Development of Safety Performance Functions for SafetyAnalyst Applications in Florida

In 2010, the American Association of State Highway and Transportation Officials (AASHTO) released a safety analysis software system known as SafetyAnalyst. SafetyAnalyst implements the empirical Bayes (EB) method, which requires the use of Safety Performance Functions (SPFs). The system is equipped with a set of national default SPFs, and the software calibrates the default SPFs to represent the agency’s safety performance. However, it is recommended that agencies generate agency-specific SPFs whenever possible. Many investigators support the view that the agency-specific SPFs represent the agency data better than the national default SPFs calibrated to agency data. Furthermore, it is believed that the crash trends in Florida are different from the states whose data were used to develop the national default SPFs. In this dissertation, Florida-specific SPFs were developed using the 2008 Roadway Characteristics Inventory (RCI) data and crash and traffic data from 2007-2010 for both total and fatal and injury (FI) crashes. The data were randomly divided into two sets, one for calibration (70% of the data) and another for validation (30% of the data). The negative binomial (NB) model was used to develop the Florida-specific SPFs for each of the subtypes of roadway segments, intersections and ramps, using the calibration data. Statistical goodness-of-fit tests were performed on the calibrated models, which were then validated using the validation data set. The results were compared in order to assess the transferability of the Florida-specific SPF models. The default SafetyAnalyst SPFs were calibrated to Florida data by adjusting the national default SPFs with local calibration factors. The performance of the Florida-specific SPFs and SafetyAnalyst default SPFs calibrated to Florida data were then compared using a number of methods, including visual plots and statistical goodness-of-fit tests. The plots of SPFs against the observed crash data were used to compare the prediction performance of the two models. Three goodness-of-fit tests, represented by the mean absolute deviance (MAD), the mean square prediction error (MSPE), and Freeman-Tukey R2 (R2FT), were also used for comparison in order to identify the better-fitting model. The results showed that Florida-specific SPFs yielded better prediction performance than the national default SPFs calibrated to Florida data. The performance of Florida-specific SPFs was further compared with that of the full SPFs, which include both traffic and geometric variables, in two major applications of SPFs, i.e., crash prediction and identification of high crash locations. The results showed that both SPF models yielded very similar performance in both applications. These empirical results support the use of the flow-only SPF models adopted in SafetyAnalyst, which require much less effort to develop compared to full SPFs.

Sex-biased differences in the effects of host individual, host population and environmental traits driving tick parasitism in red deer

The interactions between host individual, host population, and environmental factors modulate parasite abundance in a given host population. Since adult exophilic ticks are highly aggregated in red deer (Cervus elaphus) and this ungulate exhibits significant sexual size dimorphism, life history traits and segregation, we hypothesized that tick parasitism on males and hinds would be differentially influenced by each of these factors. To test the hypothesis, ticks from 306 red deer-182 males and 124 females-were collected during 7 years in a red deer population in south-central Spain. By using generalized linear models, with a negative binomial error distribution and a logarithmic link function, we modeled tick abundance on deer with 20 potential predictors. Three models were developed: one for red deer males, another for hinds, and one combining data for males and females and including "sex" as factor. Our rationale was that if tick burdens on males and hinds relate to the explanatory factors in a differential way, it is not possible to precisely and accurately predict the tick burden on one sex using the model fitted on the other sex, or with the model that combines data from both sexes. Our results showed that deer males were the primary target for ticks, the weight of each factor differed between sexes, and each sex specific model was not able to accurately predict burdens on the animals of the other sex. That is, results support for sex-biased differences. The higher weight of host individual and population factors in the model for males show that intrinsic deer factors more strongly explain tick burden than environmental host-seeking tick abundance. In contrast, environmental variables predominated in the models explaining tick burdens in hinds.

Exploratory spatial analysis of social and environmental factors associated with the incidence of Ross River Virus in Brisbane, Australia

We used geographic information systems and a spatial analysis approach to explore the pattern of Ross River virus (RRV) incidence in Brisbane, Australia. Climate, vegetation and socioeconomic data in 2001 were obtained from the Australian Bureau of Meteorology, the Brisbane City Council and the Australian Bureau of Statistics, respectively. Information on the RRV cases was obtained from the Queensland Department of Health. Spatial and multiple negative binomial regression models were used to identify the socioeconomic and environmental determinants of RRV transmission. The results show that RRV activity was primarily concentrated in the northeastern, northwestern, and southeastern regions in Brisbane. Multiple negative binomial regression models showed that the spatial pattern of RRV disease in Brisbane seemed to be determined by a combination of local ecologic, socioeconomic, and environmental factors.

