The effects of soil organic matter on soil water retention and plant water use in a meadow of the Sierra Nevada,CA

Tuolumne Meadows is a groundwater dependent ecosystem in the Sierra Nevada of California, USA, that is threatened by hydrologic impacts that may lead to a substantial loss of organic matter in the soil. In order to provide a scientific basis for management of this type of ecosystem, this paper quantifies the effect of soil organic content on soil water retention and water use by plants. First, we show a substantial dependence of soil water retention on soil organic content by correlating Van Genuchten soil water retention parameters with soil organic content, independent of soil texture. Then, we demonstrate the impact of organic content on plants by simulating the degree to which root water uptake is affected by soil water retention with the use of a physically based numerical model of variably saturated groundwater flow. Our results indicate that the increased water retention by soil organic matter contributes as much as 8.8 cm to transpiration, or 35 additional water‐stress free days, during the dry summer when plants experience increased water stress.     

Could working less reduce pressures on the environment? A cross-national panel analysis of OECD countries, 1970–2007

Many scholars and activists are now advocating a program of economic degrowth for developed countries in order to mitigate demands on the global environment. An increasingly prominent idea is that developed countries could achieve slower or zero economic growth in a socially sustainable way by reducing working hours. Research suggests that reduced working hours could contribute to sustainability by decreasing the scale of economic output and the environmental intensity of consumption patterns. Here, we investigate the effect of working hours on three environmental indicators: ecological footprint, carbon footprint, and carbon dioxide emissions. Using data for 1970–2007, our panel analysis of 29 high-income OECD countries indicates that working hours are significantly associated with greater environmental pressures and thus may be an attractive target for policies promoting environmental sustainability.     

Benthic control upon the morphology of transported fine sediments in a low‐gradient stream

The structure of fluvial sediments in streams has environmental implications to contaminant fate, nutrient budgeting and the carbon flux associated with fine particulate organic matter (FPOM). However, the influence of sediment structure is lacking in environmental predictive models. To this end, the present study links field‐based results of sediment aggregate structure to seasonal biological functions in the surface fine‐grained laminae (SFGL) of a low‐gradient stream. Fluvial sediment collection, microscopy and image analysis are used to show that aggregates collected over a 20 month time period support the concept that aggregate structure can vary seasonally in low‐gradient streams where temporarily stored sediment is prominent. Results show that the structure of the transported aggregates is more irregular in the summer with the structure being elongated about the long axes. In the winter, the aggregate structure is compacted and more spherical. Statistical analysis and results suggest that heterotrophic and autotrophic biological activity within the SFGL exhibits seasonal control upon the morphology of transported sediments. Implications of this research are highlighted through calculations of the reactive surface area of the transported suspended sediment load. The surface area of transported sediment is estimated to be 40% greater in the summer as compared to the winter time period, which implies that (i) the affinity of sediments to sorb contaminants is higher in summer months and (ii) the downstream reactivity of FPOM in large rivers, lakes and estuaries is not just a function of microbial drivers but also the seasonally dependent structure of transported FPOM derived from low‐order streams. Copyright © 2013 John Wiley & Sons, Ltd.     

Salmon aquaculture and coastal ecosystem health in Chile: Analysis of regulations,environmental impacts and bioremediation systems

In 2007 salmon, mollusk and seaweed aquaculture production in Chile totaled 904 thousand tonnes, making the nation the leading marine aquaculture producer in the western world. Salmonids grown in open cage net pens account for over 73% of the production. This review summarizes the current status of Chilean aquaculture and proposes the establishment of new regulations and monitoring programmes that encourage and accommodate emerging bioremediation technologies. In contrast to a rapidly expanding, well-financed and technologically advanced industry, the regulatory structure in Chile is outdated and based on insufficient science. The number of publications on the environmental impacts of salmon aquaculture in Chile is low relative to its production level. Nevertheless, the impacts of organic and inorganic waste on benthic communities, pelagic organisms and bird populations are documented. The technology to reduce these impacts using integrated multi-trophic aquaculture (IMTA) strategies exists, but has not been implemented at commercial scales. We call on the government and industry to support the creation of a well-financed and politically independent agency responsible for developing and enforcing science-based environmental regulations in Chile. The agency's immediate goal should be to fund research required to develop a transparent, ecosystem-based regulatory framework that promotes IMTA. Monitoring programs and licensing procedures must consider the impacts of individual sites and the cumulative impacts from multiple sites across a wide range of spatial scales. Before such changes are realized, environmental threats and human health risks will remain unacceptably high and salmon farming in Chile will not meet any reasonable definition of sustainability.     

