An economic analysis of farm forestry as a means of controlling dryland salinity

Large areas of agricultural land under conventional crops and pastures are at risk of dryland salinisation in Australia. The salinisation problem can be controlled by strategic and large-scale planting of trees; however, farm forestry enterprises evaluated with conventional discounting techniques do not generally rank as an attractive alternative to annual crops on productive land. In this article, an optimal control model that explicitly accounts for decline or improvement in land quality over a period of 40 years is presented. The optimal area planted to trees and the optimal groundwater-table trajectory through time are determined under a variety of scenarios. Implications of the results for policy design are discussed.     

The emergence of forest age structures as determined by uneven-aged stands and age class forests

This article explores the question under which conditions trees are managed in even- or uneven-aged stands or age class forests, respectively. The problem of uneven-aged management within stands and forests can be reduced to the analysis of simultaneous optimal times of harvest and regeneration of interdependently growing trees. Restricting attention to a market environment, a forest investment model is developed which accounts for the opportunity to manage trees or stands individually. As a consequence, age class forests evolve as the optimal compromise between two opposing effects. They allow for a combination of the advantages of uneven-aged management by utilizing differences in tree growth on a larger scale and of even-aged management by exploiting locally effective positive inter-tree dependencies on a smaller scale. Accordingly, the emergence of the forest structure is determined by the dynamics in the balance of value growth and impact rate differences.     

Least-cost allocation of measures to increase the amount of coarse woody debris in forest estates

Coarse woody debris (CWD) is crucial for maintaining biodiversity in forests but conservation measures to increase CWD must be performed cost efficiently. We estimate least-cost combinations of CWD-increasing measures in a spruce-dominated Swedish forest estate. Specifically, we investigate how using combinations of the measures tree retention, creating high stumps, manual scarification, prolonged rotations, and retention of dying trees impacts the amount of CWD and net present value at the estate level. We found that by combining CWD-increasing measures in an optimal way the amount of CWD on the estate could be increased 322% with a decrease in present value of only 10%. The optimal combination of conservation measures depends on the desired increase in CWD. The analysis thus shows that huge improvements in cost-efficiency of biodiversity-oriented forestry are possible.     

Adapting the optimal selective-logging of Scots pine (Pinus sylvestris L.) stands in NE Spain to increasing CO2 concentrations

Predicted increases in CO₂ concentrations will affect forest ecosystems. In particular, they will impact tree growth, which in turn affects reproduction and mortality and consequently, forest planning. This study integrates different climate change scenarios of future biogeochemical processes and an economic model into a forest management model to determine the optimal selective-logging regime of Scots pine stands. It analyzes the economic implications of the management changes in comparison with the business as usual strategy. Adaption to new climatic conditions shows that it is optimal to increase the number of standing trees and to reduce the age of the logged trees. The results suggest that the failure to adapt the management regime has clear implications on the profitability of forests. Moreover, they show that higher mortality is likely to have a significant impact on the optimal forest management regime.     

海州湾单拖网渔船技术效率及其影响因素分析

在渔业资源衰退、渔船节能减排、渔业产业结构调整等多重压力下,短期内海洋捕捞业经济增长日趋困难。渔业技术效率是评价渔业经济增长质量的重要指标,界定其影响因素有助于促进资源优化配置,提高渔业经济增长水平。单拖网作业是中国近海一种重要捕捞方式,本文以海州湾70艘单拖网渔船为研究对象,利用DEA-Tobit模型,分析其技术效率及其影响因素。结果表明,仅有20.0%的海州湾单拖网渔船处于技术有效状态;渔船主机功率、渔船船体长度、渔船船龄以及燃油补贴对其技术效率的影响不显著;年出海天数、船长从业时间和年总成本对其技术效率有显著影响。     

The optimal selective logging regime and the Faustmann formula

This study analyzes the optimal selective logging regime of a size-distributed forest where individual trees compete for scarce resources such as space, light, and nutrients. The decision problem of the forest manager is formulated as a distributed optimal control problem. The interpretation of the first-order conditions allows a generalization of the Faustmann formula. In an empirical part, this article numerically determines the optimal management regime of a size-structured forest and shows that the optimal selective logging regime is associated with a normal forest under a wider variety of situations than stated in the previous literature.     