Latitude variation in pancreatic cancer mortality in Australia

Objectives: Ecological studies support the hypothesis that there is an association between vitamin D and pancreatic cancer (PaCa) mortality, but observational studies are somewhat conflicting. We sought to contribute further data to this issue by analyzing the differences in PaCa mortality across the eastern states of Australia and investigating if there is a role of vitamin D-effective ultraviolet radiation (DUVR), which is related to latitude. ---------- Methods: Mortality data from 1968 to 2005 were sourced from the Australian General Record of Incidence and Mortality books. Negative binomial models were fitted to calculate the association between state and PaCa mortality. Clear sky monthly DUVR in each capital city was also modeled. ---------- Results: Mortality from PaCa was 10% higher in southern states than in Queensland, with those in Victoria recording the highest mortality risk (relative risk, 1.13; 95% confidence interval, 1.09-1.17). We found a highly significant association between DUVR and PaCa mortality, with an estimated 1.5% decrease in the risk per 10-kJ/m2 increase in yearly DUVR. ---------- Conclusions: These data show an association between latitude, DUVR, and PaCa mortality. Although this study cannot be used to infer causality, it supports the need for further investigations of a possible role of vitamin D in PaCa etiology.

Development of accident prediction models for rural highway intersections

A study was done to develop macrolevel crash prediction models that can be used to understand and identify effective countermeasures for improving signalized highway intersections and multilane stop-controlled highway intersections in rural areas. Poisson and negative binomial regression models were fit to intersection crash data from Georgia, California, and Michigan. To assess the suitability of the models, several goodness-of-fit measures were computed. The statistical models were then used to shed light on the relationships between crash occurrence and traffic and geometric features of the rural signalized intersections. The results revealed that traffic flow variables significantly affected the overall safety performance of the intersections regardless of intersection type and that the geometric features of intersections varied across intersection type and also influenced crash type.

Genetic Diversity of Rice Tungro Spherical Virus in Tungro-Endemic Provinces of the Philippines and Indonesia

The two adjacent genes of coat protein 1 and 2 of rice tungro spherical virus (RTSV) were amplified from total RNA extracts of serologically indistinguishable field isolates from the Philippines and Indonesia, using reverse transcriptase polymerase chain reaction (RT-PCR). Digestion with HindIII and BstYI restriction endonucleases differentiated the amplified DNA products into eight distinct coat protein genotypes. These genotypes were then used as indicators of virus diversity in the field. Inter- and intra-site diversities were determined over three cropping seasons. At each of the sites surveyed, one or two main genotypes prevailed together with other related minor or mixed genotypes that did not replace the main genotype over the sampling time. The cluster of genotypes found at the Philippines sites was significantly different from the one at the Indonesia sites, suggesting geographic isolation for virus populations. Phylogenetic studies based on the nucleotide sequences of 38 selected isolates confirm the spatial distribution of RTSV virus populations but show that gene flow may occur between populations. Under the present conditions, rice varieties do not seem to exert selective pressure on the virus populations. Based on the selective constraints in the coat protein amino acid sequences and the virus genetic composition per site, a negative selection model followed by random-sampling events due to vector transmissions is proposed to explain the inter-site diversity observed

Outbreak detection algorithms for seasonal disease data : a case study using Ross River virus disease

