Ecosystem research focuses on goods and services, thereby ascribing beneficial values to the ecosystems. Depending on the context, however, outputs from ecosystems can be both positive and negative. We examined how provisioning services of wild animals and plants can switch between being services and disservices. We studied agricultural communities in Laos to illustrate when and why these switches take place. Government restrictions on land use combined with economic and cultural changes have created perceptions of rodents and plants as problem species in some communities. In other communities that are maintaining shifting cultivation practices, the very same taxa were perceived as beneficial. We propose conversion factors that in a given context can determine where an individual taxon is located along a spectrum from ecosystem service to disservice, when, and for whom. We argue that the omission of disservices in ecosystem service accounts may lead governments to direct investments at inappropriate targets.
While the primary goal of environmental investigations is to assess and clean up contaminated properties, significant efforts are also directed towards resolving various matters in legal dispute. Opposing parties often disagree about the cause and timing of contamination and the associated liability and costs for meeting regulatory site closure requirements. Environmental experts are often needed to help resolve such legal disputes with expertise in hydrogeology, toxicology, microbiology, chemistry, engineering, and process safety. These experts, or teams of experts, provide technical approaches to determine the liability and cost apportionment amongst the various potentially responsible parties. Fate and transport models, environmental forensics, and risk assessment help to answer the issues in dispute. Skillful communication of these technical findings is needed to present conclusions to audiences that do not necessarily have technical backgrounds. 相似文献
The climate in Timor Leste (East Timor) is predicted to become about 1.5 °C warmer and about 10 % wetter on average by 2050. By the same year, the population is expected to triple from 1 to 2.5–3 million. This article maps the predicted changes in temperature and rainfall and reviews the implications of climate change and population growth on agricultural systems. Improved cultivars of maize, rice, cassava, sweet potato and peanuts with high yield performance have been introduced, but these will need to be augmented in the future with better adapted cultivars and new crops, such as food and fodder legumes and new management practices. The requirements for fertilizers to boost yields and terracing and/or contour hedgerows to prevent soil erosion of steeply sloping terrain are discussed. Contour hedges can also be used for fodder for improved animal production to provide protein to reduce malnutrition. 相似文献
As indoor smoking bans have become widely adopted, some U.S. communities are considering restricting smoking outdoors, creating a need for measurements of air pollution near smokers outdoors. Personal exposure experiments were conducted with four to five participants at six sidewalk bus stops located 1.5–3.3 m from the curb of two heavily traveled California arterial highways with 3300–5100 vehicles per hour. At each bus stop, a smoker in the group smoked a cigarette. Gravimetrically calibrated continuous monitors were used to measure fine particle concentrations (aerodynamic diameter ≤2.5 µm; PM2.5) in the breathing zones (within 0.2 m from the nose and mouth) of each participant. At each bus stop, ultrafine particles (UFP), wind speed, temperature, relative humidity, and traffic counts were also measured. For 13 cigarette experiments, the mean PM2.5 personal exposure of the nonsmoker seated 0.5 m from the smoker during a 5-min cigarette ranged from 15 to 153 µg/m3. Of four persons seated on the bench, the smoker received the highest PM2.5 breathing-zone exposure of 192 µg/m3. There was a strong proximity effect: nonsmokers at distances 0.5, 1.0, and 1.5 m from the smoker received mean PM2.5 personal exposures of 59, 40, and 28 µg/m3, respectively, compared with a background level of 1.7 µg/m3. Like the PM2.5 concentrations, UFP concentrations measured 0.5 m from the smoker increased abruptly when a cigarette started and decreased when the cigarette ended, averaging 44,500 particles/cm3 compared with the background level of 7200 particles/cm3. During nonsmoking periods, the UFP background concentrations showed occasional peaks due to traffic, whereas PM2.5 background concentrations were extremely low. The results indicate that a single cigarette smoked outdoors at a bus stop can cause PM2.5 and UFP concentrations near the smoker that are 16–35 and 6.2 times, respectively, higher than the background concentrations due to cars and trucks on an adjacent arterial highway.
