious diseases. 相似文献
7.
Urban ecological systems are characterized by complex interactions between the natural environment and humans at multiple
scales; for an individual urban ecosystem, the strongest interactions may occur at the local or regional spatial scale. At
the regional scale, external ecosystems produce resources that are acquired and transported by humans to urban areas, where
they are processed and consumed. The assimilation of diffuse human wastes and pollutants also occurs at the regional scale,
with much of this process occurring external to the urban system. We developed the urban funnel model to conceptualize the
integration of humans into their ecological context. The model captures this pattern and process of resource appropriation
and waste generation by urban ecosystems at various spatial scales. This model is applied to individual cities using a modification
of traditional ecological footprint (EF) analysis that is spatially explicit; the incorporation of spatial heterogeneity in
calculating the EF greatly improves its accuracy. The method for EF analysis can be further modified to ensure that a certain
proportion of potential ecosystem services are left for in situ processes. Combining EF models of human appropriation with
ecosystem process models would help us to learn more about the effects of ecosystem service appropriation. By comparing the
results for food and water, we were able to identify some of the potentially limiting ecological factors for cities. A comparison
of the EFs for the 20 largest US cities showed the importance of urban location and interurban competition for ecosystem services.
This study underscores the need to take multiple scales and spatial heterogeneity into consideration to expand our current
understanding of human–ecosystem interactions. The urban funnel model and the spatially heterogeneous EF provide an effective
means of achieving this goal.
Received 17 October 2000; accepted 31 May 2001. 相似文献
8.
The dynamics of two interacting theoretical populations inhabiting a heterogeneous environment are modelled by a system of
two weakly coupled reaction–diffusion equations having spatially dependent reaction terms. Longterm persistence of both populations
is guaranteed by an invasibility condition, which is itself expressed via the signs of certain eigenvalues of related linear
elliptic operators with spatially dependent lowest order coefficients. The effects of change in these coefficients upon the
eigenvalues are here exploited to study the effects of spatial heterogeneity on the persistence of interacting species through
two particular ecological topics of interest. The first concerns when the location of favorable hunting grounds within the
overall environment does or does not affect the success of a predator in predator–prey models, while the second concerns cases
of competition models in which the outcome of competition in a spatially varying environment differs from that which would
be expected in a spatially homogeneous environment.
Received: 9 June 1997 相似文献
9.
A significant fraction of the Earth’s land surface is dominated by bryophytes. Research on carbon and nitrogen budgets of
tundra, boreal, and peatland ecosystems has demonstrated the important role of mosses in understanding global change. Bryophytes
are also habitat to a highly diverse microbiota that plays a key role in the function of these ecosystems. Here we define
the term bryosphere to emphasize the combined role of mosses and their associated organisms in the functioning of ecosystems from local to global
scales. In this minireview, we emphasize the value of the bryosphere as a spatially bounded, whole ecosystem that integrates
aboveground and belowground processes, and we highlight the potential of the bryosphere as a natural model system (NMS) to
assist in the study of environmental change on biodiversity and ecosystem functioning. We propose a formal definition of the
bryosphere, attempt to summarize the current state of knowledge of the bryosphere, and discuss how the bryosphere can be a
complex yet tractable system under an NMS framework. Recent use of the bryosphere as an NMS has shown how alterations in food
web structure can affect ecosystem function in a manner that, although predicted by theory, has remained largely untested
by experiment. An understanding of the biodiversity, ecosystem functioning, and adaptation of the bryosphere can be advanced
by manipulative experiments coupled with a blend of techniques in molecular, physiological, community, and ecosystem ecology.
Although studies described herein have demonstrated the utility of the bryosphere NMS for addressing ecological theory, the
bryosphere is an underutilized system with exceptional promise. 相似文献
10.
Organisms are surrounded by their predators, parasites, hosts, and mutualists, being involved in reciprocal adaptation processes
with such “biotic environment”. The concept of “coevolution”, therefore, provides a basis for the comprehensive understanding
of evolutionary and ecological dynamics in biological communities and ecosystems. Recent studies have shown that coevolutionary
processes are spatially heterogeneous and that traits mediating interspecific interactions can evolve rapidly in natural communities.