Designing afforestation subsidies that account for the benefits of carbon sequestration: A case study using data from China's Loess Plateau

This paper presents a method for determining the subsidy required to motivate farmers to participate in timber afforestation programs designed to maximize social well-being. The method incorporates a carbon sequestration benefit function into the land expected value model in order to quantify the social benefit arising from carbon sequestration by the planted trees. This is used to calculate the optimal rotation age for newly planted forests that maximizes social utility. The minimum subsidy required to motivate farmers to participate in the afforestation program was calculated using a modified decision model that accounts for the subsidy's impact. The maximum subsidy offered by the government was taken to be the NPV of the carbon sequestration achieved by afforestation. Data on Robinia pseudoacacia L. trees planted on the Loess Plateau were used in an empirical test of the model, which in this case predicts an optimal subsidy of 254.38 yuan/ha over 40 years. This would guarantee the maintenance of forest on land designated for afforestation until they reached the socially optimal rotation age. The method presented herein offers a new framework for designing afforestation subsidy programs that account for the environmental service (specially, the carbon sequestration) provided by forests.     

Adaptive management decision of agroforestry under timber price risk

In an effort to increase wood production and mitigate environmental problems, agro-forestry practices have emerged as a viable strategy in the Northern Plains of China, where one popular form of the agro-forestry system consists of fast-growing and high-yield plantation of poplar (populus) trees and the underwood planting of button mushroom (Agaricus bisporous). This paper examines adaptive management decision-making with stochastic dynamic programming under risk of timber price. Under the assumption of risk neutral preferences of the investors, the results suggest that the reservation price strategy remains optimal for the harvesting decision of agro-forests: when the timber price is higher than the reservation price, poplar trees should be harvested to end agro-forestry; otherwise, the trees should be retained. Numerical results are presented for sample agro-forest stands, which show that, with underwood planting, the reservation price for timber harvesting will be higher than that in pure forest.     

Economic Dynamics of Tree Planting for Carbon Uptake on Marginal Agricultural Lands

As a result of the 1997 Kyoto Protocol, afforestation of agricultural lands can be expected to take on an important role in the CO₂ emissions reduction policy arsenal of some countries. To date, identification of suitable (marginal) agricultural lands has been left mainly to foresters, but their criteria fail to take into account economic nuances. In this study, an optimal control model is used to determine the optimal level of afforestation in the western Canada. The results indicate that, while planting fast-growing trees for carbon uptake on marginal agricultural land may be important, the path dynamics matter in determining whether Canada can rely on afforestation to meet its obligations under Kyoto.
Sous l'impulsion duprotocole de Kyoto (1997), on peuts'attendre à voirle reboisement des terres agricoles prendre une place importante dans l'arsenal de mesures de réduction des émissions de CO₂ de certains pays. Jusqu'à présent, le choix des terres agricoles utilisables (c.-à-d. marginales pour l'agriculture) a été laissé principalement aux forestiers, mais les critères sur lesquels ces derniers se basent ne tiennent pas compte des aspects économiques. Nous utilisons ici un modèle de contrôle optimal pour déterminer le niveau optimal de reboisement qui conviendrait pour l'ouest du Canada. Il se dégage des résultats que, sans remettre en question l'importance de la plantation d'arbres à croissance rapide pour la capture du C dans les terres agricoles marginales, les décideurs devront tenir compte de la dynamique des sentiers avant que le reboisement puisse ètre la solution adoptée par le Canada pour honorer les engagements pris dans le cadre du Protocole.     

Application of the generalized Faustmann model to uneven-aged forest management

In this paper, a generalized Faustmann model is developed for uneven-aged management to allow the number of years and the level of residual growing stock to vary from one cutting cycle to the next. Comparative static analyses are conducted to determine the effect of changes in interest rate, stumpage price of the trees selected for harvest, the stumpage value of the residual growing stock, and the future land value on the decision variables. The model is then applied to study the uneven-aged management of a loblolly-shortleaf pine stand in south central U.S. to determine the length of the cutting cycle and the level of residual growing stock for the first cutting cycle as well as for a case involving four cutting cycles. Sensitivity analyses reveal that for the uneven-aged loblolly-shortleaf pine stand both the length of the cutting cycle and the level of the residual growing stock are very sensitive to changes in land value in the future, in the stumpage prices of trees selected for harvest, in the stumpage prices of the residual growing stock, and in the interest rate.     

