共查询到20条相似文献，搜索用时 312 毫秒
1.
J. Alcamo G. J. van den Born A. F. Bouwman B. J. de Haan K. Klein Goldewijk O. Klepper J. Krabec R. Leemans J. G. J. Olivier A. M. C. Toet H. J. M. de Vries H. J. van der Woerd 《Water, air, and soil pollution》1994,76(1-2):37-78
This paper presents scenarios computed with IMAGE 2.0, an integrated model of the global environment and climate change. Results are presented for selected aspects of the society-biosphere-climate system including primary energy consumption, emissions of various greenhouse gases, atmospheric concentrations of gases, temperature, precipitation, land cover and other indicators. Included are a “Conventional Wisdom” scenario, and three variations of this scenario: (i) the Conventional Wisdom scenario is a reference case which is partly based on the input assumptions of the IPCC's IS92a scenario; (ii) the “Biofuel Crops” scenario assumes that most biofuels will be derived from new cropland; (iii) the “No Biofuels” scenario examines the sensitivity of the system to the use of biofuels; and (iv) the “Ocean Realignment” scenario investigates the effect of a large-scale change in ocean circulation on the biosphere and climate. Results of the biofuel scenarios illustrate the importance of examining the impact of biofuels on the full range of greenhouse gases, rather than only CO2. These scenarios also indicate possible side effects of the land requirements for energy crops. The Ocean Realignment scenario shows that an unexpected, low probability event can both enhance the build-up of greenhouse gases, and at the same time cause a temporary cooling of surface air temperatures in the Northern Hemisphere. However, warming of the atmosphere is only delayed, not avoided. 相似文献
2.
中国农业温室气体排放量测算及影响因素研究 总被引：3，自引：0，他引：3
农业生产过程所产生的温室气体在全球生产活动温室气体排放总量中占有很大比例,因此对农业温室气体的排放量进行测算并分析其影响因素,对实现农业节能减排有重要意义。本文基于1993―2011年中国农业生产的相关统计数据,借鉴前人关于农业生产中各种温室气体排放源排放系数的研究成果,测算了中国农业生产过程中的CH4、N2O和CO2排放量,并分析了影响因素。结果表明,CH4排放量基本平稳波动不大,N2O排放量从1993年的93.21万t波动增加到2011年的120.51万t,农业生产资料CO2排放量由15 626.98万t增加到31 258.10万t。种植业CO2排放主要分为土壤排放和生产资料排放,土壤CO2排放与大气温度、土壤温度、地表温度和土壤水分有关,生产资料CO2排放主要是由化肥和农药造成的;种植业CH4、N2O排放原因较为复杂,还有待进一步研究;动物肠道发酵CH4、N2O排放的影响因素主要取决于动物种类、饲料特性、饲养方式和粪便管理方式等。 相似文献
3.
This paper describes the IMAGE 2.0 model, a multi-disciplinary, integrated model designed to simulate the dynamics of the global society-biosphere-climate system. The objectives of the model are to investigate linkages and feedbacks in the system, and to evaluate consequences of climate policies. Dynamic calculations are performed to year 2100, with a spatial scale ranging from grid (0.5°×0.5° latitudelongitude) to world regional level, depending on the sub-model. The model consists of three fully linked sub-systems: Energy-Industry, Terrestrial Environment, and Atmosphere-Ocean. The Energy-Industry models compute the emissions of greenhouse gases in 13 world regions as a function of energy consumption and industrial production. End use energy consumption is computed from various economic/demographic driving forces. The Terrestrial Environment models simulate the changes in global land cover on a gridscale based on climatic and economic factors, and the flux of CO2 and other greenhouse gases from the biosphere to the atmosphere. The Atmosphere-Ocean models compute the buildup of greenhouse gases in the atmosphere and the resulting zonal-average temperature and precipitation patterns. The fully linked model has been tested against data from 1970 to 1990, and after calibration can reproduce the following observed trends: regional energy consumption and energy-related emissions, terrestrial flux of CO2 and emissions of greenhouse gases, concentrations of greenhouse gases in the atmosphere, and transformation of land cover. The model can also simulate long term zonal average surface and vertical temperatures. 相似文献
4.
