Low-risk Scenarios Research Articles

Assessment of urbanization-induced ecological risks in an area with significant ecosystem services based on land use/cover change scenarios

ABSTRACTEcosystem services are facing numerous potential threats in rapidly developing areas. In this study, we investigated land use/cover change scenarios related to ecological risks due to urban development in an area with significant ecosystem services. Expansion of developed areas was considered as a risk source, and regional ecosystem services, such as soil conservation, soil erosion, and water conservation, were considered as risk receptors. Xiamen City was selected as a study case. Land-use and land-cover change processes in the study area were analyzed and used to predict future changes in urban spatial morphology. The analytic hierarchy process and ordered weighted averaging methods were employed to evaluation of urban comprehensive ecological risk and corresponding risk scenario settings. Most of northern and southern Xiamen City displayed a high level of ecosystem service under various high- or low-risk scenarios. Under the high-risk scenario, the average values of ecological risk due to newly developed land and total developed land were 0.402 and 0.324, respectively, in 2030 (power function exponent = 0.1). The average value of ecological risk due to newly developed land was generally higher than that caused by total developed land. In some local areas, such as Maluanwan and the small watershed Houxi, the ecological risk due to newly developed land was two to three times the average value for the entire study area. The results of this study provide an important reference for urban development.

The effects of securitized asset portfolio specialization on bank holding company’s return, and risk

Purpose The purpose of this paper is to examine the effect of specialization of the securitized assets portfolio on banks’ performance and securitization risk. In doing so, the paper addresses two important issues. First, whether the efficient risk–return trade-off for securitized asset portfolios is consistent with the principles of diversification. Second, whether the relationship between bank-level returns and securitized assets portfolio specialization is non-linear in securitization risk. Design/methodology/approach This paper used the fixed-effects panel regression model on US bank holding company data for the period 2001:Q2 to 2014:Q1. Findings The results show that securitized assets portfolio specialization increases returns and also reduces securitization default risk; banks’ return and securitized assets specialization are dependent in a non-linear manner on banks’ securitization risk. Additionally, it was also found that lower bank performance leads to higher securitization risk. Originality/value This paper is of value by demonstrating that diversification (specialization) of securitized assets portfolio would achieve better bank performance in low-risk (high-risk) scenarios.

Public Health Approaches and Barriers to Educating Providers about Hereditary Breast and Ovarian Cancer Syndrome.

The Michigan Department of Health and Human Services implemented and evaluated two initiatives designed to enhance provider knowledge of patients appropriate for breast and/or ovarian cancer genetic risk assessment and hereditary breast and ovarian cancer (HBOC) syndrome testing. The first initiative targeted select providers who had diagnosed patients meeting HBOC risk criteria. Specifically, the initiative used 2008–2009 state cancer registry data to identify all providers who had diagnosed breast cancers in women ≤50 years of age, male breast cancers, and ovarian cancers in four health systems with newly established cancer genetics clinics. Using a method coined bidirectional reporting (BDR), reports highlighting how many of these cases each provider had seen were generated and mailed. Reports on 475 cancers (9.5% of the 5005 cases statewide meeting criteria) were sent to 69 providers with information about how and why to refer such patients for genetic counseling. Providers who received a report were contacted to assess whether the reports increased awareness or resulted in action (genetic counseling/referral). Based on the few responses received, despite multiple attempts to contact, and attrition rate, it is not possible to ascertain the impact of this initiative on providers. However the project resulted in the MDHHS identifying which providers see the largest proportion of at-risk patients, creating an opportunity to target those providers with HBOC education efforts. The second initiative involved creating and broadly disseminating an online, interactive case-based educational module to increase awareness and referral decisions for HBOC using high- and low-risk patient scenarios. A total of 1835 unique users accessed the module in a one year. Collectively the users viewed topic pages 2724 times and the interactive case studies 1369 times. Point of care tools (fact sheets) were viewed 1624 times and downloaded 764 times. Satisfaction among the subset of users applying for continuing medical education credit was high. The online educational module had a much broader reach than the bidirectional reporting initiative but to a self-selected audience. Combining targeted and broad-based provider education efforts may be a better way to increase HBOC awareness in the target audience, starting with those providers seeing the largest proportion of patients at risk.