Implications: Rules banning smoking indoors have been widely adopted in the United States and in many countries. Some communities are considering smoking bans that would apply to outdoor locations. Although many measurements are available of pollutant concentrations from secondhand smoke at indoor locations, few measurements are available of exposure to secondhand smoke outdoors. This study provides new data on exposure to fine and ultrafine particles from secondhand smoke near a smoker outdoors. The levels are compared with the exposure measured next to a highway. The findings are important for policies that might be developed for reducing exposure to secondhand smoke outdoors.相似文献
There have been conflicting accounts of the role and influence of local opposition within planning application outcomes for wind power developments. There is an expanding literature that considers public responses to proposed renewable energy developments and much of this suggests that public opposition is a key factor in the slow growth in renewable energy capacity. However, this paper will show that local opposition groups' power over such planning processes is very limited, and in fact extends only so far as delaying an outcome. Through a thematic content analysis of objection letters to one particular proposed wind power development, the key issues raised in connection with the development will be highlighted. Subsequently, these issues will be compared with those discussed in the official report of the planning appeals process, and it will be shown that the concerns of local objectors had little influence over the eventual verdict. 相似文献
Summary. Benzoic acid is a known stimulant of olfactory receptor cells in trichoid sensilla on the antennae of adult females of Bombyx mori. Exposure of freshly excised antennae, from B. mori females and males, to vapours of [14C]-benzoic acid revealed that the adsorbed acid is rapidly metabolized (15% conversion in 10 s), suggesting the presence of
a highly active enzymatic system. The major product could be identified as N-benzoylserine by use of [2H5]-benzoic acid, and mass spectrometry linked to a gas chromatograph (GC-MS) or a liquid chromatograph (LC-MS), for analysis
of the metabolites. The conjugation of benzoic acid with an amino acid apparently represents a novel mode for the rapid deactivation
of odorant molecules.
Received 26 March 2001. 相似文献
Personal exposure to air pollutants can be substantially higher in close proximity to an active source due to non-instantaneous mixing of emissions. The research presented in this paper quantifies this proximity effect for a non-buoyant source in 2 naturally ventilated homes in Northern California (CA), assessing its spatial and temporal variation and the influence of factors such as ventilation rate on its magnitude. To quantify how proximity to residential sources of indoor air pollutants affects human exposure, we performed 16 separate monitoring experiments in the living rooms of two detached single-family homes. CO (as a tracer gas) was released from a point source in the center of the room at a controlled emission rate for 5-12 h per experiment, while an array of 30-37 real-time monitors simultaneously measured CO concentrations with 15 s time resolution at radial distances ranging from 0.25-5 m under a range of ventilation conditions. Concentrations measured in close proximity (within 1 m) to the source were highly variable, with 5 min averages that typically varied by >100-fold. This variability was due to short-duration (<1 min) pollutant concentration peaks ("microplumes") that were frequently recorded in close proximity to the source. We decomposed the random microplume component from the total concentrations by subtracting predicted concentrations that assumed uniform, instantaneous mixing within the room and found that these microplumes can be modeled using a 3-parameter lognormal distribution. Average concentrations measured within 0.25 m of the source were 6-20 times as high as the predicted well-mixed concentrations. 相似文献
The Fourth International Conference on Fluidized Bed Combustion (FBC) was held at The MITRE Corporation in McLean, VA, December 9 to 11, 1975. With attendees from Great Britain, West Germany, Japan, Canada, and Sweden, the conference apparently fulfilled its international scope and intent. The objectives of the conference were to review the current state of technology in FBC, to promote technical information exchange on FBC and related areas, and to generate a useful technical information base for further FBC development. Throughout the conference, the goal of commercialization was repeatedly emphasized. Sponsored by the U.S. Energy Research and Development Administration (ERDA) and coordinated by MITRE, this meeting was the most comprehensive event in the seven year series of conferences on this subject according to attendees. ERDA, the government’s lead agency in FBC technology development, is the principal sponsor and coordinator of the National Fluidized Bed Combustion Program with the goal of advancing the commercialization time frame for FBC. Prior conferences in this series were hosted by the Environmental Protection Agency (EPA) at about two year intervals at Hueston Woods, Ohio. The last EPA conference was held in October 1972. 相似文献