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61.
Recent wetland area trends were estimated from the National Resources Inventory (NRI) for nonfederal rural lands for the period
1982–1987. NRI-based estimates of wetland area for states comprising the conterminous United States were highly correlated
with estimates made by the US Fish and Wildlife Service and with estimates of coastal salt marsh wetlands made by the National
Oceanic and Atmospheric Administration. Net wetland area declined by 1.1% (≈363,200 ha) during the five-year study period.
Conversion to open water, primarily caused by natural flooding in western inland basins, was responsible for altering extensive
wetland areas (≈171,400 ha). Of the human-induced wetland conversions, urban and built-up land was responsible for 48% of
the wetland loss, while agricultural development was indicated in 37% of the converted wetland area. A decrease in rural land,
and increases in both population, and urban and built-up land were associated with wetland loss among states. Potential reasons
for wetland loss were different in 20 coastal states than in 28 inland states. Proportionately, wetland loss due to development
was three times greater in coastal states than inland states, while agriculturally induced wetland losses were similar in
both groups. The proportionate declines of forested vs nonforested wetlands were not significantly different among states. 相似文献
62.
Agricultural land evaluation and site assessment in the United States: An introduction 总被引:2,自引:0,他引:2
Frederick Steiner 《Environmental management》1987,11(3):375-377
The US Soil Conservation Service has developed an agricultural land evaluation and site assessment (LESA) system. The LESA system is being used by the US Department of Agriculture and other federal agencies to implement the Farmland Protection Policy Act of 1981. The LESA system and three case studies from the Pacific North-west are introduced in this article.Scientific Paper no. 7166, College of Agriculture and Home Economics Research Paper. Washington State University, Pullman, Washington. Project no. 0010. 相似文献
63.
Pierre Walther 《Environmental management》1987,11(4):439-446
Integrated resource management (IRM) is currently implemented in many parts of the world. This article promotes a pragmatic interpretation and suggests that idealistic beliefs in the problem-solving capacities of IRM are not justified. Successful implementation and performance of IRM are primarily a function of the historical context into which a project is placed. A comparative analysis of several case studies in Western Canada provides evidence for this argument, and the results can be summarized in a conceptual model about integration in resource management. IRM is interpreted as a process of constructing an objective reality of integration for sectorial management decisions, and this construction involves the transformations of power structures. This article suggests several pragmatic conclusions for IRM practice. 相似文献
64.
Norman J. Thomson 《Environmental management》1986,10(5):591-597
The clearing of over 80% of the native vegetation from Australian agricultural areas has contributed significantly to the degradation classification applied to more than half this land. Soil erosion, siltation, and salinity damage continue to increase yearly. This situation not only threatens the productivity of the farm sector but has contributed to the estimated loss of 78 species of native flora, endangerment of an additional 2206 species, and the loss of 20 species of Australia's marsupials.Private returns diverge from social returns because the action (or inaction) of farmers has an impact upon others, both now and in the future. There is justification, therefore, for the public sector to intervene on behalf of society in an attempt to influence private decision making for the social good. This article argues for increased incentives from the public sector in Australia to encourage the voluntary cooperation of farmers to improve the balance between development and conservation. In contrast to the essentially temporary nature of man-made measures such as flood-mitigating capital works, increasing the area set aside to native bushland offers scope for the permanent stewardship of the resource—land. 相似文献
65.
Robert G. Bailey 《Environmental management》1988,12(1):11-17
As part of the planning process, maps of natural factors are often superimposed in order to identify areas which are suitable or unsuitable for a particular type of resource management. Overlay maps may also be used to identify analysis areas for predictive modeling of resource productivity and ecological response to management. Current interest in applying computer-assisted mapping technology to making overlay maps is drawing attention to geographic information systems for this purpose. The resultant maps, however, may be so inaccurate or unable to capture significant units of productivity and ecological response that they could lead to imperfect or false conclusions. Recommendations are made on how to proceed in light of these problems. 相似文献
66.
Ensuring that new buildings do not interfere with the recreational and protective functions of the natural system and that the buildings will be useful long enough to protect the investment are among long-term solutions to coastal erosion. We propose that coastal cliff management districts be established for management of eroding high relief shorelines. Such districts would include an imminent failure zone, in which bluff retreat is possible at any time; a migration zone, which allows for long-term shoreline retreat; and a stability control zone in which activities affecting bluff erosion are restricted. Procedures are described for delineating these zones based on geomorphic criteria. If these land use controls are implemented, some shorefront development can be accommodated while retaining valuable characteristics of the natural system. 相似文献
67.
Land-cover change in upper Barataria Basin estuary,Louisiana, 1972-1992: increases in Wetland area 总被引:1,自引:0,他引:1
The Barataria Basin, Louisiana, USA, is an extensive wetland and coastal estuary system of great economic and intrinsic value.