Here, I discuss factors promoting the geographic differentiation of coevolutionary interactions, the spatial scales of the
geographic structuring, and the pace of coevolutionary changes, reviewing findings in the arms race coevolution involving
a long-mouthed weevil and its host camellia plant. Evolutionary, ecological, and population genetic studies on the system
illuminated that viewpoints from the aspect of “coevolving biosphere” were important for predicting how ongoing anthropogenic
change in global environment alter the spatiotemporal dynamics of biological communities. 相似文献
11.
Non-native organisms have invaded novel ecosystems for centuries, yet we have only a limited understanding of why their impacts vary widely from minor to severe. Predicting the impact of non-established or newly detected species could help focus biosecurity measures on species with the highest potential to cause widespread damage. However, predictive models require an understanding of potential drivers of impact and the appropriate level at which these drivers should be evaluated. Here, we used non-native, specialist herbivorous insects of forest ecosystems to test which factors drive impact and if there were differences based on whether they used woody angiosperms or conifers as hosts. We identified convergent and divergent patterns between the two host types indicating fundamental similarities and differences in their interactions with non-native insects. Evolutionary divergence time between native and novel hosts was a significant driver of insect impact for both host types but was modulated by different factors in the two systems. Beetles in the subfamily Scolytinae posed the highest risk to woody angiosperms, and different host traits influenced impact of specialists on conifers and woody angiosperms. Tree wood density was a significant predictor of host impact for woody angiosperms with intermediate densities (0.5–0.6 mg/mm3) associated with highest risk, whereas risk of impact was highest for conifers that coupled shade tolerance with drought intolerance. These results underscore the importance of identifying the relevant levels of biological organization and ecological interactions needed to develop accurate risk models for species that may arrive in novel ecosystems. 相似文献
12.
Oceanography and marine ecology have a considerable history in the use of computers for modeling both physical and ecological
processes. With increasing stress on the marine environment due to human activities such as fisheries and numerous forms of
pollution, the analysis of marine problems must increasingly and jointly consider physical, ecological and socio-economic
aspects in a broader systems framework that transcends more traditional disciplinary boundaries. This often introduces difficult-to-quantify,
“soft” elements, such as values and perceptions, into formal analysis. Thus, the problem domain combines a solid foundation
in the physical sciences, with strong elements of ecological, socio-economic and political considerations. At the same time,
the domain is also characterized by both a very large volume of some data, and an extremely datapoor situation for other variables,
as well as a very high degree of uncertainty, partly due to the temporal and spatial heterogeneity of the marine environment.
Consequently, marine systems analysis and management require tools that can integrate these diverse aspects into efficient
information systems that can support research as well as planning and also policy- and decisionmaking processes. Supporting
scientific research, as well as decision-making processes and the diverse groups and actors involved, requires better access
and direct understanding of the information basis as well as easy-to-use, but powerful tools for analysis. Advanced information
technology provides the tools to design and implement smart software where, in a broad sense, the emphasis is on the man-machine
interface. Symbolic and analogous, graphical interaction, visual representation of problems, integrated data sources, and
built-in domain knowledge can effectively support users of complex and complicated software systems. Integration, interaction,
visualization and intelligence are key concepts that are discussed in detail, using an operational software example of a coastal
water quality model. The model comprises components of a geographical information and mapping system, data bases, dynamic
simulation models, and an integrated expert system. An interactive graphical user interface, dynamic visualization of model
results, and a hyper-text-based help-and-explain system illustrate some of the features of new and powerful software tools
for marine systems analysis and modeling. 相似文献
13.
The existence and implications of alternative stable states in ecological systems have been investigated extensively within
deterministic models. However, it is known that natural systems are undeniably subject to random fluctuations, arising from
either environmental variability or internal effects. Thus, in this paper, we study the role of noise on the pattern formation
of a spatial predator–prey model with Allee effect. The obtained results show that the spatially extended system exhibits
rich dynamic behavior. More specifically, the stationary pattern can be induced to be a stable target wave when the noise
intensity is small. As the noise intensity is increased, patchy invasion emerges. These results indicate that the dynamic
behavior of predator–prey models may be partly due to stochastic factors instead of deterministic factors, which may also
help us to understand the effects arising from the undeniable susceptibility to random fluctuations of real ecosystems. 相似文献
14.
