Water Resource Management in Botswana: Balancing Sustainability and Economic Development*

Botswana is a rapidly developing country in southern Africa. Over the last three decades, diamond mining and tourism have provided double-digit rates of economic growth. Yet most of Botswana’s land is in the Kalahari desert where the climate is subject to sustained periods of severe drought. In this environment, water resources are the most crucial of all environmental resources. Water use directly affects economic development because water utilization impacts all the major national economic sectors. A sustainable water use resource management plan must stretch several decades into the future to assure the availability of adequate supplies of water to future generations while not compromising the ability of the current generation to reasonable rates of economic development. Yet thinking about sustainability is present in Botswana water policy mostly only in rhetoric. A series of cultural traditions and political constraints, coupled with bureaucratic managerial weaknesses, serve to maintain a system of water allocation that is unsustainable in the long run and inefficient in the short-term. Unless sustainable water use patterns are adopted, the results for the short-term, as well as the long-term, will be devastating. Drawing on data obtained through a series of interviews with government officials, leaders of non-governmental organizations (NGOs), and water resource researchers, this paper explores water policy in Botswana within the larger context of sustainable natural resource management practice and the pressures of economic development. This research was partially funded under U.S. Department of State, College and University Affiliations Grant # ASCS-1095.     

企业采用自愿协议式环境管理方法的意愿调查

“企业采用自愿协议式环境管理方法的意愿调查”是欧盟资助项目“自愿协议式环境管理方法在中国工业环境管理中应用的可行性研究”的主要成果之一。调查结果表明，自愿协议式环境管理方法目前在中国只是处于初步的认知阶段，但大多数企业愿意尝试采用自愿协议式方法解决环境问题，积极性较高，且谈判式自愿协议被看好。     

Stand density index applied to timber and goshawk habitat objectives in Douglas-fir

Silvicultural guidelines are presented for the management of intermountain Douglas-fir (Pseudotsuga menziesii) stands for sawtimber production and goshawk (Accipiter gentilis) nesting habitat in the northern Rocky Mountains. Data from 14 goshawk nest stands in Douglas-fir forests on the Targhee National Forest in Idaho (Patla 1991) were used to characterize the range of stand conditions considered suitable for goshawk nesting. A density management regime is presented using Reineke's stand density index that includes a technical rotation designed to produce sawlogs with a single commercial thinning. On average timber-growing sites, stands reach goshawk habitat suitability when site height is 25 m at age 75 and provide 65 years of goshawk nesting habitat until the final harvest at age 140. Approximately 1320 m³/ha are harvested over the rotation. On higher-quality sites, rotation length declines from 140 to 85 years, of which roughly 35 years are suitable for goshawk nesting.     

Evaluating the acceptability of recreation rationing policies used on rivers

Research shows that users and managers have different perceptions of acceptable policies that ration or limit recreational use on rivers. The acceptability of seven rationing policies was evaluated using Thurstone's method of paired comparisons, which provided a rank ordering of advance reservation, lottery, first-come/first-served, merit, priority for first time users, zoning, and price. Chi-squared tests were used to determine if users and managers have significantly different levels of acceptability for the policies. River users and managers were found to be significantly different according to their evaluation of advance reservation, zoning, and merit. The results also indicated that river users collectively divide the policies into three categories corresponding to high, moderate, and low levels of acceptability, while river managers divide the policies into two levels corresponding to acceptable and unacceptable.     

Effect of land management on soil microbial N supply to crop N uptake in a dry tropical cropland in Tanzania

