The economic benefits and costs of trees in urban forest stewardship: A systematic review

Understanding the benefits provided by urban trees is important to justify investment and improve stewardship. Many studies have attempted to quantify the benefits of trees in monetary terms, though fewer have quantified the associated costs of planting and maintaining them. This systematic review examines the methods used to jointly analyse the costs and benefits of trees in the urban landscape, assesses the relative balance of benefits and costs, and attempts to understand the wide variation in economic values assigned in different studies. The benefits most frequently studied are those related to environmental regulation and property values, and the available data show that these usually outweigh the costs. Aesthetic, amenity, and shading benefits have also been shown to provide significant economic benefits, while benefits in terms of water regulation, carbon reduction and air quality are usually more modest. Variation in benefits and costs among studies is attributed largely to differences in the species composition and age structure of urban tree populations, though methodological differences also play a role. Comparison between studies is made difficult owing to differences in spatiotemporal scope, and in the way urban forest composition and demographic structure were reported. The overwhelming majority of studies concern deciduous trees in Northern America, and much less is known about urban forests in other regions, especially in the tropics. Future work should thus seek to fill these knowledge gaps, and standardise research protocols across cities. In light of ambitious goals in many cities to increase tree cover, ongoing advances in valuation methods need to provide a more comprehensive accounting of benefits and costs, and to better integrate economic assessment into the decision-making process.     

Benefits of prophylactic gastropexy for dogs at risk of gastric dilatation-volvulus

The lifetime probability of death from gastric dilation–volvulus (GDV) for five dog breeds was estimated based on published breed-specific longevity and GDV incidence. These breeds were Great Dane, Irish Setter, Rottweiler, Standard Poodle and Weimaraner. Lifetime risk (95% CI) of GDV in these breeds ranged from 3.9% (0–11.2%) for Rottweiler to 36.7% (25.2–44.6%) for Great Dane.

A decision-tree analysis for prophylactic gastropexy—using lifetime probability of death from GDV and expected cost savings for veterinary services as outcome measures—was undertaken to determine the preferred course of action in several dog breeds. Prophylactic gastropexy was the preferred choice of action for all breeds examined, with the reduction in mortality (versus no gastropexy) ranging from 2.2-fold (Rottweiler) to 29.6-fold (Great Dane). Assuming a prophylactic gastropexy costs US$ 400, the procedure was cost-effective when the lifetime risk of GDV was ≥34%. The maximum and minimum estimated breakeven costs for the gastopexy procedure ranged from US$ 20 (Rottweiler) to US$ 435 (Great Dane). The cost-effectiveness of prophylactic gastropexy was most sensitive to the cost of treating GDV (US$ 1500). Prophylactic gastropexy raises ethical issues that need to be considered by veterinarians and dog breeders.     

Comparison of image and rapid field assessments of riparian zone condition in Australian tropical savannas

Suitable methods for measuring and monitoring the condition of riparian environments are being investigated by government agencies responsible for maintaining these environments in Australia. The objective of this work was to compare two riparian condition assessment approaches, the Tropical Rapid Appraisal of Riparian Condition (TRARC) method developed for rapid on-ground assessment of the environmental condition of savanna riparian zones and an image based riparian condition monitoring scheme. Measurements derived from these two approaches were compared and correlated. The sample representativeness of the TRARC method was evaluated and the cost-effectiveness and suitability for multi-temporal analysis of the two approaches were assessed. Two high spatial resolution multi-spectral QuickBird satellite images captured in 2004 and 2005 and coincident field data covering sections of the Daly River in the Northern Territory, Australia were used in this work. Both field and image data were processed to map indicators of riparian zone condition including percentage canopy cover, organic litter on the ground, canopy continuity, tree clearing, bank stability, and flood damage. Spectral vegetation indices, image segmentation, and supervised classification were used to produce riparian health indicator maps. QuickBird image data were used to examine if the spatial distribution of TRARC transects provided a representative sample of ground based estimates of riparian health indicators. Covering approximately 3% of the study area, the sample mean of the TRARC estimates of individual indicators of riparian zone condition were in most cases within 20% of the global mean derived from the whole imaged riparian area. The cost-effectiveness of the image based approach was compared to that of the ground based TRARC method. Results showed that the TRARC method was more cost-effective at spatial scales from 1 km to 200 km of river in relatively homogeneous riparian zones along rivers with only one channel, while image based assessment becomes more feasible at regional scales (200–2000 km of river). A change detection analysis demonstrated that image data can provide detailed information on gradual change, while the TRARC method is less suited for multi-temporal analysis due to the ranked data format, which inhibits precise detection of change. However, results from both methods were considered to complement each other for single date assessment of riparian zones if used at appropriate spatial scales.     