A Predictive Model of Driver Response in an Autonomous Environment

Remarkable strides have been made in the area of driving safety. Advanced technologies have successfully mitigated some crashes and there is a renewed belief that automation may be the solution to at least some of the remaining safety issues, particularly ones centered on human errors. Whilst automation is expected to be able to execute most longitudinal and lateral control tasks (Gold & Bengler, 2014), we do not yet know how effectively an automated driving suite (ADS) can re-integrate the human within the loop, especially in those situations where a driver’s response must be initiated quickly and is safety-critical. Successful transfer of control is made more complicated by various driver states (e.g., driver trust in automation, quality of calibration, and level of skill) and situational variables (e.g., sudden failure of the automation) that influence seamless transfer. The conceptual model proposed here, referred to as the AC/DC (Automatic Control/Driver Control) model and grounded in constructs of trust, calibration and ability, can be used to predict how a driver will respond in low and high risk scenarios when the automation fails suddenly and without warning. Such a model has the potential to expand our understanding of the complex interactions among different driver behavioral and situational factors that lead to particular responses and could inform interface design or human- automation control transfer protocols.

Comparative toxicities of organophosphate and pyrethroid insecticides to aquatic macroarthropods

As agricultural expansion and intensification increase to meet the growing global food demand, so too will insecticide use and thus the risk of non-target effects. Insecticide pollution poses a particular threat to aquatic macroarthropods, which play important functional roles in freshwater ecosystems. Thus, understanding the relative toxicities of insecticides to non-target functional groups is critical for predicting effects on ecosystem functions. We exposed two common macroarthropod predators, the crayfish Procambarus alleni and the water bug Belostoma flumineum, to three insecticides in each of two insecticide classes (three organophosphates: chlorpyrifos, malathion, and terbufos; and three pyrethroids: esfenvalerate, λ-cyhalothrin, and permethrin) to assess their toxicities. We generated 150 simulated environmental exposures using the US EPA Surface Water Contamination Calculator to determine the proportion of estimated peak environmental concentrations (EECs) that exceeded the US EPA level of concern (0.5×LC50) for non-endangered aquatic invertebrates. Organophosphate insecticides generated consistently low-risk exposure scenarios (EECs<0.5×LC50) for both P. alleni and B. flumineum. Pyrethroid exposure scenarios presented consistently high risk (EECs>0.5×LC50) to P. alleni, but not to B. flumineum, where only λ-cyhalothrin produced consistently high-risk exposures. Survival analyses demonstrated that insecticide class accounted for 55.7% and 91.1% of explained variance in P. alleni and B. flumineum survival, respectively. Thus, risk to non-target organisms is well predicted by pesticide class. Identifying insecticides that pose low risk to aquatic macroarthropods might help meet increased demands for food while mitigating against potential negative effects on ecosystem functions.

The relative roles of drive and empathy in self- and other-focused financial decision making

Can poor financial decisions be traced back to individual differences, and will individuals risk their own resources in the same manner as others’ resources? To help answer these questions, we assessed the relationship between other-focused financial risk, self-focused financial risk, and individual difference variables. 952 participants at a large university in the southeast U.S. completed questionnaires on the Behavioral Activation System Drive subscale (i.e., Drive) and dispositional Empathy. They were then presented with eight financial risk scenarios in a two-by-four within-subjects design. We found that individuals’ Drive – which is associated with facets of impulsivity – predicted increased likelihood of other-focused risk investment in scenarios with higher levels of risk and reward, above the effect of empathy. There was also some evidence that dispositional empathy also increased other-focused risk investment in scenarios with lower levels of risk and reward. We concluded that there is some evidence that empathy is an important factor for other-focused behavior in low-risk scenarios, but that drive is more important in higher-risk other-focused scenarios. Additionally, other-focused risk could be seen as more aversive than an equivalent amount of self-focused risk.

Sci-Sat AM: Stereo - 08: Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam

Purpose: To determine the feasibility of using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam for Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer. Methods and Materials: Ten anonymized patient CT data sets were used in this planning study. For each patient CT data set, three sets of contours were generated: 1) low risk, 2) intermediate risk, and 3) high risk scenarios. For each scenario, a single-arc and a double-arc VMAT treatment plans were created. Plans were generated with the Varian Eclipse™ treatment planning system for a Varian TrueBeam™ linac equipped with Millenium 120 MLC. Plans were created using a 10x-FFF beam with a maximum dose rate of 2400 MU/min. Dose prescription was 36.25Gy/5 fractions with the planning objective of covering 99% of the Planning Target Volume with the 95% of the prescription dose. Normal tissue constraints were based on provincial prostate SABR planning guidelines, derived from national and international prostate SABR protocols. Plans were evaluated and compared in terms of: 1) dosimetric plan quality, and 2) treatment delivery efficiency. Results: Both single-arc and double-arc VMAT plans were able to meet the planning goals for low, intermediate and high risk scenarios. No significant dosimetric differences were observed between the plans. However, the treatment time was significantly lower for a single-arc VMAT plans. Conclusions: Prostate SABR treatments are feasible with 10x-FFF VMAT technique. A single-arc VMAT offers equivalent dosimetric plan quality and a superior treatment delivery efficiency, compared to a double-arc VMAT.

