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991.
Objectives for Multiple-Species Conservation Planning 总被引:2,自引:0,他引:2
Abstract: The first step in conservation planning is to identify objectives. Most stated objectives for conservation, such as to maximize biodiversity outcomes, are too vague to be useful within a decision-making framework. One way to clarify the issue is to define objectives in terms of the risk of extinction for multiple species. Although the assessment of extinction risk for single species is common, few researchers have formulated an objective function that combines the extinction risks of multiple species. We sought to translate the broad goal of maximizing the viability of species into explicit objectives for use in a decision-theoretic approach to conservation planning. We formulated several objective functions based on extinction risk across many species and illustrated the differences between these objectives with simple examples. Each objective function was the mathematical representation of an approach to conservation and emphasized different levels of threat. Our objectives included minimizing the joint probability of one or more extinctions, minimizing the expected number of extinctions, and minimizing the increase in risk of extinction from the best-case scenario. With objective functions based on joint probabilities of extinction across species, any correlations in extinction probabilities had to be known or the resultant decisions were potentially misleading. Additive objectives, such as the expected number of extinctions, did not produce the same anomalies. We demonstrated that the choice of objective function is central to the decision-making process because alternative objective functions can lead to a different ranking of management options. Therefore, decision makers need to think carefully in selecting and defining their conservation goals. 相似文献
992.
Habitat Suitability Models and the Shortfall in Conservation Planning for African Vertebrates 总被引:4,自引:0,他引:4
Abstract: Ongoing loss of biodiversity requires identifying large-scale conservation priorities, but the detailed information on the distribution of species required for this purpose is often missing. We present a systematic reserve selection for 1223 African mammals and amphibians in which habitat suitability models are used as estimates of the area occupied by species. In the framework of the World Conservation Union (IUCN) Global Amphibian Assessment and IUCN Global Mammal Assessment, we collected the geographic range (extent of occurrence) and habitat preferences for each species. We used the latter to build species-specific habitat suitability models inside geographic ranges, and for 181 species we verified the models by comparing suitability levels to presence-absence data collected in the field. We then used the suitable areas as estimators of the area of occupancy and compared the results of systematic reserve selection based on geographic ranges to those based on estimated areas of occupancy. Our results showed that the reserve system would need a 30-100% expansion to achieve minimal conservation targets, concentrated in the tropics, where species richness reaches a maximum. Comparative analyses revealed that using geographic ranges, which overestimate the area occupied by species, underestimates the total amount of area that needs to be conserved. The area selected for conservation doubled when we used the estimated area of occupancy in place of the geographic ranges. This happened because the suitable areas potentially occupied by each species overlapped less than their geographic ranges. As a result, any given protected area contained fewer species than predicted by the analysis of ranges. Because species are more specialized than our estimates of distribution based on extent of occurrence suggest, we propose that this is a general effect in systematic conservation planning. 相似文献
993.
改性天然沸石去除水中氨氮的研究 总被引:22,自引:0,他引:22
分别采用NaCl、KCl和CaCl2对黑龙江省某市天然沸石进行改性,考察了pH值、氨氮初始浓度以及温度对改性沸石交换性能的影响,并对改性沸石的交换动力学进行了研究。结果表明,NaCl和KCl改性对沸石原矿交换容量有不同程度提高,而KCl改性后容量有所降低。pH、NH4初始浓度以及温度对交换性能有明显影响,pH6.0附近沸石交换容量最大;NH4初始浓度越高,反应速度越快,相同初始浓度下,钾型沸石交换速度较快,而沸石原矿交换速度最慢。采用Langmuir型离子交换等温线进行非线性回归的结果显示,低温有利于交换反应的进行。溶液中NH4^+在改性沸石上的离子交换反应可采用Vermeulen模型描述,沸石原矿拟合相关系数较差。改性沸石多次再生后,其交换容量均有所降低。 相似文献
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995.
文章根据石油天然气勘探开发的实际情况,对石油天然气生产、储存、集输过程中的污染防治和生态环境保护进行了深入的研究,提出了相应的法律措施和手段. 相似文献
996.
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998.
我国农业自然资源法的问题与改善途径初探 总被引:6,自引:0,他引:6
在介绍我国农业自然资源基本法律体系的基础上,分析了现行法律存在的主要问题,提出了强化农业资源管理的若干建议:①制定农业自然资源综合法律,完善农业自然资源法律体系;②更新充实现行农业自然资源法,以适应社会主义市场经济的要求;③从机制和手段两方面革新管理体制,强化农业自然资源相对统一的综合管理。 相似文献
999.
区域农业可持续发展的生态安全及其评价研究 总被引:91,自引:3,他引:91
资源、生态环境是区域农业可持续发展的核心和基础。农业可持续发展的生态安全是指农业赖以发展的自然资源、生态环境处于一种不受威胁、没有危险的健康、平衡的状态 ,具有战略性、整体性、区域性、层次性和阶段性等特点。文章以浙江省嘉兴市为例 ,讨论了区域农业可持续发展的生态安全评价的基本过程和方法 ,提出了包括资源生态环境压力、质量和保护整治能力三方面23项指标在内的生态安全评价的指标体系 ,以及不安全指标阈值的确定和不安全指数的计算方法 ,提出了区域农业可持续发展的生态安全建设的途径和对策。 相似文献
1000.
长白山自然保护区生物多样性旅游价值评估研究 总被引:73,自引:4,他引:73
在野外调查的基础上,采用费用支出法、旅行费用法(TCM)及条件价值法(CVM)对长白山自然保护区生物多样性旅游价值进行了评估。旅游价值估算为游客的旅行费用支出、消费者剩余、时间价值和其他花费之和。计算消费者剩余使用了国外流行的TCM技术,通过全国地理小区划分和3131位游客的现场抽样调查,计算出游客出发小区的旅游率,建立了旅游率与人口、收入、旅行费用及旅行时间等因变量之间的回归模型和“供给-需求曲线”,求出全体游客的消费者剩余。计算结果表明,1996年长白山保护区生物多样性旅游价值为43205万元,其中国内旅游价值13783万元,国外旅游价值29422万元。 相似文献