Background Detection of outbreaks is an important part of disease surveillance. Although many algorithms have been designed for detecting outbreaks, few have been specifically assessed against diseases that have distinct seasonal incidence patterns, such as those caused by vector-borne pathogens. Methods We applied five previously reported outbreak detection algorithms to Ross River virus (RRV) disease data (1991-2007) for the four local government areas (LGAs) of Brisbane, Emerald, Redland and Townsville in Queensland, Australia. The methods used were the Early Aberration Reporting System (EARS) C1, C2 and C3 methods, negative binomial cusum (NBC), historical limits method (HLM), Poisson outbreak detection (POD) method and the purely temporal SaTScan analysis. Seasonally-adjusted variants of the NBC and SaTScan methods were developed. Some of the algorithms were applied using a range of parameter values, resulting in 17 variants of the five algorithms. Results The 9,188 RRV disease notifications that occurred in the four selected regions over the study period showed marked seasonality, which adversely affected the performance of some of the outbreak detection algorithms. Most of the methods examined were able to detect the same major events. The exception was the seasonally-adjusted NBC methods that detected an excess of short signals. The NBC, POD and temporal SaTScan algorithms were the only methods that consistently had high true positive rates and low false positive and false negative rates across the four study areas. The timeliness of outbreak signals generated by each method was also compared but there was no consistency across outbreaks and LGAs. Conclusions This study has highlighted several issues associated with applying outbreak detection algorithms to seasonal disease data. In lieu of a true gold standard, a quantitative comparison is difficult and caution should be taken when interpreting the true positives, false positives, sensitivity and specificity.

Maternal pregravid body mass index and child hospital admissions in the first 5 years of life: results from an Australian birth cohort

Objectives: To examine the association of maternal pregravid body mass index (BMI) and child offspring, all-cause hospitalisations in the first 5 years of life. Methods: Prospective birth cohort study. From 2006 to 2011, 2779 pregnant women (2807 children) were enrolled in the Environments for Healthy Living: Griffith birth cohort study in South-East Queensland, Australia. Hospital delivery record and self-report baseline survey of maternal, household and demographic factors during pregnancy were linked to the Queensland Hospital Admitted Patients Data Collection from 1 November 2006 to 30 June 2012, for child admissions. Maternal pregravid BMI was classified as underweight (<18.5 kg m−2), normal weight (18.5–24.9 kg m−2), overweight (25.0–29.9 kg m−2) or obese (30 kg m−2). Main outcomes were the total number of child hospital admissions and ICD-10-AM diagnostic groupings in the first 5 years of life. Negative binomial regression models were calculated, adjusting for follow-up duration, demographic and health factors. The cohort comprised 8397.9 person years (PYs) follow-up. Results: Children of mothers who were classified as obese had an increased risk of all-cause hospital admissions in the first 5 years of life than the children of mothers with a normal BMI (adjusted rate ratio (RR) =1.48, 95% confidence interval 1.10–1.98). Conditions of the nervous system, infections, metabolic conditions, perinatal conditions, injuries and respiratory conditions were excessive, in both absolute and relative terms, for children of obese mothers, with RRs ranging from 1.3–4.0 (PYs adjusted). Children of mothers who were underweight were 1.8 times more likely to sustain an injury or poisoning than children of normal-weight mothers (PYs adjusted). Conclusion: Results suggest that if the intergenerational impact of maternal obesity (and similarly issues related to underweight) could be addressed, a significant reduction in child health care use, costs and public health burden would be likely.

Using simulation techniques to investigate methods to determine resistance of helminths to anthelmintic treatment

The widespread and increasing resistance of internal parasites to anthelmintic control is a serious problem for the Australian sheep and wool industry. As part of control programmes, laboratories use the Faecal Egg Count Reduction Test (FECRT) to determine resistance to anthelmintics. It is important to have confidence in the measure of resistance, not only for the producer planning a drenching programme but also for companies investigating the efficacy of their products. The determination of resistance and corresponding confidence limits as given in anthelmintic efficacy guidelines of the Standing Committee on Agriculture (SCA) is based on a number of assumptions. This study evaluated the appropriateness of these assumptions for typical data and compared the effectiveness of the standard FECRT procedure with the effectiveness of alternative procedures. Several sets of historical experimental data from sheep and goats were analysed to determine that a negative binomial distribution was a more appropriate distribution to describe pre-treatment helminth egg counts in faeces than a normal distribution. Simulated egg counts for control animals were generated stochastically from negative binomial distributions and those for treated animals from negative binomial and binomial distributions. Three methods for determining resistance when percent reduction is based on arithmetic means were applied. The first was that advocated in the SCA guidelines, the second similar to the first but basing the variance estimates on negative binomial distributions, and the third using Wadley’s method with the distribution of the response variate assumed negative binomial and a logit link transformation. These were also compared with a fourth method recommended by the International Co-operation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products (VICH) programme, in which percent reduction is based on the geometric means. A wide selection of parameters was investigated and for each set 1000 simulations run. Percent reduction and confidence limits were then calculated for the methods, together with the number of times in each set of 1000 simulations the theoretical percent reduction fell within the estimated confidence limits and the number of times resistance would have been said to occur. These simulations provide the basis for setting conditions under which the methods could be recommended. The authors show that given the distribution of helminth egg counts found in Queensland flocks, the method based on arithmetic not geometric means should be used and suggest that resistance be redefined as occurring when the upper level of percent reduction is less than 95%. At least ten animals per group are required in most circumstances, though even 20 may be insufficient where effectiveness of the product is close to the cut off point for defining resistance.