Neural mechanisms of high‐risk decisions‐to‐drink in alcohol‐dependent women

A hallmark of alcohol dependence (AD) is continually drinking despite the risk of negative consequences. Currently, it is not known if the pattern of disordered activation in AD is more compatible with an over-sensitive reward system, a deficit in control systems or a combination of both to produce the high risk-taking behavior observed in alcohol dependents (ADs). Here, alcohol cues were used in an ecological decisions-to-drink task that involved high- and low-risk scenarios where the chance of serious negative imagined consequences was varied. Non-alcohol cues were included as control stimuli. Functional magnetic resonance imaging (fMRI) was used to measure blood oxygen level-dependent (BOLD) signal change in 15 alcohol-dependent and 16 control women. This design allowed us to address two major questions concerning AD: first, is there a specific pattern of disordered activation that drives the heightened endorsement of high-risk decisions-to-drink in ADs? And, second, is that pattern specific to decisions-to-drink or does it generalize to other appetitive and/or neutral cues? The results showed that, during high-risk decisions-to-drink, alcohol-dependent women activated reward circuits, cognitive control circuits and regions of the default-mode network (DMN), while control women deactivated approach circuits and showed enhanced activation in regions of the DMN. Group differences were found only for decisions-to-drink, suggesting that they are specific to alcohol cues. Simultaneous activation of reward networks, cognitive control networks and the DMN in alcohol-dependent women suggests that over-endorsement of high-risk drinking decisions by alcohol-dependent women may be due to a problem with switching between different neural networks.

Transcatheter aortic valve-in-surgical aortic valve implantation: current status and future perspectives

During the last decade, the relative use of surgical bioprosthetic valves has increased by nearly 80%, an observation likely explained by improved surgical techniques, valve durability, avoidance of anticoagulation and patient’s preference [1]. Nevertheless, surgical bioprosthetic valves are known to fail; actuarial freedom from reoperation for a failing bioprosthetic valve is 95, 90 and 70% at 5, 10 and 15 years, respectively [2, 3]. The lifetime risk of reoperation actually decreases with increasing patient age at the time of the index procedure. For example, a 50and a 60-year old patient undergoing surgical bioprosthetic aortic valve replacement will have a lifetime risk of reoperation of 45 and 25%, respectively [4]. The gold-standard treatment for a failing surgical bioprosthetic valve is a redo operation. The operative mortality following an elective redo operation in low-to-intermediate risk patients is 2–7% [5, 6]. In high surgical risk or non-elective cases, however, the mortality can be as high as 30% [7]. Even in low-risk and elective redo scenarios, the risks of wound infection, blood transfusions, postoperative pain and delayed functional recovery are not negligible. Transcatheter aortic valve-in-surgical aortic valve (TAV-in-SAV) implantation was first reported in 2007, and since then, numerous case series and registries have demonstrated its safety and efficacy [8, 9]. Since TAV-in-SAV avoids sternotomy and cardiopulmonary bypass, it can improve resource utilization by accelerating patient recovery and by reducing the length of hospital stay. Furthermore, it may obviate or reduce the number of repeat surgical procedures in a patient’s lifetime.

Sexual Behaviors, Decisional Balance, and Self-efficacy Among a Sample of Chinese College Students in the United States

Objectives: To assess sexual behaviors and condom use including perceived benefits, barriers, and self-efficacy among Chinese college students in the United States. Participants: One hundred thirty-three Chinese undergraduate and graduate students studying at 3 US universities. Methods: Self-report Internet questionnaire grounded in the Transtheoretical Model (TTM) framework analyzed with multivariate linear regression. Results: More than half (57.9%) have initiated sex. Only 27.3% used condoms every time. Frequent reasons for not using condoms were trust in partner, reduced pleasure, and partner dislike for condoms. Participants in the earlier TTM stages (precontemplation, contemplation, preparation) reported more worry about making partners angry if condoms were used and lower self-efficacy in situations involving alcohol or drug use and perceived low-risk scenarios. Conclusions: Interventions should increase condom availability to students and should also make condom use more acceptable, more often expected, and easier to discuss.