In Sub-Saharan Africa, conservation of available soil N during early crop growth, when N loss by leaching generally occurs, is important to improve crop productivity. In a dry tropical cropland in Tanzania, we assessed the potential role of soil microbes as a temporal N sink-source to conserve the available soil N until later crop growth, which generally requires substantial crop N uptake. We evaluated the effect of land management [i.e., no input, plant residue application before planting (P plot) with or without fertilizer application, fertilizer application alone, and non-cultivated plots] on the relationship between soil N pool [microbial biomass N (MBN) and inorganic N] and crop N uptake throughout the ∼120-d crop growth period in two consecutive years. In the P plot, MBN clearly increased (∼14.6-29.6 kg N ha⁻¹) early in the crop growth period in both years because of immobilization of potentially leachable N, and it conserved a larger soil N pool (∼10.5-21.2 kg N ha⁻¹) than in the control plot. Especially in one year in which N leaching was critical, increased MBN maintained a larger soil N pool in the P plot throughout the experimental period, and a delay of increased MB C:N ratio and a substantial decrease in MBN was observed, indicating better soil microbial N supply for crop N uptake during later crop growth. Therefore, plant residue application before planting should enhance the role of soil microbes as a temporal N sink-source, leading to the conservation of potentially leachable N until later phase of crop growth, especially in years in which N leaching is relatively severe. Although further studies are necessary, our results suggest that plant residue application before planting is a promising option to achieve better N synchronization.     

Responses of plant, insect and spider biodiversity to local and landscape scale management intensity in cereal crops and grasslands

The aim of this study was to determine the relative effects of landscape scale management intensity, agroecosystem type, local management intensity and edges on diversity patterns of functional groups of plants, carabid beetles, spiders and grasshoppers. Nine landscapes were selected differing in percent intensively used agricultural area (IAA), each with a pair of organic and conventional winter wheat fields and a pair of organic and conventional mown meadows. Within fields, plants were surveyed in the edge and in the interior. Carabid beetles and spiders were captured by funnel traps, while grasshoppers were sweep-netted in the meadows. Diversity patterns of study organisms were affected both by local variables (local management, agroecosystem type and within-field position) and by landscape scale management intensity. Species richness of grasses, presumably because of sowing low-diversity mixtures, and hunting spiders decreased with percent cover of IAA. Meadows differed from wheat fields in that they had higher species richness of forbs and grasses, as well as higher densities of hunting spiders. In contrast, more carabid individuals, especially of non-carnivore species, were captured in wheat fields. In field edges with their reduced management intensity and increased immigration, species richness of plants, carabids and spiders was higher than in the interiors regardless of agroecosystem type and management. Organic management enhanced forb richness and cover in both agroecosystem types. Organic management also increased grass cover in wheat fields, but not in meadows, and promoted species richness of non-carnivore carabids and hunting spiders, but not grasshoppers. The results show that agri-environmental management needs to be targeted to the agroecosystem's field size, because higher edge area led to higher species richness. Organic management affected several functional groups positively (forbs, non-carnivore carabids, hunting spiders), while lower landscape scale management intensity only increased species richness of grasses and spiders. The great differences in responses of functional groups to local cereal and grassland as well as landscape management suggest implementing more scale and group specific targets for agri-environmental schemes to improve their efficiency.     

耕地资源非市场价值评价方法的研究进展与述评

论文系统梳理了国内外耕地资源非市场价值评价方法的研究进展,指明了今后该领域研究的努力方向。研究结果表明:国内评价耕地资源非市场价值的方法主要是CVM,研究方法单一,缺少同时运用其他非市场价值评价方法来对CVM的研究进行比较的案例,从而无法清晰辨识CVM的缺陷,并对其加以改进;而且,CVM方法本身存在一些不足,大多数CVM的应用尚停留在实施CVM实验并报告结果的初级阶段,对CVM的有效性与可靠性方面的相关研究不够。国外非市场价值评价方法表现出两个特点:一是研究方法不断拓展,Mixed Logit逐步得到应用;二是研究方法不断深化,对CVM的研究从调研内容与结果的报告,向检验结果的有效性、可靠性方向转变,进而转向CVM的经济学理论的探讨和研究;对CVM与预期不相符合的原因进行深入研究;对问卷的设计进行深入研究;并将非市场价值评价模型和方法与空间分析相结合。在此基础上,建议将CE模型引入中国的耕地资源非市场价值评价研究;加强耕地资源非市场价值的空间分异特征与分异规律,以及耕地资源非市场价值形成的空间分异机理和动态演变规律的研究;尝试调查问卷设计中的可视化研究。     