Evaluation of a Pound Net Leader Designed to Reduce Sea Turtle Bycatch

Offshore pound net leaders in the southern portion of Chesapeake Bay in Virginia waters were documented to incidentally take protected loggerhead, Caretta caretta, and Kemp’s ridley, Lepidochelys kempii, sea turtles. Because of these losses, NOAA’s National Marine Fisheries Service (NMFS) in 2004 closed the area to offshore pound net leaders annually from 6 May to 15 July and initiated a study of an experimental leader design that replaced the top two-thirds of the traditional mesh panel leader with vertical ropes (0.95 cm) spaced 61 cm apart. This experimental leader was tested on four pound net sites on the eastern shore of Chesapeake Bay in 2004 and 2005. During the 2 trial periods, 21 loggerhead and Kemp’s ridley sea turtles were found interacting with the control leader and 1 leatherback turtle, Dermochelys coriacea, was found interacting with the experimental leader. Results of a negative binomial regression analysis comparing the two leader designs found the experimental leader significantly reduced sea turtle interactions (p=0.03). Finfish were sampled from the pound nets in the study to assess finfish catch performance differences between the two leader designs. Although the conclusions from this element of the experiment are not robust, paired t-test and Wilcoxon signed rank test results determined no significant harvest weight difference between the two leaders. Kolmogorov-Smirnov tests did not reveal any substantive size selectivity differences between the two leaders.

Mortalities induced by the copepod Sinergasilus polycolpus in farmed silver and bighead carp in a reservoir

The frequency distributions of the parasitic copepod Sinergasilus polycolpus were examined in silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys nobilis during a disease outbreak of the 2 species of fish in a reservoir in China. The mean abundance of the copepod was positively related with host length and age, and the overdispersion of the copepod in both silver and bighead carp was fitted well with negative binomial distribution. Although parasite-induced host mortality was observed, a peaked age-parasite abundance curve was not detected in the present parasite-host system. It is also proposed that this peaked age-abundance curve is unlikely to be observed in its natural host populations.

Seasonal population dynamics of parasitic copepods, Sinergasilus spp. on farmed fish in China

Seasonal population dynamics of parasitic copepods in the genus Sinergasilus on fanned silver carp Hypophthalmichthys molitrix, farmed bighead carp Aristichthys nobilis, and grass carp Ctenopharyngodon idellus were investigated in China. Changes in prevalence and abundance were seasonal with higher levels observed in summer. Reproduction of the copepods occurs from spring to early autumn as indicated by the higher ratio of gravid copepods. The frequency distribution of Sinergasilus polycolpus and S. major in their host populations can be fitted well with negative binomial distribution. (C) 2000 Elsevier Science B.V. All rights reserved.