Distinguishing sources of ground water recharge by using delta2H and delta18O

Stable isotope values of hydrogen and oxygen from precipitation and ground water samples were compared by using a volumetrically based mixing equation and stable isotope gradient to estimate the season and location of recharge in four basins. Stable isotopes were sampled at 11 precipitation sites of differing elevation during a 2-year period to quantify seasonal stable isotope contributions as a function of elevation. Supplemental stable isotope data collected by the International Atomic Energy Association during a 14-year period were used to reduce annual variability of the mean seasonal stable isotope data. The stable isotope elevation relationships and local precipitation elevation relationships were combined by using a digital elevation model to calculate the total volumetric contribution of water and stable isotope values as a function of elevation within the basins. The results of these precipitation calculations were compared to measured ground water stable isotope values at the major discharge points near the terminus of the basins. Volumetric precipitation contributions to recharge were adjusted to isolate contributing elevations. This procedure provides an improved representation of recharge contributions within the basins over conventional stable isotope methods. Stable isotope values from wells and springs at the terminus of each basin were used to infer the elevations of precipitation important for recharge of the regional ground water flow system. Ancillary climatic, geologic, and stable isotope values were used to further constrain the location where precipitation is entering the ground water flow system.     

Climate change adaptation advantage for African road infrastructure

The African continent is facing the potential of a $183.6 billion USD liability to repair and maintain roads damaged from temperature and precipitation changes directly related to predicted climate change through 2100. This cost is strictly to retain the current road inventory. This cost does not include costs associated with impacts to critically needed new roads. In many African countries, limited or non-existent funds for adaptation and mitigation are challenging these countries to identify the threats that are posed by climate change, develop adaptation approaches to the predicted changes, incorporate changes into mid-range and long-term development plans, and secure funding for the proposed and necessary adaptations. Existing studies have attempted to quantify the impact of climate change on infrastructure assets that will be affected by climate change in the coming decades. The current study extends these efforts by specifically addressing the effect of climate change on the African road infrastructure. The study identifies both total costs and opportunity costs of repairing and maintaining infrastructure due to increased stressors from climate change. Proactive and reactive costs are examined for six climate scenarios, with costs ranging, respectively, from an average of $22 million USD to $54 million USD annually per country. A regional analysis shows contrast between impacts in five areas of the continent, with impacts ranging from 22 % opportunity cost to 168 %. These costs have the potential to delay critical infrastructure development on the continent and present a challenge to policy makers balancing short-term needs with long-term planning.     

Justice forward: Tribes, climate adaptation and responsibility

Federally-recognized tribes must adapt to many ecological challenges arising from climate change, from the effects of glacier retreat on the habitats of culturally significant species to how sea leave rise forces human communities to relocate. The governmental and social institutions supporting tribes in adapting to climate change are often constrained by political obstructions, raising concerns about justice. Beyond typical uses of justice, which call attention to violations of formal rights or to considerations about the degree to which some populations may have caused anthropogenic climate change, a justice framework should guide how leaders, scientists and professionals of all heritages and who work with or for federally-recognized tribes understand what actions are morally essential for supporting tribes’ adaptation efforts. This paper motivates a shift to a forward-looking framework of justice. The framework situates justice within the systems of responsibilities that matter to tribes and many others, which range from webs of inter-species relationships to government-to-government partnerships. Justice is achieved when these systems of responsibilities operate in ways that support the continued flourishing of tribal communities.