The dynamics of phase farming in dryland salinity abatement

In Australia, soil salinisation has become a major concern. One way to deal with the problem is for farmers to plant trees or regenerate native bush. However, doing so raises several questions which involve optimal switching times, when switching involves a cost in the form of up-front investments. Optimality conditions are derived for the three-stage problem, and applied to dryland salinity control in Western Australia. Optimal management practices are found to be very sensitive to farmers' discount rates and to the speed at which the watertable rises or falls.     

Capturing benefits from water entitlement trade in salinity affected areas: A role for trading houses?

While there is potential for substantial benefits from water entitlement trade, external effects such as salinity may mean that traders cannot capture these benefits. This paper demonstrates that by creating a trading house as a single seller of water entitlements, with trade profits distributed to buyers, it is possible to achieve an allocation of entitlements which gives a social outcome higher than that possible from atomistic competition for entitlements. Such an outcome may be comparable to an optimally set uniform charge for water entitlements, but the trading house mechanism has the advantage that it makes use of trade to generate information on the optimal level of charging in the presence of salinity.     

The effect of site quality on economically optimal stand management

This paper proposes a discrete-time type timber harvesting model for simultaneously determining (i) the optimal quantity of seedlings to be planted, (ii) the optimal quantities of timber harvested by thinnings, and (iii) the optimal rotation age. With the help of Microsoft Excel Solver, a generalized reduced gradient algorithm, numerical examples are developed to evaluate the impact of the variations in the quality level of a forest site on the optimal harvest strategy. It is shown that the level of optimal rotation age and optimal quantity of seedlings to be planted can individually exhibit non-monotonicity to the increase in site quality.     

淄博市新型城镇化与农业现代化耦合度研究

［目的］新型城镇和农业现代化作为四化同步发展的重要组成部分,研究两者间的耦合度有利于区域甚至全国城乡经济社会一体化的发展。［方法］以淄博市为例,采用数据包络分析法对新型城镇化和农业现代化间的耦合度进行实证分析。［结果］2008—2017年淄博市新型城镇化和农业现代化协调发展的程度逐年增加,但一直处于次优水平,其中2008—2017年农业现代化推动新型城镇化的程度逐年增加,处于次优水平, 2008—2017年新型城镇化带动农业现代化的程度也逐年增加,同时2008—2015年处于次优水平2016—2017年处于最优水平; 同时2017年淄博市各区县新型城镇化和农业现代化协调度均处于次优水平,且新型城镇化带动农业现代化的程度相对于农业现代化推动新型城镇化的程度低,其中博山区、桓台县、高清县和沂源县的农业现代化推动新型城镇化的程度处于最优水平,其他区县处于次优水平,张店区的新型城镇化带动农业现代化的程度处于最优水平,其他区县处于次优水平。［结论］实现淄博市新型城镇化和农业现代化的均衡协调发展,必须加大农业现代化推动新型城镇化的程度,以核心区域辐射周边区县,进而促进两者的协调发展。     

Is native timber tree intercropping an economically feasible alternative for smallholder farmers in the Philippines?

Integration of trees on upland farms in the Philippines has been slower than expected and desirable from an environmental perspective. Our economic and risk analysis points to current policies as part of the problem. The study compares three domesticated indigenous timber trees (Shorea contorta V., Pterocarpus indicus J., and Vitex parviflora W.) intercropped with maize against a benchmark of the widely used exotic mahogany (Swietenia macrophylla K.). We used a biophysical simulation model (WaNuLCAS 3.1) to represent interaction between trees and crops for a fundamental level of water, nutrient and light capture as the basis for production functions. External conditions affecting systems profitability were accounted for in the Policy Analysis Matrix (PAM). Elements of risk were introduced through Monte Carlo simulation. Study results revealed that from a farmer’s perspective intercropping systems provide similar (within an uncertainty range of + or ? 10%) returns to monocropping scenarios. When net subsidies and taxes are accounted for, social profitability evaluations favour tree intercropping at high tree densities. The net effect of the current bias in price policies towards food production therefore refrains farmers from making decisions to integrate trees on farms; a decision that is actually in the national interest on economic grounds, even without consideration of positive environmental effects.     