Mark G. Johnson Elissa R. Levine Jeffrey S. Kern 《Water, air, and soil pollution》1995,82(3-4):593-615
In this paper we describe the accumulation of soil organic matter (SOM) during pedogenesis and the processes that can lead to the emission of greenhouse gases (CO2, CH4, N2O) to the atmosphere via SOM decomposition and denitrification. We discuss the role of management on SOM accumulation and loss, and the potential for controlling emission or comsumption of greenhouse gases by soils. We conclude that under current climate conditions there are global scale opportunities to reduce greenhouse gas emissions from soils and increase the indirect sequestration of greenhouse gases in soils through improved soil management. 相似文献
5.
K.A. Smith 《Soil Use and Management》1999,15(2):71-75
Abstract. Over 170 countries have ratified the UN Framework Convention on Climate Change (UNFCCC) which aims at ‘the stabilisation of greenhouse gases in the atmosphere at a level that will prevent dangerous anthropogenic interference with the climate system’. The Kyoto Protocol, signed in 1997, commits the developed (‘Annex 1′) countries to a reduction in gaseous emissions. The global increase in atmospheric CO2, the main greenhouse gas, comes mainly from fossil fuels (6.5 Gt C yr?1), together with about 1.6 Gt C yr?1 from deforestation. The atmospheric increase is only 3.4 Gt C yr?1, however, due to a net sink in terrestrial ecosystems of about 2 Gt C yr?1, and another in the oceans. Increasing net carbon sequestration by afforestation of previously non-forested land is one way of reducing net national emissions of CO2 that is permitted under the Kyoto Protocol. Future modifications may also allow the inclusion of carbon sequestration brought about by other forestry and agricultural land management practices. However, associated changes in net fluxes of two other greenhouse gases identified in the Protocol — nitrous oxide (N2O) and methane (CH4) — will have to be taken into account. Growth of biomass crops can increase N2O emissions, and drainage of wetlands for forestry or agriculture also increases them, as well as emissions of CO2, while decreasing those of CH4. The problems of how to quantify these soil sources and sinks, to maximize soil C sequestration, and to minimize soil emissions of CH4 and N2O, will present a major scientific challenge over the next few years — one in which the soil science community will have a significant part to play. 相似文献
6.
Kentaro Hayashi Takeshi Tokida Masako Kajiura Yosuke Yanai Midori Yano 《Soil Science and Plant Nutrition》2013,59(1):2-33
Croplands are an important source of atmospheric methane (CH4) and nitrous oxide (N2O), both potent greenhouse gases. Reduction of cropland CH4 and N2O emissions is expected to mitigate climate change. However, large uncertainty remains in the assessment and prediction of these emissions, which prevents us from establishing appropriate mitigation options and strategies. The uncertainty is attributed mainly to the high spatiotemporal variability in emissions (e.g., emission spikes of N2O). Understanding and quantifying how hotspots of CH4 and N2O production in soil and then hot moments of their emissions occur would help reduce the uncertainty. This review focuses on soil–plant systems, particularly the rhizosphere, as possible hotspots of production and consumption of CH4 and N2O. It is well known that the rhizosphere controls CH4 emission strongly, though each process of production and consumption remains to be quantified. On the other hand, surprisingly little attention has been paid to N2O, besides the fact that plant roots strongly control nitrification and denitrification. We review the current knowledge of cropland CH4 and N2O emissions, and conclude that soil–plant interactions strongly affect cropland emissions of both gases, in which functions of plant roots affecting biogeochemical factors (e.g., availability of oxygen, labile organic carbon and inorganic nitrogen) in the rhizosphere and phenological changes are particularly important. In relation to the status of current knowledge, we discuss future research needed. 相似文献
7.
As a Party to the United Nations Framework Convention on Climate Change, Israel is committed to develop a national inventory of anthropogenic emissions and removals of greenhouse gases. This paper presents the national inventory, which was developed according to the guidelines of the Intergovernmental Panel on Climate Change (IPCC). The inventory includes the following sectors: energy, industrial processes, agriculture, forestry and waste. In this paper, only the inventory of the direct greenhouse gases (CO2, CH4 and N2O) is presented. Emissions of these gases were converted to CO2 equivalent emissions by means of their Global Warming Potentials (a measure of the radiative effects of the different gases relatively to CO2). CO2 emissions from burning fossil fuels to produce energy are by far the largest source (50 million tons in 1996). The contribution of methane emissions from decomposition of landfilled municipal solid waste is second in importance (8 million tons of CO2 equivalent). Industrial processes emit about 2 million tons CO2 equivalent, the most important process being cement production. Agricultural emissions amount to about 2 million tons CO2 equivalent and are due to soil emissions of nitrous oxide, methane emissions from enteric fermentation in domestic livestock and N2O and CH4 emissions from animal waste management. Although most forests in Israel are in a growing stage and atmospheric CO2 is therefore removed to form biomass, this removal amounts to 0.4 million tons only and is very small as compared to emissions from other sectors. On a per capita basis, Israel's emissions of CO2 from fuel combustion are not far behind those of some of the most developed countries. 相似文献
8.