Reproductive Potential of Stable Flies (Diptera: Muscidae) Fed Cattle, Chicken, or Horse Blood

Reproductive potential was assessed for stable fly cohorts fed cattle, chicken, or horse blood. Flies provided chicken blood oviposited 20% more eggs per day than did those fed cattle or horse blood. However, flies provided cattle or horse blood were fecund 50% longer. When both egg viability and number of eggs produced were considered, lifetime reproductive potential was almost twice as high for flies fed cattle or chicken blood than for flies fed horse blood. Maternal investment, which took egg production and volume into account, was higher in cohorts fed cattle blood (70 mm3) when compared with the other treatments (chicken = 54 mm3, horse = 55 mm3). This is the first report of stable flies producing viable eggs after feeding on bird blood. Results from this study in addition to field observations indicate that stable fly interactions with birds may be limited to relatively low risk scenarios.

A mobility constraint model to infer sensor behaviour in forest fire risk monitoring

Wireless sensor networks (WSNs) play an important role in forest fire risk monitoring. Various applications are in operation. However, the use of mobile sensors in forest risk monitoring remains largely unexplored. Our research contributes to fill this gap by designing a model which abstracts mobility constraints within different types of contexts for the inference of mobile sensor behaviour. This behaviour is focused on achieving a suitable spatial coverage of the WSN when monitoring forest fire risk. The proposed mobility constraint model makes use of a Bayesian network approach and consists of three components: (1) a context typology describing different contexts in which a WSN monitors a dynamic phenomenon; (2) a context graph encoding probabilistic dependencies among variables of interest; and (3) contextual rules encoding expert knowledge and application requirements needed for the inference of sensor behaviour. As an illustration, the model is used to simulate the behaviour of a mobile WSN to obtain a suitable spatial coverage in low and high fire risk scenarios. It is shown that the implemented Bayesian network within the mobility constraint model can successfully infer behaviour such as sleeping sensors, moving sensors, or deploying more sensors to enhance spatial coverage. Furthermore, the mobility constraint model contributes towards mobile sensing in which the mobile sensor behaviour is driven by constraints on the state of the phenomenon and the sensing system.

Sexual behavior, stages of condom use, and self-efficacy among college students in Taiwan

The purposes of this study were: (1) to assess sexual behaviors and condom use behaviors; (2) to compare sexual behaviors and condom use behaviors between gender groups; and (3) to explore differences in specific items of self-efficacy to practicing condom use by the transtheoretical model stages of readiness to change among college students in Taiwan. A survey of students at two universities yielded 996 valid responses. The survey questions collected reports of demographic information, sexual history, condom use in general, and likely condom use in specific situations in relation to self-efficacy. Only 27.8% (n=277) reported ever having had sex, of these only 31.4% used condoms every time (those in action and maintenance). Condom use among women was lower than among men with men 5.1 times more likely to use condoms to prevent sexually transmitted infections (OR=5.1, 95% CI: 2.14–12.16, p=0.0002). The stages of change model with reported attitudes (self-efficacy) toward condom use in specific situations. The Tukey–Kramer multiple comparisons showed that participants in the maintenance stage reported significantly higher scores than those in the pre-contemplation, contemplation, and preparation stages for all 10 self-efficacy items (p<0.0001). Circumstances that are the most challenging for condom adherence across the stages are: partner preference to forego use, situations involving alcohol and drug use, and perceived low-risk scenarios. College students in Taiwan would benefit from targeted interventions that link risky sex to alcohol, and that address the interpersonal pressure within relationships that compel women students to practice unsafe sex.

