基于生态系统服务的罗源湾围填海方案的经济效益评价

基于可持续发展角度,运用环境经济学理论和方法,建立效益和费用评估模型.按照生态系统服务理论将围填海造成的生态损失货币化,作为经济成本的一部分,参与围填海方案经济效益评价.本文对罗源湾多个围填海方案进行综合评价,并对其进行排序,寻求适宜方案.     

Use of particle-size data to predict potential pelagic-fish yields of some southern African areas

A particle-size spectrum model is used to estimate standing stocks of some pelagic fish from measurements of phytoplankton chlorophyll in two exploited regions in southern Africa (southern Benguela and off South West Africa/Namibia) and in two unexploited regions (the Agulhas Bank and off the eastern Cape Province). The model is based on the assumption that equal biomasses occur in logarithmically equal size classes in the pelagic marine environment. Phytoplankton, with an equivalent spherical diameter ranging from 1 to 128 μm, occupy 21 size classes on the logarithmic scale. Two different size ranges are assumed for some commercial, pelagic fish species, equivalent to exploitation with two different purse-seine mesh sizes. A mesh of 12,7 mm would catch 8 size classes of pilchard, horse mackerel and anchovy whereas a mesh of 32 mm would catch only 3,3 size classes of pilchard and horse mackerel. From the model, the potential biomass of these commercial pelagic fish is estimated, after allowing for the presence of other commercial and non-commercial fish and other taxa in the exploited size range. Total pelagic fish production is estimated by assuming constant turnover rates of 1·y^?1 and 1,5·y^?1 when exploited with 32 and 12,7 mm mesh nets respectively. Consideration of the maximum and mean reported catches in the exploited areas indicates that only some 25 per cent of pelagic fish production is exploitable by man. On this basis, the unexploited Agulhas Bank region may yield some 400 000 metric tons (wet) of pelagic fish of the species considered, and the East Coast region some 90 000 tons. Exploitation in these regions cannot be recommended, because the Agulhas Bank is an important spawning ground for many pelagic species, and the fish in both regions probably act as a reserve buffer for the heavily exploited pelagic resource of the Western Cape.     

A parsimonious crop-water productivity index: an application to Brazil

Reducing poverty in rural areas of developing countries requires sustained and sustainable increases in agricultural water productivity. However, aside from traditional measures of precipitation, little is known about water available to farmers or how productively they use it. We present a crop-water productivity index (a ratio of the value of annual crop production to a dimensionless potential water availability index) for large water basins using readily available low-resolution data. The index is transferable, permits direct inter-basin comparisons, and is simple to calculate. We calculate the index for each municipality in the São Francisco river basin in Brazil. No clear patterns linking water availability and value of agricultural output are evident, even though clusters of municípios with high- and low-crop-water productivity emerge, and the former may be useful in guiding policies aimed at increasing water productivity. Finally, analyses of the effects of information uncertainty on the crop-water productivity index suggest that the returns to agricultural investments in certain places in the São Francisco river basin are more risky than others. Improvements in data quality and quantity can help refine estimates of the index and reduce their uncertainty.     

土地利用变化对区域生态系统服务价值的影响——以北京市为例

以北京东北3个区(县)为例,利用从1996年和2005年TM影像中获取的土地利用数据,参照3种典型的生态系统服务价值系数,对比研究该区域的土地利用结构与生态系统服务价值的变化及其相互关系。结果表明:(1)1996—2005年研究区的土地利用变化十分剧烈。耕地变化最明显,共减少264.38 km2,水域和未利用地分别减少72.19,0.17 km2,林地、草地、建设用地面积则分别增加63.76,19.94,253.05 km2。(2)区域总生态系统服务价值在1996—2005年呈下降趋势,依据3种价值系数计算分别下降5.22,3.68,36.49亿元,且离城区中心越远,生态系统服务价值下降越快。(3)在快速城市化进程中,建设用地面积增加,耕地、水域面积减少是研究区生态系统服务价值大幅下降的主要因素。     

我国现行农用地评价体系比较研究

对新中国农用地评价研究进行分析,认为中国现行农用地评价体系有农业部的耕地质量评价体系和国土资源部的农用土地分等定级估价体系两大类.两大体系在评价的目标、内容、指标和方法体系上存在着区别,但最终目标都是实现农用地资源由"数量管理"向"数量、质量和生态"并重管理的转变,实现土地资源的环境友好利用.新时期,在农用地流转的背景下,通过论述比较两大评价体系,指出现行评价体系存在的问题,并给予展望.     