《Agricultural and Forest Meteorology》2007,142(2-4):270-277
Globally, CO2, CH4 and N2O, contribute 60%, 15% and 5%, respectively, to the anthropogenic greenhouse effect. Atmospheric CO2, CH4 and N2O are currently increasing by 0.5%, 1.1% and 0.3% per year, respectively. This paper reviews studies on greenhouse gas emission and mitigation measures in China in recent years. CH4 emissions originate mainly from rice paddy fields, and are determined by soil characteristics, e.g., temperature, water content, pH and Eh conditions, and by land and crop management, e.g., land use, rice varieties and fertilizer application. Rice paddies emit N2O in addition to CH4, however, the N2O and CH4 emission patterns are quite different. Fertilization practices and field water conditions are major factors that control N2O emissions. In order to minimize net greenhouse gas emissions from agricultural production systems, either sources of emissions must be reduced, or agricultural greenhouse gas sinks must be enhanced or newly created. Because the effects of greenhouse gas mitigation measures on each greenhouse gas are different, specific practices must be developed and adopted for the various gases. This paper discusses some promising greenhouse gas mitigation strategies to reduce net emissions from agroecosystems in China. 相似文献
9.
Madeline Thurlow Ken-ichi Kanda Haruo Tsuruta Katsuyuki Minami 《Soil Science and Plant Nutrition》2013,59(2):371-375
Abstract Methane (CH4) is one of the most abundant organic gases in the atmosphere. Recently the importance of CH4 as a greenhouse gas has been recognized and studies have been carried out to assess its contribution to global warming. Although the rate of increase has slowed down in the last decade (Steel et al. 1992; Rudolph 1994), the results from some of these studies have shown that the atmospheric concentration of CH4 is increasing at a rate estimated to be approximately 1% per year (Rowland 1991; Blake and Rowland 1988; Bolle et al. 1986; Graedel and McRae 1980). Clearly it is important to identify sources and sinks of CH4, in both terrestrial and oceanic ecosystems, in order to estimate global methane budgets (Cicerone and Oremland 1988). 相似文献
10.
基于DNDC模型模拟江汉平原稻田不同种植模式条件下温室气体排放 总被引：3，自引：0，他引：3
稻田被认为是温室气体CH_4和N_2O的主要排放源之一。湖北省江汉平原地区水稻常年种植面积约8×105 hm2,占湖北省水稻种植面积的40%左右。研究江汉平原地区稻田温室气体排放特征,对于评估区域稻田温室气体排放以及稻田温室气体减排具有重要意义。目前,DNDC模型已被广泛应用于模拟和估算田间尺度的温室气体排放,DNDC模型与地理信息系统(Arc GIS)结合,可进行区域尺度的温室气体排放模拟与估算。本研究以湖北省典型稻作区江汉平原为研究区域,运用DNDC模型模拟和估算江汉平原稻田区域尺度的温室气体排放。设置大田定点观测试验,监测中稻-小麦(RW)、中稻-油菜(RR)、中稻-冬闲(RF)3种种植模式下稻田温室气体CH_4和N_2O的周年排放特征。通过田间观测值与DNDC模拟值的比较进行模型验证,并利用获取DNDC模型所需的气象、土壤、作物及田间管理等区域数据,模拟江汉平原稻田不同种植模式下温室气体CH_4和N_2O的排放量。田间试验表明,江汉平原稻田RW、RR和RF模型的CH_4排放通量为-2.80~39.78 mg·m-2·h-1、-1.74~42.51 mg·m-2·h-1和-1.57~55.64 mg·m-2·h-1,N_2O周年排放通量范围分别为0~1.90 mg·m-2·h-1、0~1.76mg·m-2·h-1和0~1.49 mg·m-2·h-1;CH_4排放量RW和RR模式显著高于RF模式,N_2O排放量为RF显著低于RW和RR模式。模型验证结果表明,不同种植模式温室气体排放实测值与模拟值比较的决定系数(R2)为0.85~0.98,相对误差绝对值(RAE)为8.29%~16.42%。根据DNDC模型模拟和估算的结果,江汉平原区域稻田CH_4周年的排放量为0.292 9 Tg C,N_2O周年的排放量为0.009 2 Tg N,不同种植模式稻田CH_4排放量表现为RWRRRF,N_2O排放量表现为RWRFRR,增温潜势(GWP)表现为RWRRRF。不同地区稻田CH_4排放量表现为监利县荆门市公安县天门市仙桃市洪湖市松滋市汉川市潜江市石首市荆州市江陵县赤壁市嘉鱼县,N_2O排放量表现为监利县荆门市公安县洪湖市仙桃市天门市汉川市潜江市松滋市荆州市江陵县赤壁市石首市嘉鱼县。本研究结果表明DNDC模型能较好地应用于模拟江汉平原稻田温室气体排放,RR和RF模式相比RW模式可有效减少温室气体CH_4和N_2O的排放。 相似文献
11.
