Impacts of Experimentally Applied Mountain Biking and Hiking on Vegetation and Soil of a Deciduous Forest

Many recent trail degradation problems have been attributed to mountain biking because of its alleged capacity to do more damage than other activities, particularly hiking. This study compared the effects of experimentally applied mountain biking and hiking on the understory vegetation and soil of a deciduous forest. Five different intensities of biking and hiking (i.e., 0, 25, 75, 200 and 500 passes) were applied to 4-m-long × 1-m-wide lanes in Boyne Valley Provincial Park, Ontario, Canada. Measurements of plant stem density, species richness, and soil exposure were made before treatment, two weeks after treatment, and again one year after treatment. Biking and hiking generally had similar effects on vegetation and soil. Two weeks after treatment, stem density and species richness were reduced by up to 100% of pretreatment values. In addition, the amount of soil exposed increased by up to 54%. One year later, these treatment effects were no longer detectable. These results indicate that at a similar intensity of activity, the short-term impacts of mountain biking and hiking may not differ greatly in the undisturbed area of a deciduous forest habitat. The immediate impacts of both activities can be severe but rapid recovery should be expected when the activities are not allowed to continue. Implications of these results for trail recreation are discussed.     

Effects of Bridge Shading on Estuarine Marsh Benthic Invertebrate Community Structure and Function

The effect of bridge shading on estuarine marsh food webs was assessed by comparing benthic invertebrate communities beneath seven highway bridges with marshes outside of bridge-affected areas (reference marshes). We used light attenuation and height–width ratio (HW ratio), which takes into account the two main bridge characteristics that determine the degree of shading, to quantify the impact of shading on invertebrate communities. Low bridges, with HW ratio <0.7 and light attenuation greater than 85–90%, had benthic invertebrate densities and diversity that were significantly lower than reference marshes. Density of benthic invertebrates at low bridges was 25–52% (29,685–72,920 organisms/m²) of densities measured in adjacent reference marshes (119,329–173,351 organisms/m²). Likewise, there were fewer taxa under low bridges (5.8/11.35 cm² core) as compared to the reference marshes (9.0/11.35 cm² core). Density of numerically dominant taxa (e.g., oligochaetes and nematodes) as well as surface- and subsurface deposit feeders also were reduced under low bridges. Decreased invertebrate density, diversity, dominant taxa, and alterations of trophic feeding groups beneath low bridges was correlated with diminished above- and below-ground macrophyte biomass that presumably resulted in fewer food resources and available refuges from predators. With a greater knowledge of bridge shading effects, bridge construction and design may be improved to reduce the impacts on estuarine benthic invertebrate communities and overall ecosystem structure and function.     

Modeling the Fate and Transport of Plunging Inflows to Onondaga Lake

The transport and fate of two plunging tributaries, Onondaga and Ninemile Creeks, in Onondaga Lake, New York, are quantified based on application of hydrodynamic/transport models. Short‐term transport is simulated with a three‐dimensional Estuary Lake and Coastal Ocean Model (ELCOM), while the longer term fate is represented by a previously validated one‐dimensional model (UFILS4). The validation of ELCOM for the vertical distribution of tributary inflow into the lake's water column is demonstrated for four dye tracer experiments. The models are applied for three years to represent the dynamics of transport and fate for the two tributaries, with ELCOM predictions serving as input for UFILS4. The models together quantify the distribution of these inflows between the upper mixed layer (UML) and stratified depths, and the subsequent transport from stratified depths to the UML by vertical mixing. Substantial short‐term variations are predicted for both tributaries in response to variability in hydrology and weather. Increased inflow to the UML is predicted for high runoff periods. The fraction of Ninemile Creek's inflow directly entering the UML is predicted to be 50% greater than for Onondaga Creek due to Ninemile's lower negative buoyancy. The plunging phenomenon has important water quality implications, by reducing the effective loading to the UML, particularly for constituents with large rates of loss/transformation relative to the rate of vertical transport from stratified depths.     