西藏齿突蟾蝌蚪冷适应策略研究

本文通过对高海拔两栖类西藏齿突蟾(Scutiger boulengeri)蝌蚪在实验室特定低温条件下的冷适应微空间行为分布的动态变化分析、温度耐受性实验及在不同适应温度的乳酸脱氢酶(LDH)同工酶的酶量与活性比较分析, 探讨了高海拔两栖类蝌蚪的部分冷适应策略。 西藏齿突蟾蝌蚪在不同温度的行为分布是一连续、动态过程，需用多种检验方法综合利用才能进行判断；在15℃, 除低海拔分布的西藏齿突蟾种群外所有实验物种蝌蚪均符合负二项分布、NeymanⅡ型分布；在10℃, 高海拔两栖类蝌蚪均符合负二项分布、NeymanⅡ型分布；在5℃、0℃低温时，高海拔两栖类不同分组的西藏齿突蟾蝌蚪的负二项分布、NeymanⅡ型分布均呈现明显差异, 这可能与高海拔两栖类蝌蚪在低温条件下通过不断地改变其行为分布方式来避免自身被冻伤有关。野外观察表明：高海拔两栖类蝌蚪常选择与流动河水相连的静水水体这种微生境中生存, 蝌蚪应对环境温度极端变化会不断改变其行为分布方式来选择最佳生存温度以避免极端高、低温对自身身体的伤害, 这种对微生境的利用能力对高海拔两栖类蝌蚪耐受极端环境温度的变化极其重要。 两栖类蝌蚪的温度耐受性实验表明不同的驯化温度可以改变西藏齿突蟾蝌蚪、两栖类仙琴水蛙蝌蚪的最适温度、逃避温度，并具有显著影响。 随着驯化温度5℃、10℃逐渐升高, 其最适温度、逃避温度也在一定范围内升高，但驯化温度对低海拔的仙琴水蛙蝌蚪的最适温度、逃避温度的改变效应大于高海拔的西藏齿突蟾蝌蚪的改变效应, 仙琴水蛙蝌蚪对温度的耐受范围、最适温度和逃避温度的ARRS值都大于西藏齿突蟾蝌蚪, 这说明仙琴水蛙蝌蚪对环境温度变化的适应能力大于西藏齿突蟾蝌蚪。 高海拔地区不同分组的两栖类蝌蚪, 在0℃适应温度时, LDH5条带的酶相对含量最高，而在5℃、10℃、15℃适应温度时，LDH5条带的酶相对含量明显都降低, 这表明酵解作用是高海拔两栖类蝌蚪的一些组织在低温﹑缺氧环境中的重要供能方式。高海拔两栖类蝌蚪同一分组的LDH总酶活性总是表现为10℃适应温度的总酶活性最高，而对低海拔的两栖类蝌蚪则是0℃适应温度的总酶活性最高, 这说明高海拔两栖类蝌蚪的LDH同工酶A、B两亚基基因活性在10℃时最高, 而低海拔两栖类蝌蚪的LDH同工酶A、B两亚基基因活性在0℃时最高。同时发现在15℃适应温度组的高海拔两栖类蝌蚪的LDH电泳图谱都有第6条带,有可能由LDH - C亚基组成, 对高海拔两栖类蝌蚪的LDH - C亚基只在15℃适应温度下才表达的机理还有待进一步的研究。 高海拔两栖类西藏齿突蟾蝌蚪通过行为分布方式的改变来选择最佳的生存温度, 这种温度选择过程与野外特定的微生境的存在密切相关, 现在由于人类对河道的不合理利用正在导致高海拔两栖类蝌蚪赖以生存的这种微生境逐渐消失, 这种微生境的消失将加速高海拔的两栖类种群数量衰退的进程。高海拔两栖类物种蝌蚪在低温（0℃）上表现出的同工酶多谱带说明，其A、B两亚基都有所表达，及其参与代谢的方式也是正常的，而低海拔两栖类物种蝌蚪只有A亚基表达的LDH5存在，因此其主要参与酵解过程，这种通过动物自身生理代谢方式的改变来适应极端环境温度条件的变化是高海拔两栖类蝌蚪能适应低温环境的重要策略。但高海拔物种的适应温度变化范围显著小于低海拔物种，对环境温度的变化适应能力有限，特别是对高温区域，因此全球气候变化可能对高海拔物种影响更为显著。 The partly cold-adaptation stratagem of the high altitude amphibian tadpole were researched in the laboratory by analyzing the high altitude amphibian tadpole of Scutiger boulengeri mainly on endpoints related to the dynamic variation of the micro-spatial behavior distribution patterns, the experiment of the temperature tolerance, and the enzyme content and activity of the lactic acid dehydrogenase(LDH) isozyme in special temperature condition. The behavior distribution of the Scutiger boulengeri tadpole is continuous and variable, but it can be figured out by multple testing ways. At 15℃, all of the experiment amphibian tadpoles behavior distribution fit both for the negative binomial distribution and NeymanⅡtype distribution except for the low altitude Scutiger boulengeri tadpoles. At 10℃, all of the high altitude amphibian tadpoles behavior distribution fit both for the negative binomial distribution and NeymanⅡtype distribution. At lower temperature, 5℃ and 0℃, the high altitude amphibian tadpoles of the Scutiger boulengeri at different groups behavior distribution fit for or don’t fit for behavior distribution respectively. It is denoted that the high altitude amphibian tadpoles probably avoid frostbiting by varying the behavior distribution patterns at low temperature condition. The high altitude amphibian tadpoles often actively select the special microhabitat which has the connected still water body and the flowing water body in the wild. It is important that tadpoles can endure the extreme temperature variety in this kind of microhabitat, because tadpoles can be better survival through select temperature condition through migrating in these kinds of microhabitats by varying their own behavior distribution patterns. Different acclimation temperature causes the significant change of preferred temperature(PT)、 avoiding temperature(AT) both in high altitude amphibian Scutiger boulengeri tadpoles and in low altitude amphibian Rana daunchina tadpoles in the temperature endurance experiment. With the acclimation temperature growing from 5℃ to 10℃. the PT and the AT of them would be uprise to some extent, but the effect of acclimation temperature on the PT and the AT of the tadpoles of Rana daunchina is more significant than the ones on the tadpoles of Scutiger boulengeri, at the same, the