新疆建设国家级四大农产品基地前景分析

新疆水、土、光、热等自然资源的特殊组合,适宜构建多样化的绿洲农业生态系统。结合新疆实际,如何将农业资源优势转化为经济优势,是当前新疆经济转型初期必须认真考虑的问题。对国家研究新疆建设棉花、粮食、特色林果业和畜产品四大基地的背景下对其现状及优劣势,并综合政策、管理、资源和技术等多因素提出了基地建设的前景和应采取的措施。     

塔里木盆地北缘绿洲土地利用与生态系统服务价值的时空变化研究——以渭干河-库车河三角洲绿洲为例

生态系统服务价值的研究是目前生态学研究的热点之一。应用Costanza生态系统服务价值计算公式,采用谢高地等人的中国陆地生态系统单位面积生态服务价值表,分析了1996—2004年渭干河-库车河三角洲绿洲土地利用的时空变化,并计算由此导致的生态系统服务价值及其结构的时空变化,结果表明:①1996—2004年,渭干河-库车河三角洲绿洲总ESV增加,但生态系统服务价值结构变化较大,生态系统提供某些单项服务的功能相对减弱。②1996—2004年,原材料服务功能价值比例上升最多,废物处理服务功能价值比例下降最多。③1996—2004年,渭干河-库车河三角洲绿洲各县生态系统服务价值结构都发生了不同程度的变化。库车县、沙雅县、新和县水源涵养、废物处理、娱乐休闲服务功能价值比例均减少,其中水源涵养服务功能价值比例下降最多。④敏感性分析表明,ESV对生态价值系数缺乏弹性,研究结果可信,说明本研究采用的谢高地生态价值系数是合理的。     

The direct and indirect impacts of population growth and economic development on maize (Zea mays L.) diversity in highland Guatemala

This paper discusses the impacts of population growth and economic development on maize diversity in highland Guatemala. In the context of this discussion, economic development specifically refers to the recent expansion of the non-traditional agricultural exports (NTAEs). Population growth and economic development (i.e. NTAEs) are linked because as land has become scarce in highland Guatemala, due to the poor distribution of land resources and rapid population growth over the past 50 years, many farmers have turned to non-traditional economic strategies such as new crops that produce more income per unit of land. These new crops have improved the economic conditions of many farming families, but it has come at a cost regarding the maintenance of local maize varieties and household food security.     

中国农业产业化龙头企业空间分布特征——以国家级重点龙头企业为例

根据880家国家级农业产业化重点龙头企业地理位置、主营业务等资料,利用相关分析、生态分布格局理论等方法,分析了龙头企业在宏观、微观地域及分行业空间布局特征。结果表明：①龙头企业以东部地区聚集为主,西部地区比重有一定提高,东部地区比重有波动;农业发展规模、经济发展水平较高省份聚集企业多,一省农产品丰富度与其龙头企业数相关性亦很显著;②龙头企业在各省内分布聚集程度不一,总体都以聚集为主,尤其以省会城市或中心城市聚集居多。但河北、浙江省内呈均匀分布;③在县级区域,存在一些龙头企业聚集县、专业化县,东部地区聚集县多,中部地区专业化程度高,西部地区特色产业聚集;④划定的17类龙头企业行业,聚集程度大体可分为四类,但总体上对原料依赖行业聚集程度高,对市场依赖行业聚集程度低。     

Ecological evolution across the Permian/Triassic boundary at the Kangjiaping Section in Cili County,Hunan Province,China

The stratigraphic sequence of calcimicrobialite facies at the Permian-Triassic (P/Tr) boundary has well recorded the biotic and environmental transition across the end-Permian catastrophic events. The biostratigraphy, microfacies, carbon isotopes, and fossil records across the P/Tr boundary have been studied at the Kangjiaping Section in Cili County, Hunan Province. Three biostratigraphic zones, Palaeofusulina-Colaniella Zone, Hindeodus parvus Zone, and Isarcicella staeschei Zone, are identified. The excursion of δ¹³C_carb exhibits a sharp negative shift in the calcimicrobialite at the P/Tr boundary, which is roughly accordant with the abrupt bioclastic decline. In addition, five types of microfacies are recognized, including algal-foraminifer bioclastic limestone, algal-laminated calcimicrobial limestone, oolitic grainstone, vermiculate limestone, and intraclastic wackstone. The results indicate that the changeover of ecosystem from metazoan reef to calcimicrobialite in Cili is a classic case of marine ecological evolution during the Paleozoic-Mesozoic transition. Supported by National Natural Science Foundation of China (Grant Nos. 40830212, 40621002, 40730209) and National Basic Research Program of China (Grant No. 2006CB80640)