Awareness and Utilization of BRCA1/2 Testing Among U.S. Primary Care Physicians

Testing for mutations in the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 (BRCA) has been commercially available since 1996. This study sought to determine, among U.S. primary care physicians, the level of awareness and utilization of BRCA testing and the 2005 U.S. Preventive Services Task Force (USPSTF) recommendations. In 2009, data were analyzed on 1500 physician respondents to the 2007 DocStyles national survey (515 family practitioners, 485 internists, 250 pediatricians, and 250 obstetricians/gynecologists). Overall, 87% of physicians were aware of BRCA testing, and 25% reported having ordered testing for at least one patient in the past year. Ordering tests was most prevalent among obstetricians/gynecologists in practice for more than 10 years, with more affluent patients. Physicians were asked to select indications for BRCA testing from seven different clinical scenarios representing increased (4) or low-risk (3) situations consistent with the USPSTF guidelines. Among ordering physicians (pediatricians excluded), 45% chose at least one low-risk scenario as an indication for BRCA testing. Only 19% correctly selected all of the increased-risk and none of the low-risk scenarios. A substantial majority of primary care physicians are aware of BRCA testing and many report having ordered at least one test within the past year. A minority, however, appear to consistently recognize the family history patterns identified by the USPSTF as appropriate indications for BRCA evaluation. These results suggest the need to improve providers' knowledge about existing recommendations-particularly in this era of increased BRCA direct-to-consumer marketing.

Ballast water risk assessment: principles, processes, and methods

Abstract Barry, S. C., Hayes, K. R., Hewitt, C. L., Behrens, H. L., Dragsund, E., and Bakke, S. M. 2008. Ballast water risk assessment: principles, processes, and methods. – ICES Journal of Marine Science, 65: 121–131. Two methods of assessing the risk of species introduction by ballast water are discussed, species-specific and environmental similarity assessments, each for alignment with four proposed principles of risk-based resource management: (i) society accepts that low risk scenarios exist; (ii) risk assessment is capable of identifying low risk scenarios; (iii) risk mitigation strategies exist; and (iv) mitigation costs are less than the cost of performing risk assessment. All four principles were met in some circumstances for both methods. Species-specific ballast water risk assessment is best suited to situations where the assessment can be restricted to a limited set of harmful species on journeys within bioregions where ballast water is a small component of natural genetic exchange. Environmental similarity risk assessment is appropriate for journeys that start and end in locations which have very little or no natural genetic exchange, such as journeys between non-contiguous bioregions. Because a large number of species are not assessed individually, environmental match assessments necessarily will be restricted to fundamental variables such as temperature and salinity. A number of bioregion classifications have been identified in the world’s oceans, some of which at a scale that may be appropriate for ballast water management. The suitability of any particular classification, however, needs further examination.

Automated Approach to Negotiations of BOT Contracts with the Consideration of Project Risk

The terms of concession including tariff and concession period are often discussed intensively during negotiations of build-operate-transfer (BOT) contracts. Based on prior studies on negotiation terms and risk of BOT contracts, this paper incorporates risk attributes of the BOT project into the formulation of a contractual-negotiation model. The proposed model allows the government and the sponsor to reach a consensus on the terms should the financial return as well as the risk of the project be determined. The pro forma cash flow of a BOT project is developed and used to generate the probability distribution of net present values (NPV) from the owner’s viewpoint by using Monte Carlo simulation. High- and low-risk scenarios are obtained to determine whether the contractual-negotiation models vary in accordance with risk levels. Results show that, given the expected NPV, the sponsor should be offered more favorable concessional terms for projects with high risk than that with low risk. We suggest that the government and industry practitioners embody the risk attributes of the project in the automated contractual-negotiation model.

What does my patient's coronary artery calcium score mean? Combining information from the coronary artery calcium score with information from conventional risk factors to estimate coronary heart disease risk.

BackgroundThe coronary artery calcium (CAC) score is an independent predictor of coronary heart disease. We sought to combine information from the CAC score with information from conventional cardiac risk factors to produce post-test risk estimates, and to determine whether the score may add clinically useful information.MethodsWe measured the independent cross-sectional associations between conventional cardiac risk factors and the CAC score among asymptomatic persons referred for non-contrast electron beam computed tomography. Using the resulting multivariable models and published CAC score-specific relative risk estimates, we estimated post-test coronary heart disease risk in a number of different scenarios.ResultsAmong 9341 asymptomatic study participants (age 35–88 years, 40% female), we found that conventional coronary heart disease risk factors including age, male sex, self-reported hypertension, diabetes and high cholesterol were independent predictors of the CAC score, and we used the resulting multivariable models for predicting post-test risk in a variety of scenarios. Our models predicted, for example, that a 60-year-old non-smoking non-diabetic women with hypertension and high cholesterol would have a 47% chance of having a CAC score of zero, reducing her 10-year risk estimate from 15% (per Framingham) to 6–9%; if her score were over 100, however (a 17% chance), her risk estimate would be markedly higher (25–51% in 10 years). In low risk scenarios, the CAC score is very likely to be zero or low, and unlikely to change management.ConclusionCombining information from the CAC score with information from conventional risk factors can change assessment of coronary heart disease risk to an extent that may be clinically important, especially when the pre-test 10-year risk estimate is intermediate. The attached spreadsheet makes these calculations easy.