Phosphorus Loadings Associated with a Park Tourist Attraction: Limnological Consequences of Feeding the Fish

The Linesville spillway of Pymatuning State Park is one of the most visited tourist attractions in Pennsylvania, USA, averaging more than 450,000 visitors · year⁻¹. Carp (Cyprinus carpio Linnaeus) and waterfowl congregate at the spillway where they are fed bread and other foods by park visitors. We hypothesized that the “breadthrowers” constitute a significant nutrient vector to the upper portion of Pymatuning Reservoir. In the summer of 2002, we estimated phosphorus loadings attributable to breadthrowers, and compared these values to background loadings from Linesville Creek, a major tributary to the upper reservoir. Items fed to fish included bread, donuts, bagels, canned corn, popcorn, corn chips, hot dogs, birthday cakes, and dog food. Phosphorus loading associated with park visitors feeding fish was estimated to be 3233 g day⁻¹, and estimated P export from the Linesville Creek watershed was 2235 g·day⁻¹. P loading attributable to breadthrowers exceeded that of the entire Linesville Creek watershed on 33 of the 35 days of study, with only a heavy rainfall event triggering watershed exports that exceeded spillway contributions. Averaged across 5 weeks, breadthrowers contributed 1.45-fold more P to Pymatuning Reservoir than the Linesville Creek watershed. If Linesville Creek P exports are extrapolated to the entire Sanctuary Lake watershed, spillway contributions of P added 48% to the non-point source watershed P entering the lake. Park visitors feeding fish at the Linesville Spillway are a significant source of nutrients entering Sanctuary Lake.     

The long time scales of the climate–economy feedback and the climatic cost of growth

This paper is based on the perception that the inertia of climate and socio-economic systems are key parameters in the climate change issue. In a first part, it develops and implements a new approach based on a simple integrated model with a particular focus on an innovative transient impact and adaptation modeling. In a second part, a climate–economy feedback is defined and characterized. The following results were found. 1) It has a long characteristic time, which lies between 50 and 100 years depending on the hypotheses; this time scale is long when compared to the system's other time scales, and the feedback cannot act as a natural damping process of climate change. 2) Mitigation has to be anticipated since the feedback of an emission reduction on the economy can be significant only after a 20-year delay and is really efficient only after at least 50 years. 3) Even discounted, production changes due to an action on emissions are significant over more than one century. 4) The methodology of the Intergovernmental Panel on Climate Change (IPCC), which neglects the feedback from impacts to emissions, is acceptable up to 2100, whatever is the level of impacts. This analysis allows also to define a climatic cost of growth as the additional climate change damages due to the additional emissions linked to economic growth.

Comparing Environmental Flow Implementation Options with Structured Decision Making: Case Study from the Willamette River,Oregon

Many frameworks have been used to identify environmental flows for sustaining river ecosystems or specific taxa in the face of widespread flow alteration. However, these frameworks largely focus on identifying suitable flows and often ignore the important links between management actions, resulting flows, and valued ecosystem or social responses. Structured decision making (SDM) could assist the comparison of environmental flows by providing a mature framework to link management actions to objectives via environmental flow science. We describe SDM and illustrate its application using a case study focused on comparing environmental flow scenarios for the mainstem Willamette River, Oregon. In a short timeframe, SDM was applied to identify objectives, develop empirical and expert opinion‐based models, and compare flow scenarios while accounting for interannual flow variability and partial controllability. No scenario was clearly preferred based on available knowledge, largely because river flows could only be partially controlled through dam operations. Participants agreed that SDM was useful for comparing alternative dam operations, but that refined predictive models and additional objectives were needed to better inform basinwide flow decisions. In our view, SDM can provide more realistic comparisons of environmental flows by accounting for partial controllability and uncertainty, which may result in greater implementation of available flow management actions.     

