Using economic incentives and regulations to reduce seawater intrusion in the Batinah coastal area of Oman

Excessive groundwater abstraction is a major problem in Oman, primarily in the Batinah coastal area where it results in seawater intrusion. The Government began to address the problem in the 1990s by encouraging the use of more efficient irrigation systems, replacing date palms with winter vegetable crops and using treated wastewater for municipal irrigation. However, 15 years later, seawater intrusion in the Batinah aquifers is still advancing at an alarming pace. This paper analyses the relative merits of strategies to control groundwater pumping based on water quotas, electricity quotas and electricity pricing. A cost benefit approach is used to evaluate the feasibility of three strategies over a period of 25 years and to compare them to the “business as usual” option. Results show that the net present loss to the community when no active policy is implemented amounts to (−$288) million. Imposing water quotas on tubewells would give a net present benefit of $153 million. However, such quotas would give the lowest present benefit and create inequity among farmers. Other possible approaches would be to control the pumping of groundwater from all wells - tubewells and dug wells - by enforcing energy quotas and by increasing the price of electricity used to pump water. The net present benefits would be greater and the costs to farmers would be more fairly spread. The results of cost-benefit analysis show that enforcing an electricity quota, coupled with removal of the subsidy on the electricity price, is the easiest and most equitable solution to implement.     

关税配额的经济理论与政策分析

基于局部均衡分析，从理论上关税配额政策的经济效应进行了讨论，并与关税、配额等进口限制措施进行了比较，认为虽然关税配额同时具有关税和配额的特点，但从根本上说它有关税的特征，对于WTO的农产品贸易谈判，关税配额是一个过渡性保护措施，进一步的贸易自由谈判将会从增加关税配额的配额的数量、降低配额外关税水平两方面对该措施进行约束，文中对我国的农产品保护和关税调整提出了建议。     

How do individual transferable quotas affect marine ecosystems?

Published papers were reviewed to assess ecosystem impacts of individual transferable quotas (ITQs) and other dedicated access systems. Under ITQs, quota shares increase with higher abundance levels, thus fishers may request lower total allowable catches (TACs) and pay for monitoring and research that improves fishery sustainability. Mortality on target species generally declines because catches are closer to TACs and because ghost fishing through lost and abandoned gear decreases. High-grading and discarding often decline, but may increase if landings (and not catches) count against ITQs and when there is little at-sea enforcement. Overall, ITQs positively impact target species, although collapses can occur if TACs are set too high or if catches are routinely allowed to exceed TACs. Fishing pressure may increase on non-ITQ species because of spillover from ITQ fisheries, and in cases where fishers anticipate that future ITQ allocations will be based on catch history and therefore increase their current catches. Ecosystem and habitat impacts of ITQs were only sparsely covered in the literature and were difficult to assess: ITQs often lead to changes in total fishing effort (both positive and negative), spatial shifts in effort, and fishing gear modifications. Stock assessments may be complicated by changes in the relationship between catch per unit effort, and abundance, but ITQ participants will often assist in improving data collection and stock assessments. Overall, ITQs have largely positive effects on target species, but mixed or unknown effects on non-target fisheries and the overall ecosystem. Favourable outcomes were linked to sustainable TACs and effective enforcement.     

加入WTO对吉林农业的影响及对策研究

系统地分析了中国加入WTO对吉林省农业发展的利弊 ,提出了吉林农业发展的战略思路、对策及政策建议。     

2030年中国主要省域间碳排放配额测算

[目的]在控制碳排放总量条件下,对省域间碳排放配额进行公平科学地分配是实现“双碳”目标的关键途径,也是碳排放交易机制体系的重要基石。分析不同情景下碳排放配额测算结果的碳减排边际成本,以期以最小成本确定最优的碳排放定额分配方案,为区域后期开展分配工作提供理论基础,为地区碳减排方案制定提供工作参考。[方法]在前人建立的碳配额测算指标基础上引入生态性指标,并设置公平、效率、生态、兼顾公平—生态—效率4种情景,利用SBM(slacks-based measure)对偶模型测算不同情景下区域碳边际减排成本,并以此为依据确定最优分配方案。[结果]在公平、效率、生态、兼顾情景下平均碳边际减排成本分别为2 950,3 120,2 910,3 090元/t,引入生态性指标的方案减排成本明显更低,可推断出是碳汇抵消掉部分减排难度较大,成本较高的碳排放所致;兼顾情景下减排成本明显高于公平、生态情景,表明碳排放效率的提升同时会导致碳边际减排成本增加。[结论]生态情景下的碳排放配额是以最低碳边际减排成本实现“双碳”目标的最优方案,在地区碳排放方案及碳交易机制制定时应予以重视。     