effects on the temperature endurance range, the ARRs of the tadpoles of Rana daunchina would be stronger than the ones on the tadpoles of Scutiger boulengeri. It is implied that the adaptation ability of tadpoles of Rana daunchina to the surroundings temperature alternation preferred to tadpoles of Scutiger boulengeri. At 0℃ acclimation temperature, the LDH5 enzyme comparative content of the high altitude amphibian tadpoles at different groups was highest, but it becomes lower at 5℃、10℃、15℃ acclimation temperature. It indicated that the alcoholysis role was the important ways of applying energy for special tissue of the high altitude amphibian tadpoles in low-temperature and low-oxygen condition. The total enzyme activity of the LDH of the high altitude amphibian tadpoles in the same group always keeps the highest at 10℃ acclimation temperature, but the low altitude amphibian tadpoles’ was maximum at 0℃. It was denoted that the gene activity of LDH -A and LDH – B submit was highest at 10℃ acclimation temperature for the high altitude amphibian tadpoles, but the low altitude amphibian tadpoles’ was maximum at 0℃. Meanwhile, the LDH electrophoretogram of the high altitude amphibian tadpoles always composed of 6 stripes at 15℃ acclimation temperature，the extra stripe probably was composed by LDH-C submit。It is unknown why LDH-C expresses only under high temperature。. The high altitude amphibian tadpoles can select the most optimal temperature by changing their behavior distribution patterns ceaselessly, but this course of selecting the most suitable temperature correlated with the special microhabitat in the wild closely. Nowadays, this kind of microhabitat which the high altitude amphibian tadpoles rely on are lossing gradually for human being exploit the riverway unreasonably. The disappearing of the microhabitat would accelerate the decline of the high altitude amphibian population. Compare to one band of LDH5, which only composed by the LDH-A submit, presents in the low altitude amphibian at 0℃, the five bands which composed by the LDH-A and LDH-B are checked out, this means the species which occurred in the highland is more adaptable to the low temperature. It is an important stratagem for the high altitude amphibian tadpoles adapt to the limited low temperature depends on the animal energy metabolism change.However, this kind of adaption is restricted, the adaption range to the temperature is much norrow in the high altitude amphibian than in the low one, especially for the high temperature side. The global climate change will be more serious for the high altitude species.

Seeing the forest for the fuel

We demonstrate a new approach to understanding the role of fuelwood in the rural household economy by applying insights from travel cost modeling to author-compiled household survey data and meso-scale environmental statistics from Ruteng Park in Flores, Indonesia. We characterize Manggarai farming households' fuelwood collection trips as inputs into household production of the utility yielding service of cooking and heating. The number of trips taken by households depends on the shadow price of fuelwood collection or the travel cost, which is endogenous. Econometric analyses using truncated negative binomial regression models and correcting for endogeneity show that the Manggarai are 'economically rational' about fuelwood collection and access to the forests for fuelwood makes substantial contributions to household welfare. Increasing cost of forest access, wealth, use of alternative fuels, ownership of kerosene stoves, trees on farm, park staff activity, primary schools and roads, and overall development could all reduce dependence on collecting fuelwood from forests. © 2004 Cambridge University Press.