Although high rates of wetland loss along the coastal margin of the Barataria Basin have been well documented, little information
exists on whether freshwater wetlands in the upper basin have changed. Our objectives were to quantify land-cover change in
the upper basin over 20 years from 1972–1992 and to determine land-cover transition rates among land-cover types. Using 80-m
resolution Landsat MSS data from the North American Landscape Characterization (NALC) data archive, we classified images from
three time steps (1972, 1985, 1992) into six land-cover types: agriculture, urban, bottomland hardwood forest, swamp forest,
freshwater marsh, and open water. Significant changes in land cover occurred within the upper Barataria Basin over the study
period. Urban land increased from 8% to 17% of the total upper basin area, primarily due to conversions from agricultural
land, and to a lesser degree, bottomland forest. Swamp forest increased from 30% to 41%, associated with conversions from
bottomland hardwood forest and freshwater marsh. Overall, bottomland forest decreased 38% and total wetland area increased
21%. Within the upper Barataria, increases in total wetland area may be due to land subsidence. Based on our results, if present
trends in the reduction of bottomland forest land cover were to continue, the upper Barataria Basin may have no bottomland
hardwood forests left by the year 2025, as it is subjected to multiple stressors both in the higher elevations (from urbanization)
and lower elevations (most likely from land subsidence). These results suggest that changes in the upper freshwater portions
of coastal estuaries can be large and quite different from patterns observed in the more saline coastal margins. 相似文献
68.
Kennett SA 《Environmental management》2002,30(5):0595-0608
Biosphere greenhouse gas (GHG) management consists of preserving and enhancing terrestrial carbon pools and producing biomass
as a fossil fuel substitute. The discussion of this topic has focused primarily on carbon-accounting and project-level issues,
particularly relating to carbon sequestration as a source of emissions credits under the Kyoto Protocol. While international
consensus on these matters is needed, this paper argues that an important domestic policy agenda also deserves attention.
National policies for biosphere GHG management are necessary to bring about large-scale changes in land-use, forestry, and
agricultural practices and can address some of the technical and policy issues that have proven to be particularly problematic
from carbon-accounting and project-level perspectives. These policies should minimize land-use and resource-management conflicts,
account for collateral benefits, and ensure institutional compatibility with existing resource-management regimes. Issues
relating to project permanence, leakage, and transaction costs should also be addressed. A range of policy instruments should
be used and biosphere GHG management should be one component of an integrated approach to environmental and resource management.
Countries promoting biosphere GHG management as an important element of their climate change strategies should be developing
these domestic policies to complement international negotiations and to demonstrate that carbon sequestration and biomass
production can make an effective contribution to the stabilization of atmospheric GHG concentrations. 相似文献
69.
Energy and carbon balances of wood cascade chains 总被引:1,自引:0,他引:1
In this study we analyze the energy and carbon balances of various cascade chains for recovered wood lumber. Post-recovery options include reuse as lumber, reprocessing as particleboard, pulping to form paper products, and burning for energy recovery. We compare energy and carbon balances of chains of cascaded products to the balances of products obtained from virgin wood fiber or from non-wood material. We describe and quantify several mechanisms through which cascading can affect the energy and carbon balances: direct cascade effects due to different properties and logistics of virgin and recovered materials, substitution effects due to the reduced demand for non-wood materials when wood is cascaded, and land use effects due to alternative possible land uses when less timber harvest is needed because of wood cascading. In some analyses we assume the forest is a limiting resource, and in others we include a fixed amount of forest land from which biomass can be harvested for use as material or biofuel. Energy and carbon balances take into account manufacturing processes, recovery and transportation energy, material recovery losses, and forest processes. We find that land use effects have the greatest impact on energy and carbon balances, followed by substitution effects, while direct cascade effects are relatively minor. 相似文献
70.
Mark Dougherty Randel L. Dymond Thomas J. Grizzard Adil N. Godrej Carl E. Zipper John Randolph Christine M. Anderson‐Cook 《Journal of the American Water Resources Association》2006,42(5):1405-1419
ABSTRACT: Long term effects of precipitation and land use/land cover on basin outflow and nonpoint source (NFS) pollutant flux are presented for up to 24 years for a rapidly developing headwater basin and three adjacent headwater basins on the urban fringe of Washington, D.C. Regression models are developed to describe the annual and seasonal responses of basin outflow and IMPS pollutant flux to precipitation, mean impervious surface (IS), and land use. To quantify annual change in mean IS, a variable called delta IS is created as a temporal indicator of urban soil disturbance. Hydrologic models indicate that total annual surface outflow is significantly associated with precipitation and mean IS (r2= 0.65). Seasonal hydrologic models reveal that basin outflow is positively associated with IS during the summer and fall growing season (June to November). NPS pollutant flux models indicate that total and storm total suspended solids (TSS) flux are significantly associated with precipitation and urban soil disturbance in all seasons. Annual NPS total nitrogen flux is significantly associated with both urban and agricultural soil disturbance (r2= 0.51). Seasonal models of phosphorus flux indicate a significant association of total phosphorus flux with urban soil disturbance during the growing season. Total soluble phosphorus (TSP) flux is significantly associated with IS (r2= 0.34) and urban and agricultural soil disturbance (r2= 0.58). In urbanizing Cub Run basin, annual TSP concentrations are significantly associated with IS and cultivated agriculture (r2= 0.51). 相似文献