Contrasting the spatial management of nitrogen and phosphorus for improved water quality: Modelling studies in New Zealand and France

Critical source areas (CSAs) define areas of a farm or catchment that emit the majority of water quality contaminants but account for a minority of the area at a field, farm or catchment scale. Using process based modelling we tested the hypothesis that the definition and management of CSAs would decrease losses of phosphorus (P) in two New Zealand catchments and nitrogen (N) in a French catchment. In the New Zealand catchment, CSAs of P loss were isolated to small areas within fields commensurate with surface flow pathways, while in the French catchment, CSAs for N loss were influenced by factors (inputs and land use) relevant at a field (or multiple field) scale. Scenarios were tested that examined the management of CSAs versus whole field management for P, and decreasing N loss within CSAs by increasing the proportion of grassland fields and changing their location relative to cropland. The results showed that N losses decreased by up to 25% as more grassland was incorporated into the catchment, especially in wet areas near valley bottoms due to a longer growth period and better utilisation/storage of N than cropland. For P, focusing mitigation on CSAs decreased catchment losses to a similar degree as mitigations applied across the whole catchment, but was on average 6–7 times more cost-effective. Therefore, the definition and management of CSAs at an appropriate scale is recommended to improve water quality and minimise the impact on farm profitability.     

新时期农业科技推广体系的创新与构建

随着我国农村经济和社会的发展,农业科技推广的定义、本质、目的、目标及任务应当重新界定.我国现行农业科技推广体系存在着农业科技推广工作效率较低,推广人员热情不高等主要问题.构建科学、适用的当代中国农业科技推广体系的主体构架,即建立农业科技推广体系的程序构架,最关键的是要建立农业科技推广应当遵循的原则,创新现有的农业科技推广模式,并做好效益评估.     

山西优质杂粮开发成本效益对策研究

对山西杂粮的加工、流通、绿色认证等情况进行了全面的调查,结果显示：山西省小杂粮商品量占总产量的10%,加工量仅为2%;小杂粮加工企业基本上是种类齐全、加工产品多样的中、小型企业,以销定产,营销手段灵活,带有粮油综合加工性质;山西省的一大批杂粮获奖产品,甚至很多的高档次获奖产品,并没有得到规模开发,也没有对基地发展发挥强大的带动作用。在此基础上,找出了山西目前优质杂粮产业存在的优势,提出了山西优质杂粮产业发展的对策。     

不同的施肥用药组合对黄瓜产量及成本效益影响的研究

为了黄瓜种植时合理的施用肥料和农药提供参考,缓解当前严重的环境污染和蔬菜农药残留超标问题,探讨不同的施肥用药情况对黄瓜产量以及成本投入的影响。以黄瓜为试材,设置4个不同的处理,分别为T1(习惯施肥+习惯用药,CK)、T2(习惯施肥+推荐用药)、T3(推荐施肥+习惯用药)、T4(推荐施肥+推荐用药)。结果表明:T4处理在肥料和药剂的种类数量上比对照处理少得多,并且对黄瓜的产量还起到了增产的作用,在黄瓜全采收期增产了7003.5 kg/hm~2,增产率达到了19.25%;在节本增效上效果也显著,跟对照相比,T4处理节本达到10941元/hm~2,增效达到31951.5元/hm~2。该试验获得了理想的结果,以较低的投入得到了较高的收益,可以为黄瓜种植者在肥料选择和喷施农药时提供参考,为缓解现在日趋严重的农田土壤生态环境奠定基础。     