国营林场抚育间伐伐区工艺设计诸问题研探

本文对抚育间伐伐区工艺设计中的采伐类型、伐区等级、间伐强度、作业定额、设计表的研究提出探讨意见。     

Thirty years later: the global growth of ITQs and their influence on stock status in marine fisheries

Individual transferable quota (ITQ) programmes have been incorporated into many marine fisheries management strategies for 30 years, but their implementation and utility remains controversial. This study provides an overview of the global status of ITQ programmes, the reasons they have been adopted and the changes in stock biomass after their implementation. Eighteen countries currently use ITQs to manage several hundred stocks of at least 249 species. ITQs were adopted in these countries for many reasons: overcapitalization, economic gains, safety concerns for fishers and political change. The implementation of ITQs does not translate into consistent changes in stock biomass. Improvements in 12 of 20 stocks after ITQs were introduced suggest that ITQs can be an effective component of fisheries management strategies, but eight of the stocks continued to decline after ITQs were introduced. This suggests that alternative or complementary measures are needed to sustain those fisheries, such as combining ITQs with more effective total allowable catches, better enforcement and monitoring, and implementing aspects of ecosystem-based fisheries management.     

Can small-scale fisheries survive market-based management? Nordic evidence

Market-based fisheries management systems give incentives to reduce the fleet size and employment, which increases earnings and contributes to resolve the tragedy of the commons. However, the often-stated expectation that economies of scale cause the disappearance of small-scale fishery is not observed in many cases. In this study, we investigate the effects on fleet structure in the period after introducing individual fishing quotas or individual fishing days with various degrees of transferability in selected fisheries in the seven Nordic countries. Despite observing economies of scale in most cases, it is found that the market-based fisheries management often does not reduce the small-scale fleet more than the fleet of large vessels. This is explained partly by small vessels targeting demersal species and large vessels pelagic species, and partly by the larger need of larger than small vessels to continuously utilize their capital stocks through fast adaptation to ensure return. A more important explanation is the regulation design, with limitations in sale of fishing rights and lease between vessel groups and regions and in the share of the total quota holdings of fishing rights by individuals and vessels. This is important for countries considering the introduction of market-based fisheries management, since the Nordic experiences show that with proper regulation design, economic gains can be achieved with small-scale fishing surviving even under economies of scale.     

泌乳量对荷斯坦泌乳牛某些血尿生化指标的影响

随机选取正常泌乳牛36头，按泌乳量分成3组，每组12头。对各组的血酮、尿酮、血糖、Ca、p、Mg、ALP、GPT、GOT、BUN等指标进行检测。结果表明：3组泌乳牛之间，尿酮差异极显著（P＜0.01），血酮、血糖差异显著（P＜0.05）。随产奶量的增加，血酮、尿糖升高，血糖降低。但三组血清Ca、P、Mg、ALP、GPT、GOT、BUN等指标均无显著差异（P＞0.05）。     

灌水处理对漫灌改滴灌红枣土壤盐分时空分布的影响

为确定南疆沙区成龄红枣漫灌改滴灌适宜的滴灌模式,采用双因素组合试验设计,研究了不同灌溉定额(900,1 050,1 200mm)和灌水次数(10,14,18次)对红枣漫灌改滴灌后整个生育期0—200cm土层盐分时空分布及产量的影响。结果表明:水平方向上各处理均表现为距树干越远土壤盐分质量比越高,增大灌溉定额使距树干60cm处0—20cm土层土壤盐分质量比明显增大;增加灌水次数可以显著降低距树干60cm处0—80cm土层土壤盐分质量比。垂直方向上土壤盐分质量比呈"S"形分布,表层土壤有明显积盐现象;不同灌溉定额处理垂直方向上均出现一个低盐带(2g/kg),低盐带深度范围随灌溉定额的增加而增大。漫灌相比改滴灌水平方向上土壤盐分质量比变化不大,且表层土壤也无明显积盐现象。整个生育期内,各处理土壤盐分质量比峰值出现在6月新稍期或7月花期;在0—200cm土层,10次、1 200mm灌水处理和14次、900mm灌水处理的盐分淋洗效果与漫灌CK处理相近,漫灌处理只在0—100cm土层盐分淋洗效果明显优于改滴灌处理。灌水次数对0—200cm土层各时间阶段土壤盐分质量比的影响弱于灌溉定额。漫灌改滴灌不同于连续滴灌,漫灌改滴灌后,过低或过高的灌溉定额均不利于提高红枣的产量,与其他处理相比,18次、1 050mm灌溉定额处理不但具有合理的盐分时空分布,且产量(7 549kg/hm2)和水分利用效率最高,比漫灌增产12.87%,节水30%,可以作为当地节水、高产和高效的红枣漫灌改滴灌灌溉制度。