《Soil Science and Plant Nutrition》2013,59(5):668-677
Abstract The scenarios for conventional puddling and no-tilling rice (Oryza sativa L.) cultivation were compared in terms of greenhouse gas (GHG) emissions from paddy fields, fuel consumption and manufacturing of invested materials using a life cycle inventory (LCI) based analysis. Only the differences between the scenarios were examined. The no-tilling scenario omitted both tilling and puddling, but included spraying of a non-selective herbicide and used a transplanter equipped with a rotor. Fertilization was a basal single application of controlled release fertilizer in nursery boxes for all scenarios. After transplanting, there were no differences in machine work, invested materials or rice yields between the scenarios. The no-tilling scenario saved on fuel consumption, totaling carbon dioxide (CO2) output of 42 kg ha?1, which was equal to the 6% reported GHG emissions from fuel consumption by operating machines during rice production in Japan. Methane (CH4) and nitrous oxide (N2O) emissions from the paddy fields were also monitored and compared for the scenarios. Methane has a major effect on global warming as part of the GHG emitted from paddy fields. The cumulative CH4 emissions from the no-tilling cultivation were 43% lower than those from conventional puddling cultivation because the plow layer was more oxidative in no-tilling cultivation. The N2O emissions were not significantly different between the cultivation scenarios. There were no significant differences in soil respiration, soil carbon contents or straw yields between the cultivation scenarios. The effect of tillage on CO2 flux in the paddy fields did not seem to be significant in this study. Consequently, the GHG emissions from the no-tilling field counted as CO2 using global warming potentials were 1,741 kg CO2 ha?1 lower than those from the conventional puddling field. In conclusion, no-tilling rice cultivation has the potential to save 1,783 kg CO2 ha?1 calculated using the sum of fuel consumption and GHG emissions from paddy fields. No-tilling rice cultivation is considered to be environmentally friendly agriculture with respect to reducing GHG emissions. 相似文献
12.
Exchange of greenhouse gases between soil and atmosphere: interactions of soil physical factors and biological processes 总被引：34，自引：0，他引：34
K. A. Smith T. Ball F. Conen K. E. Dobbie J. Massheder & A. Rey 《European Journal of Soil Science》2003,54(4):779-791
This review examines the interactions between soil physical factors and the biological processes responsible for the production and consumption in soils of greenhouse gases. The release of CO2 by aerobic respiration is a non‐linear function of temperature over a wide range of soil water contents, but becomes a function of water content as a soil dries out. Some of the reported variation in the temperature response may be attributable simply to measurement procedures. Lowering the water table in organic soils by drainage increases the release of soil carbon as CO2 in some but not all environments, and reduces the quantity of CH4 emitted to the atmosphere. Ebullition and diffusion through the aerenchyma of rice and plants in natural wetlands both contribute substantially to the emission of CH4; the proportion of the emissions taking place by each pathway varies seasonally. Aerated soils are a sink for atmospheric CH4, through microbial oxidation. The main control on oxidation rate is gas diffusivity, and the temperature response is small. Nitrous oxide is the third greenhouse gas produced in soils, together with NO, a precursor of tropospheric ozone (a short‐lived greenhouse gas). Emission of N2O increases markedly with increasing temperature, and this is attributed to increases in the anaerobic volume fraction, brought about by an increased respiratory sink for O2. Increases in water‐filled pore space also result in increased anaerobic volume; again, the outcome is an exponential increase in N2O emission. The review draws substantially on sources from beyond the normal range of soil science literature, and is intended to promote integration of ideas, not only between soil biology and soil physics, but also over a wider range of interacting disciplines. 相似文献
13.