Economic evaluation of Johne's disease control programs implemented on six Michigan dairy farms

Johne's disease (JD) is an incurable, chronic infectious disease prevalent in dairy herds throughout the US and the world. The substantial economic losses caused by JD have been well documented. However, information on the costs of controlling the disease is limited, yet necessary, if producers are to make sound decisions regarding JD management. The purpose of this paper is to describe a method for evaluating the cost-effectiveness of management changes to control JD on infected dairy farms. A 5-year longitudinal study of six dairy herds infected with JD was performed. Each herd implemented a JD control program upon study enrollment. Prevalence of JD within each herd was monitored with annual testing of all adult cows using fecal culture and/or serum ELISA. Individual cow production and culling information was collected to estimate the annual economic losses caused by JD. An economic questionnaire was developed and administered to each herd annually to estimate costs directly attributable to the JD control program. Based on the costs of the control program, and using the losses to estimate the potential benefits of the control program, the net present value (NPV) of the control program was calculated for each herd during the study and projected into the future for a total of 20 years. The NPV was calculated for four different scenarios: (1) assuming a linear decline in losses beyond the observed period of the study with JD eradication by year 20 of the control program; (2) assuming losses and JD prevalence remain constant at the rate equal to that of the last observed year while continuing the control program; (3) assuming linear increase in losses at rate equal to that in scenario 1 with no control program; and (4) assuming losses remain constant at same level as the beginning of the study with no control plan implemented. The NPV varied greatly across the herds. For scenario 1, only three herds had a positive NPV; and only two herds had a positive NPV under scenario two. In the absence of a control program, the NPV's were always negative. The costs of the JD control programs implemented on these herds averaged $30/cow/year with a median of $24/cow/year. The annual losses due to JD averaged $79/cow/year with a median of $66/cow/year. Investing in a JD control program can be cost-effective.     

Evaluation of testing strategies for infectious salmon anaemia and implications for surveillance and control programs

Infectious salmon anaemia (ISA) is an economically important disease in New Brunswick, Canada. Current regulatory control involves detection of ISAv in broodstock, hatcheries and marine sites through a surveillance program. Prior to recent assessments of operating characteristics of diagnostic tests, the efficiency of this surveillance program was difficult to evaluate. In order to determine the optimal testing strategies for various phases of production, a cost-effectiveness analysis was done for different strategies including single testing and multiple testing with results interpreted in series or in parallel. The lowest cost testing strategy, which would achieve a group-level sensitivity (GSe) of 95% and a group-level specificity (GSp) of 95%, was determined for each production phase. Our analyses showed that the most cost-effective testing strategy depended on the production phase. If sampling is to be carried out in a freshwater facility, then broodstock should be tested by VI alone, while pre-smolts should be tested with IFAT and VI used in series. For fish reared in saltwater, parallel interpretation of results from VI and RT-PCR, or testing with VI alone, are appropriate testing strategies for broodstock. For market-fish, PCR alone is a good screening option. If one assumes the prevalence of ISAv in moribund fish is at least 50%, then a maximum of 5 fish (at a cut-point of 1 positive fish to designate a cage as positive) need to be tested at a cost of $220. If one desired to have a perfect GSp (i.e. no false positive cage designations), serial testing with IFAT and VI is a better option. However, for this strategy a maximum of 9 fish (at a cut-point of 1) need to be tested at a cost of $472.     

山西优质杂粮开发成本效益对策研究

对山西杂粮的加工、流通、绿色认证等情况进行了全面的调查,结果显示:山西省小杂粮商品量占总产量的10%,加工量仅为2%;小杂粮加工企业基本上是种类齐全、加工产品多样的中、小型企业,以销定产,营销手段灵活,带有粮油综合加工性质;山西省的一大批杂粮获奖产品,甚至很多的高档次获奖产品,并没有得到规模开发,也没有对基地发展发挥强大的带动作用。在此基础上,找出了山西目前优质杂粮产业存在的优势,提出了山西优质杂粮产业发展的对策。