Using spatially coupled predator–prey systems as an example of a cyclic ecological system where coexistence depends on oscillations, transient dynamics of models where there are no stable persistent solutions are shown to be a reasonable explanation of persistence over ecological time scales. The parameter values leading to transients within the context of a particular model may be far from parameter values that lead to stable solutions, so transients will need to be explicitly considered in model analysis. Since natural systems with many coupled oscillating species are common, and natural communities are often reset by disturbances or seasonality, transients should play a central role in understanding natural systems. 相似文献
15.
Studies on the Upper Mississippi River, particularly over the last 15 years, have contributed to our understanding of trophic
processes in large rivers. The framework established by earlier population-specific studies, however, cannot be overlooked.
Examination of the feeding habits of fish ranging from planktivores to piscivores gave the first indication that trophic processes
were influenced by the spatial complexity and annual hydrological patterns of river-floodplain ecosystems. Experimental studies,
which have often been considered impossible or impractical in large rivers, demonstrated the potential for biotic controls
of system dynamics through predator–prey and competitive interactions. Such studies have been particularly helpful in understanding
the potential impact of non-native species, including zebra mussels and Asian carp, to biodiversity and secondary production.
Our understanding of riverine ecosystem function expanded greatly as food web studies began the application of a new tool—natural
stable isotopes. Studies employing stable isotopes illustrated how food webs in a number of large rivers throughout the world
are supported by the autochthonous production of microalgae. This study, coupled with other studies testing the prevailing
models of riverine ecosystem function, has brought us to a point of better understanding the nature of river ecosystem functions.
It is through looking back at the earlier studies of fish diet that we should realize that the temporal and spatial complexities
of river ecosystem function must still be addressed more fully. This and a better grasp of the significance of the arrangement
of patches within the riverine landscape will prove beneficial, as we assess the appropriate scale of river rehabilitation
with an eye on how rehabilitation promotes productivity within complex ecosystems, including the Upper Mississippi River. 相似文献
16.
Anticipating critical transitions in spatially extended systems is a key topic of interest to ecologists. Gradually declining metapopulations are an important example of a spatially extended biological system that may exhibit a critical transition. Theory for spatially extended systems approaching extinction that accounts for environmental stochasticity and coupling is currently lacking. Here, we develop spatially implicit two-patch models with additive and multiplicative forms of environmental stochasticity that are slowly forced through population collapse, through changing environmental conditions. We derive patch-specific expressions for candidate indicators of extinction and test their performance via a simulation study. Coupling and spatial heterogeneities decrease the magnitude of the proposed indicators in coupled populations relative to isolated populations, and the noise regime and the degree of coupling together determine trends in summary statistics. This theory may be readily applied to other spatially extended ecological systems, such as coupled infectious disease systems on the verge of elimination. 相似文献
17.
Because it appears that almost all organisms are part of an interdependent metaorganism, an understanding of the underlying host–microbe species associations, and of evolution and molecular underpinnings, has become the new frontier in zoology. The availability of novel high-throughput sequencing methods, together with the conceptual understanding that advances mostly originate at the intersection of traditional disciplinary boundaries, enable biologists to dissect the mechanisms that control the interdependent associations of species. In this review article, we outline some of the issues in inter-species interactions, present two case studies illuminating the necessity of interfacial research when addressing complex and fundamental zoological problems, and show that an interdisciplinary approach that seeks to understand co-evolved multi-species relationships will connect genomes, phenotypes, ecosystems and the evolutionary forces that have shaped them. We hope that this article inspires other collaborations of a similar nature on the diverse landscape commonly referred to as “zoology”. 相似文献
18.