Peatlands are significant sources of the important greenhouse gas CH4 and generally known as sinks for atmospheric CO2 through peat accumulation. Accurate measurements of the subsurface concentrations of these gases are of pivotal importance for experimental studies improving our understanding of the dynamics and controls on the exchanges of these gases between peat soils and the atmosphere. In this paper we first briefly outline examples of different probe-based techniques for the determination of subsurface gas concentrations and thereafter we document the development and testing of two different membrane probe systems. Finally we discuss a few applications of the probes and show some results obtained by testing them in the laboratory. 相似文献
14.
不同耕作条件下豆麦双序列轮作农田土壤温室气体的排放及影响因素研究 总被引：2，自引：0，他引：2
为了研究耕作措施对双序列轮作农田土壤温室气体的排放及影响, 采用CO2分析仪、静态箱 气相色谱法在陇中黄土高原半干旱区对传统耕作不覆盖、免耕不覆盖、免耕秸秆覆盖和传统耕作+秸秆还田4种耕作措施下豆麦双序列轮作农田土壤温室气体(CO2、N2O和CH4)的排放及影响因素进行了连续测定和分析。结果表明: 测定期内4种耕作措施下农田土壤均表现为CO2源、N2O源和CH4净吸收汇; 除传统耕作不覆盖措施, 其他3种耕作措施不同程度地减少了2种轮作序列土壤的N2O排放通量, 并显著增加了土壤对CH4的吸收。CO2和N2O的排放通量分别与地表、地下5 cm处、地下10 cm处的土壤温度呈极显著和显著正相关关系, 相关系数分别为0.92**和0.89**、0.95**和0.91**、0.77*和0.62*; 而CH4吸收通量与不同地层的温度之间无明显的相关关系; CO2和CH4的通量与0~5 cm、5~10 cm的土壤含水量均呈显著正相关关系, 相关系数分别为0.69*和0.72*、0.77*和0.64*, 而与10~30 cm土壤含水量无明显相关关系; N2O排放通量与各层次的土壤含水量之间均呈不显著负相关关系。对2种轮作序列各处理下土壤中排放的3种温室气体的增温潜势计算综合得出: 4种耕作措施中, 免耕不覆盖处理可相对减少土壤温室气体的排放量, 进而降低温室效应。 相似文献
15.
中国自然湿地甲烷排放: 1995-2004年研究总结 总被引：2，自引：0，他引：2
From studies undertaken during 1995-2004, annual budgets of CH4 emissions from natural wetlands and its temporal and spatial variations were examined throughout China, and various factors influencing CH4 emissions were also evaluated. The seasonal variation in CH4 emissions that increased with increasing plant growth reached its peak in August;decrease in the emissions was found in freshwater marshes but not in peatlands. Emissions were mainly controlled by temperature and depth of standing water. Low CH4 emissions at the early plant growing stages were not because of deficiency of organic C for CH4 production but because of low temperatures. Low temperatures not only reduced CH4 production but also stimulated CH4 oxidation by lowering the activity of other aerobic microbes which left more O2 in the rhizosphere for methanotrophs. Low summer temperatures (below 20 ℃) in the Qinghai-Tibetan Plateau lowered CH4 production and CH4 emission resulting in little or no seasonal variation of emissions. Diel and spatial variation in CH4 emissions depended on plant species. For plants that transport CH4 using the pressure-driven convective through-flow mechanism, diel variation in CH4 emissions was governed by diel variation of solar energy load (that produces temperature and vapor pressure differences within various plant tissues) and stomatal conductance. For plants that transport gases using the molecular diffusion mechanism only, the diel variation of CH4 emissions was because of differences in the magnitude of O2 produced through photosynthesis and then delivered into the rhizomes and/or rhizosphere for CH4 oxidation. Emergent plants could transport more CH4 than submerged plants because the former transport CH4 directly into the atmosphere rather than into water as do submerged plants where CH4 can be further be oxidized during its diffusion from water to the atmosphere. Emergent plants with high gas transport capacity could not only transport more CH4 into the atmosphere but also live in deeper water, which in turn would inundate more plant litter, resulting in increased availability of C for CH4 production. Annual CH4 emission from natural wetlands in China was estimated to be 1.76 Tg, up to 1.17 Tg of which was emitted from freshwater marshes. CH4 emission from freshwater marshes mainly occurred during the growing season and less than 8% was released during the freeze-thawing period despite the fact that thawing efficiently released CH4 fixed in ice column into the atmosphere. 相似文献
16.