Inflated perception of responsibility for harm in OCD patients with and without checking compulsions: a replication and extension

In a follow-up study to [J. Anxiety Disord., in press] examination of inflated perception of responsibility for harm among individuals with obsessive compulsive disorder (OCs), 22 OC checkers, 24 OC non-checkers, and 25 non-anxious controls (NACs) completed the Obsessive Compulsive Responsibility Scale (OCRS), which consisted of written descriptions of Low-Risk (LR), Moderate-Risk (MR), and High-Risk (HR) scenarios. In LR and MR scenarios, OC checkers reported greater perception of responsibility for harm and greater relief upon rectifying the situation, than did NACs. OC checkers also reported greater urges to rectify LR situations than did NACs. OC non-checkers did not differ from NACs on any of the scales. No group differences emerged for HR scenarios. The results suggest that, compared to OC non-checkers and to NACs, OC checkers have an inflated perception of responsibility for harm; and that this perception leads to a need to rectify potentially harmful situations.

Physician Preferences for Perioperative Anticoagulation in Patients With a Mechanical Heart Valve Who Are Undergoing Elective Noncardiac Surgery

To determine physicians' anticoagulation preferences in patients with a mechanical heart valve who are undergoing elective surgery, and to determine the effect of different risks of thromboembolism (TE) and postoperative bleeding on anticoagulation preferences. Mail survey of physicians who prescribe anticoagulant therapy. Physicians were asked to provide anticoagulation preferences in four clinical scenarios of patients with a mechanical heart valve who are undergoing elective surgery. Physicians were asked to select from three preoperative anticoagulation options (two aggressive, one less aggressive) and four postoperative anticoagulation options (two aggressive, two less aggressive). IV heparin was the most frequently selected anticoagulation option. Depending on the scenario, it was preferred by 39 to 79% of respondents for preoperative anticoagulation therapy, and by 44 to 84% of respondents for postoperative anticoagulant therapy. The risk of TE had a strong influence on anticoagulation preferences: more respondents preferred aggressive anticoagulant management in high-risk compared with low-risk TE scenarios (p < 0.001). Anticoagulation preferences were not influenced by the risk of bleeding: the proportion of respondents who preferred aggressive anticoagulant management did not differ in high-risk and low-risk bleeding scenarios (p > 0.05). Of respondents who preferred IV heparin for postoperative anticoagulation therapy, the risk of bleeding influenced the timing of heparin initiation: fewer respondents preferred early heparin initiation (within 12 h after surgery) in high-risk compared with low-risk bleeding scenarios (p < 0.01). (1) Preoperative and postoperative IV heparin were the most frequently selected anticoagulation options. (2) The risk of TE, but not the risk of bleeding, influenced the aggressiveness of anticoagulant management. (3) If IV heparin was selected, the risk of bleeding influenced the timing of heparin initiation.

Optimization of Rangeland Management Strategies under Rainfall and Price Risks

Dynamic programming was used to obtain optimal management and marketing policies for stocker operations in Southeastern Colorado under different stocking rates, rainfall, and price scenarios. Simulated steer liveweights at low, moderate, and high stocking rates were incorporated with simulated steer prices to maximize the present value of net returns from the sale of 0, 50, and 100% of the steer inventory in July, August, September, or October. Two low-risk, 1 moderate-risk, and 2 high-risk scenarios were considered. The 2 low-risk scenarios were favorable rainfall-optimistic price and favorable rainfall-pessimistic price. The moderate-risk scenario was average rainfall average price. The 2 high-risk scenarios were unfavorable rainfall-optimistic price and unfavorable rainfall-pessimistic price. The highest net returns from the low-risk and moderate-risk scenarios were obtained at the high stocking rate with sales in September and October. The highest net returns from the highrisk scenarios were obtained at the moderate stocking rate with sales in September and October. Risk-averse operators who are not prepared to handle sales before October will be better off using a low stocking rate. Risk-taker operators will obtain higher net returns than risk-averse operators using a high stocking rate providing they are prepared to sell half of the herd in July if cumulative rainfall up to June is below 149 mm. If this high stocking rate is maintained beyond July, operators should sell in September independently of the amount of rainfall or the level of prices in August.