Low-cost housing developments in South Africa miss the opportunities for household level urban greening

Most developing countries of the world are experiencing large-scale migration from rural to urban areas. Many new migrants end up in low-cost or informal areas and slums with attendant environmental concerns. One dimension of improved urban sustainability is the provision of green spaces and trees. Whilst many countries have urban greening programmes for public spaces and streets, few have considered the status and potential contribution of trees from resident's own gardens. This paper reports firstly on the policy environment for urban forestry and greening in South Africa and secondly on the maintenance, use and appreciation of trees on private homesteads of residents of new and older low-income suburbs as well as informal housing areas from three small towns in South Africa. In particular we examine if the most recent centrally planned and built low-income housing schemes (called RDP suburbs in South Africa) have considered and incorporated plans or spaces for urban greenery in peoples’ homesteads. We found that broad environmental and sustainability concerns and statements are common in urban development and housing policies, but specific guidelines for implementation are generally absent. More specifically, urban forestry and tree planting are rarely mentioned in the broader land use and environmental policies other than the national forest act and subsequent regulations, but even there it is relatively superficial. In the study towns the prevalence, density and number of species of trees was lowest in the new RDP suburbs relative to the township and informal areas. Consequently, the contribution of tree products to local livelihoods was also lower in the RDP areas. Yet there were no differences in the level of appreciation of the value and intangible benefits of trees between residents from the three different suburbs. This shows that the failure to plan for and accommodate trees in new low-cost housing developments is missing an opportunity to improve overall urban sustainability and liveability and constraining the potential flows of tangible and intangible benefits to urban residents. Making opportunities for such in older suburbs is challenging because of space limitations and cost implications of retrospective provisions, but incorporation into plans for new low-cost housing development should be possible.     

ASSESSMENTS OF THE RELATIVE VALUES OF COMPOUND NITROGEN-PHOSPHORUS FERTILIZERS FOR WHEAT PRODUCTION

A general procedure is developed for calculating optimal rates of application of compound fertilizers, containing several nutrients in fixed composition. The calculations are based on response surface models that have been obtained with single nutrient fertilizers. The relative values of alternative compounds can be assessed from the increases in profit that result from their use at optimal rates and this is preferable to simply comparing fertilizer compositions with that of an ideal mix of single nutrient fertilizers. The relative values of a range of standard nitrogen-phosphorus fertilizers are assessed for wheat production in southern New South Wales. The results indicate the need for a compound with a low nitrogen/phosphorus ratio of about 0.5. For the range of fertilizers considered it is concluded that it will generally be preferable to use superphosphate, supplementing with nitrogen fertilizer where N deficiency is suspected. The assumptions required for the calculation of optimal fertilizer rates are discussed.     

AN OPTIMAL CONTROL MODEL FOR INTEGRATED WEED MANAGEMENT UNDER HERBICIDE RESISTANCE*

The presence of weeds which have developed resistance to chemical herbicides is a problem of rapidly growing importance in Australian agriculture. We present an optimal control model of herbicide resistance development in ryegrass, the weed for which resistance is most commonly reported. The model is used to select the optimal combination of chemical and non-chemical control measures taking account of the trade off between short term profits and the long term level of herbicide resistance. Results indicate that given the threat of resistance there are benefits from integrating a combination of chemical and non-chemical control measures. The optimal strategy is found to include a declining herbicide dosage as resistance develops, with compensatory increases in the level of non-chemical control.     

Stimulating organic farming via publicly provided services and an auction-based subsidy

Governments generally use a mix of temporary hectare paymentsand provision of public services to stimulate the organic cropsector. In this paper, a conceptual model is developed for determininga socially optimal hectare payment for any given level of publicservices. Farm heterogeneity, due to the variability of soilquality and management skills, is explicitly taken into account.Using an nth price auction mechanism, farmers indicate whattheir reservation subsidy is for a given level of public inputprovision. The results of this auction are used to determinethe government's optimal policy choices.     

ECONOMIC ANALYSIS AND LIVESTOCK FEEDING

Much has been written about feeding eficiency as a major influence on projits in livestock production. Feed costs are shown to be the largest single item of cost and feeding eficiency to hinge on the twin problems of ascertaining the best level of yield for which to feed and of selecting those, feedstufs that produce the yield at least cost. Having demonstrated the incontrovertible logic of marginal analysis in the solution of these problems, agricultural economists tend to abandon the farmer to the task of putting theory into practice. While it is not disputed that a knowledge of principles may assist producers by delineating the information that is ideally required, the gul/ that exists betmeen theoretical principles and their practical application is a very real one, and is the concern of this paper in respect of the determination of optimal levels of output. After reviewing the manner in which the relevant theory applies to diferent types of livestock production practical problems are considered and possible solutions discussed.