氢醌、双氰胺组合影响稻田甲烷和氧化亚氮排放研究进展 总被引：12，自引：0，他引：12
稻田是大气中CH4和N2O的重要来源。大量氮肥的施入不仅影响稻田CH4和N2O排放,且易造成NH3挥发、NO2-和NO3-淋溶及N2O、N2等形式的氮损失。脲酶抑制剂和硝化抑制剂通过缓解尿素水解及抑制硝化反硝化反应减少稻田N2O排放量,但对稻田CH4产生排放的影响报道不一。脲酶抑制剂氢醌(HQ)和硝化抑制剂双氰胺(DCD)是近年来研究较多的组合。本文试图在前人研究的基础上,综述HQ和DCD的基本性质及作用机理,总结HQ/DCD组合在稻田生态系统的应用状况、使用效果及存在问题,并特别讨论了HQ/DCD施用对稻田CH4排放的影响机理,旨在为合理使用脲酶/硝化抑制剂、有效减缓稻田温室气体排放和提高氮肥利用率等方面提供理论依据。 相似文献
17.
水分类型对土壤排放的温室气体组成和综合温室效应的影响 总被引：34，自引：2，他引：34
实验室研究表明,土壤排放出的温室气体（ＣＯ２、ＣＨ４和Ｎ２Ｏ）组成及总理显著地受土壤水分类型和施用秸秆的影响。连续淹水条件下,土壤仅排放微理的Ｎ２Ｏ,但排放出大量的Ｃ睡Ｃ敢条件下,土壤不排放Ｃ上键合的但排放出大量的Ｎ２Ｏ;虽然淹水的土壤排水促进Ｎ２Ｏ排放,但显著抑制ＣＨ４的排放,淹水好气交替处理的土壤其排放的ＣＯ２、ＣＨ４和Ｎ２Ｏ均在好气和连续淹水之间。根据各种温室产生温室效应的相对潜力,计算土壤 相似文献
18.
《Communications in Soil Science and Plant Analysis》2012,43(13):1604-1614
Use of inorganic fertilizers and manures are known to result in the release of greenhouse gases (GHG) to the atmosphere, and rainfall events can also increase GHG emissions from soils. The objective of this study was to examine how the time between fertilizer or manure application and the first rainfall event affects carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes. Swine manure, poultry litter, and urea were surface applied to plots. Rainfall was simulated 1, 4, 8, 15, or 29 days after application. Gas fluxes were determined before and after each rainfall simulation. Postrain CO2 fluxes were the greatest from poultry litter at 4 to 8 days after fertilization, and all fertilizer treatments produced similar N2O emissions with a peak 4 days after fertilization. These data seem to indicate that if manures are applied during drier periods of the year, GHG emissions can be minimized, in addition to reducing nutrient runoff losses. 相似文献
19.
20.
G. Zuidema G. J. van den Born J. Alcamo G. J. J. Kreileman 《Water, air, and soil pollution》1994,76(1-2):163-198
This paper describes two global models: (1) an Agricultural Demand Model which is used to compute the consumption and demand for commodities that define land use in 13 world regions; and, (2) a Land Cover Model, which simulates changes in land cover on a global terrestrial grid (0.5° latitude by 0.5° longitude) resulting from economic and climatic factors. Both are part of the IMAGE 2.0 model of global climate change. The models have been calibrated and tested with regional data from 1970–1990. The Agricultural Demand Model can approximate the observed trend in commodity consumption and the Land Cover Model simulates the total amount of land converted within 13 world regions during this period. Some degree of the spatial variability of deforestation has also been captured by the simulation. Applying the model to a “Conventional Wisdom” scenario showed that future trends of land conversions could be strikingly different on different continents even though a consistent scenario (IS92a from the IPCC) was used for assumptions about economic growth and population. Sensitivity analysis indicated that future land cover patterns are especially sensitive to assumed technological improvements in crop yield and computed changes in agricultural demand. 相似文献