基于ESDA的京津冀地区草地变化空间分异

论文以县域为基本研究空间单元,借助GIS软件与Geoda空间统计分析软件,利用ESDA方法,对京津冀地区县域草地资源数量变化的总体与局域空间差异进行了分析。结果表明:①1980-2000年京津冀地区草地动态变化系数的Global Moran’s I为0.184 4,α = 0.05时呈显著的空间正相关,草地变化呈现出较明显的空间集聚特征;②时段Ⅰ(1980-1995年)到时段Ⅱ(1995-2000年)的全局Moran指数有所增加,表明草地变化在空间分布上集聚的趋势在增强;③各县域Local Moran’s I的Grid图反映了京津冀地区草地变化在局域空间上的均质性,尤其是高值区域与低值区域的集聚特征十分显著;④LISA集聚4种类型中,正相关的"H-H"类型区、"L-L"类型区占主体部分,二者约占总数的70%以上,其中,在时段Ⅱ,"H-H"关联的县域主要聚集在西北部山区,而中部的平原区域则表现出明显的"L-L"关联特征。     

施用餐厨垃圾调理剂对果园土壤有机碳组分的影响

为研究施用餐厨垃圾调理剂对土壤有机碳组分的影响,以果园土壤为研究对象,从时间、空间维度解析长期施用餐厨垃圾调理剂对土壤有机碳积累、组成及其分布规律的影响,结合CPMI（碳库管理指数）和相关性分析,揭示施用餐厨垃圾调理剂对土壤碳汇的影响机制.结果表明,施用餐厨垃圾调理剂可显著提高土壤中w（TOC）（TOC为总有机碳）,并随施用时间的增加逐渐向深层土壤迁移,改善TOC分布状况.随着施用餐厨垃圾调理剂时间的增加,0~20 cm土壤层中w（NOC）（NOC为非活性有机碳）和30~40 cm土壤层中w（AOC）（AOC为活性有机碳）呈增加趋势,AOC分配比例低于NOC分配比例.随着施用时间的增长,0~30 cm土壤层中w（POC）（POC为颗粒有机碳）显著提高,最大值为42.94 mg/g,MOC（矿质结合态有机碳）分配比例与POC分配比例呈相反变化趋势,有利于提高土壤碳稳定性.各土壤层中CPMI均大于空白对照组,最大值为154.437,表明施用餐厨垃圾调理剂有利于提升土壤肥力.相关性分析表明,w（POC）与pH呈负相关,与含水率、EC（电导率）、w（OM）（OM为有机质）呈正相关,其中与含水率相关性最高（R=0.91）.可见,长期施用餐厨垃圾调理剂对提高果园土壤碳汇、改善土壤肥力具有重要意义,研究结果有助于进一步提升土壤碳汇的新型土壤调理剂的研发与应用.      

从生物群落到生态系统综合保护：国家公园生态系统完整性保护的理论演变

自然保护事业已经进入人与自然和谐的综合保护阶段,突破传统生物群落保护的要素式思维,从生态特征、生态系统健康和自组织能力等视角系统实施生态系统完整性保护,已基本成为共识。中国经历了长期部门化割裂管理,在国家公园体制建设过程中开始由分散走向统一,要求将山水林田湖草作为生命共同体进行生态系统完整性保护。基于集合种群等空间生态学理论,提出国家公园生态系统完整性不仅意味着内部自然空间的完整,更需着眼国家生态安全的大局和自然保护地体系的战略布局。国家公园只有成为生态地理区的节点并辐射周边区域,有效平衡行政区域之间以及人与自然之间的关系,才能真正实现完整生态系统的长效保护。目前,国内既有研究在指导全域布局和平衡人地关系方面仍考虑不足,试点过程中还存在管理型技术方法欠缺、空间边界受限于行政边界、未能从全局着眼构建以国家公园为核心的生态系统完整性网络、未充分考虑差异化的人地关系等问题。未来需要着眼大局,有效平衡国家公园及其周边区域的关系、不同行政区域之间的关系、国家公园人与自然的关系,从而实现生态系统完整性的长效保护。