北京市大气污染减排潜力及居民健康效益评估

北京市能源消费正面临着污染物减排和保障居民健康的双重约束. 针对未来城市能源消费设计BAU(基准情景)和2个分别基于近期和中长期节能环保要求的受控情景(EC1、EC2),模拟预测了3个情景下主要大气污染物(SO₂、NO_x、PM₁₀、PM_2.5)在目标年(2020年)的排放水平,以确定大气污染减排潜力. 分别采用综合暴露-反应关系模型(IER)和泊松回归模型,评估北京市居民对PM_2.5暴露的健康风险,估算健康损失的经济价值. 结果表明:相较BAU情景,在EC1情景下, SO₂、NO_x、PM₁₀、PM_2.5减排率分别达到52.95%、49.77%、32.82%、41.41%,可减少PM_2.5暴露下居民死亡和发病219 783例,其中死亡1 295例、住院3 920例、门诊182 558例、患病32 011例,获得健康效益111.87×108元;在EC2情景下,SO₂、NO_x、PM₁₀、PM_2.5的减排率分别达到66.61%、63.42%、54.96%、57.44%,可减少PM_2.5暴露下居民死亡和发病519 234例,其中死亡2 930例、住院9 248例、门诊427 070例、患病79 986例,获得健康效益290.10×108元. 相较EC1情景,EC2情景可产生更大的减排潜力和居民健康效益. 从空间分布上来看,北京主城区因能源方案优化获得的健康效益较大,约占总健康经济效益的60%.      

我国海洋工程海洋环境影响后评价方法初探——以温州灵霓北堤工程海洋环境影响后评价为例

海洋工程竣工投产后,其造成的海洋环境负面影响往往超过工程施工前开展的海洋环境影响评价中的预测值,开展海洋工程海洋环境影响后评价工作是近几年来国外海洋发达国家海洋工程管理方面应用较为成熟的一种管理手段。温州灵霓北堤工程是我国首个实施海洋环境影响后评价的工程,在其竣工通车2 a后,为了检验灵霓北堤对瓯江口南北两侧海域的实际海洋环境影响以及前期环境评价单位,温州市发改委委托中国海洋大学展开环境影响后评价工作。中国海洋大学根据海域现状和历史调查资料,采用有无对比、前后对比和数学模型预测的方法,针对工程前期评价单位的预测与结论,评价了灵霓北堤两侧海域海洋环境质量现状,并对前期环评结论的合理性和正确性开展了分析。后评价结果表明,前期评价单位的预测结果基本都已得到体现,但其部分预测值较保守,例如部分区域的冲淤量和灵霓北堤对两侧生物的影响等。     

幕景分析法在累积影响评价中的实例应用研究

探讨了幕景分析方法在累积影响评谷中的应用途径，并将基于水质模型的幕景分析方法应用于水库投饵网箱养鱼项目，评价了累积影响的重大性，提出了相应的累积影响消减措施，其影响分析和评价结论对今后投饵网箱养鱼的环境管理具有重要价值，对建设项目EIA中增加累积影响 评价的内容提出建议。     

Life cycle assessment of a pulverized coal power plant with post-combustion capture, transport and storage of CO2

In this study the methodology of life cycle assessment has been used to assess the environmental impacts of three pulverized coal fired electricity supply chains with and without carbon capture and storage (CCS) on a cradle to grave basis. The chain with CCS comprises post-combustion CO₂ capture with monoethanolamine, compression, transport by pipeline and storage in a geological reservoir. The two reference chains represent sub-critical and state-of-the-art ultra supercritical pulverized coal fired electricity generation. For the three chains we have constructed a detailed greenhouse gas (GHG) balance, and disclosed environmental trade-offs and co-benefits due to CO₂ capture, transport and storage. Results show that, due to CCS, the GHG emissions per kWh are reduced substantially to 243 g/kWh. This is a reduction of 78 and 71% compared to the sub-critical and state-of-the-art power plant, respectively. The removal of CO₂ is partially offset by increased GHG emissions in up- and downstream processes, to a small extent (0.7 g/kWh) caused by the CCS infrastructure. An environmental co-benefit is expected following from the deeper reduction of hydrogen fluoride and hydrogen chloride emissions. Most notable environmental trade-offs are the increase in human toxicity, ozone layer depletion and fresh water ecotoxicity potential for which the CCS chain is outperformed by both other chains. The state-of-the-art power plant without CCS also shows a better score for the eutrophication, acidification and photochemical oxidation potential despite the deeper reduction of SO_x and NO_x in the CCS power plant. These reductions are offset by increased emissions in the life cycle due to the energy penalty and a factor five increase in NH₃ emissions.