Enclosed, experimental ecosystems (“mesocosms”) are now widely used research tools in ecology. However, the small size, short
duration and often simplified biological and physical complexity of mesocosm experiments raises questions about extrapolating
results from these miniaturized ecosystems to nature. Dimensional analysis, a technique widely used in engineering to create
scale models, employs “compensatory distortion” as a means of maintaining functional similarity in properties and relationships
of interest. An earlier paper outlined a general approach to applying dimensional analysis to the construction and interpretation
of mesocosm experiments (Petersen and Hastings in Am Nat 157:324, 2001). In this paper we use examples, largely drawn from the aquatic literature, to illustrate how dimensional approaches might
be used to maintain key ecological properties. Such key properties include effective habitat size, environmental variability,
vertical and horizontal gradients, and interactions among habitats. We distinguish both continuous and discrete approaches
that can be used to achieve functional similarity through compensatory distortion. In addition to its potential as a tool
for improving the realism of experimental ecosystems, the dimensional approach points towards new options for developing,
testing and advancing our understanding of scaling relationships in nature.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
19.
Restoration ecology is a deepening and diversifying field with current research incorporating multiple disciplines and infusing long‐standing ideas with fresh perspectives. We present a list of 10 recent pivotal papers exemplifying new directions in ecological restoration that were selected by students in a cross‐disciplinary graduate seminar at the University of California, Berkeley. We highlight research that applies ecological theory to improve restoration practice in the context of global change (e.g. climate modeling, evaluation of novel ecosystems) and discuss remaining knowledge gaps. We also discuss papers that recognize the social context of restoration and the coupled nature of social and ecological systems, ranging from the incorporation of cultural values and Traditional Ecological Knowledge into restoration, to the consideration of the broader impacts of markets on restoration practices. In addition, we include perspectives that focus on improving communication between social and natural scientists as well as between scientists and practitioners, developing effective ecological monitoring, and applying more integrated, whole‐landscape approaches to restoration. We conclude with insights on recurrent themes in the papers regarding planning restoration in human‐modified landscapes, application of ecological theory, improvements to restoration practice, and the social contexts of restoration. We share lessons from our cross‐disciplinary endeavor, and invite further discussion on the future directions of restoration ecology through contributions to our seminar blog site http://restecology.blogspot.com . 相似文献
20.
Lagoons in the heavily populated, semi-arid coastal zone of the Southern Mediterranean Region exemplify the conflict between
human utilisation of water and related resources and aquatic ecosystems. Having recognised the requirement to improve understanding
of the functioning of the region’s coastal wetlands, the MELMARINA Project undertook integrated hydro-ecological monitoring
and modelling within lagoons in Morocco, Tunisia and Egypt. This article highlights some key issues regarding environmental
science and management of the region’s coastal lagoons revealed during the course of the project. It stresses the importance
of hydrology as a key control upon lagoon functioning and ecosystem dynamics. Hydrological modifications due to water resource
management schemes are the cause of many recent changes experienced within lagoons. Linkages between water quality, water
availability, human activities and biological characteristics of coastal lagoons are discussed with particular reference to
the controls upon vegetation within the MELMARINA lagoons. A series of methodological advances are reviewed which have potential
for wider application within coastal lagoons. It is suggested that the use of lagoon sediment for environmental reconstruction
can be invaluable, especially when monitoring data are lacking. Recent advances in instrumentation technologies make long-term
continuous monitoring more feasible although these approaches can be combined with more traditional site surveys to provide
wider spatial coverage at the expense of temporal resolution. Wider spatial coverage can also be achieved through the use
of space-borne or aerial remote sensing imagery whilst longer-term trends in site characteristics can be assessed through
historical map analyses. Geographical Information Systems, which facilitate the storage and interrogation of large and varied
datasets, have enormous potential. Similarly, coupled hydro-ecological models can inform understanding of lagoon functioning
and can assess scenarios associated with environmental change or alternative management approaches. The application of integrated,
basin-wide approaches to the management of water resources and aquatic ecosystems in the Southern Mediterranean Region is
advocated. This includes the application of principles from the EU’s Water Framework Directive. Finally, the need to place
management in the context of climate change and associated sea level rise is stressed. Emphasis should be placed on the development
of adaptation strategies designed to minimise the effects of these changes.
Guest editors: J. R. Thompson & R. J. Flower
Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons 相似文献
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