Natural and anthropogenic geochemical signatures of floodplain and deltaic sedimentary strata, Sacramento-San Joaquin Delta, California, USA

The geochemical history of an upper deltaic plain pending tidal wetland restoration was reconstructed to assess remobilization of redox-sensitive constituents in sediment, identify depositional processes promoting geochemical retention, and determine the extent of contamination with Hg, As, Pb, Cu, and Zn. Three 12-14-m sediment cores were analyzed for bulk sediment geochemistry using ICP-AES. Rather than showing similar stratigraphic and geochemical down-core trends, cores had a unique record indicative of strong spatial gradients in deposition processes. Each strata type (e.g. basal clay, sand channel, distal floodplain, and agriculturally impacted surficial horizon) had a unique geochemical "fingerprint". The agriculturally impacted surficial layer showed high [Hg], [As], and [Pb]. The significance is that a restored upper delta will have a complex geomorphology defying conventional criteria of "success" in a restoration framework. Also, there is a significant risk of generating toxic, bio-available CH3Hg+ that would be hazardous to fish.     

B方针:拯救一颗行星与文明

地下水位下降,气温上升,水土流失和沙漠化,可能导致粮食价格的上涨.翻倍的谷物价格能够扰乱全球的经济发展,而且这也必然成为世界觉醒的召唤.从这一点看问题就很清楚:A方针--惯常的所做所为--再也不能继续下去了.B方针的3个原则构成是:提高全球水的生产率;中止人口增长;降低碳的排放以稳定气候.     

Gasoline prices and traffic crashes in alabama, 1999-2009

Objective: The price of gasoline has been found to be negatively associated with traffic crashes in a limited number of studies. However, most of the studies have focused either on fatal crashes only or on all crashes but measured over a very short time period. In this study, we examine gasoline price effects on all traffic crashes by demographic groups in the state of Alabama from 1999 to 2009. Methods: Using negative binomial regression techniques to examine monthly data from 1999 to 2009 in the state of Alabama, we estimate the effects of changes in gasoline price on changes in automobile crashes. We also examine how these effects differ by age group (16-20, 21-25, 26-30, 31-64, and 65+), gender (male and female), and race/ethnicity (non-Hispanic white, non-Hispanic black, and Hispanic). Results: The results show that gasoline prices have both short-term and long-term effects on reducing total traffic crashes and crashes of each age, gender, and race/ethnicity group (except Hispanic due to data limitations). The short-term and long-term effects are not statistically different for each individual demographic group. Gasoline prices have a stronger effect in reducing crashes involving drivers aged 16 to 20 than crashes involving drivers aged 31 to 64 and 65+ in the short term; the effects, however, are not statistically different across other demographic groups. Conclusions: Although gasoline price increases are not favored, our findings show that gasoline price increases (or decreases) are associated with reductions (or increases) in the incidence of traffic crashes. If gasoline prices had remained at the 1999 level of $1.41 from 1999 to 2009, applying the estimated elasticities would result in a predicted increase in total crashes of 169,492 (or 11.3%) from the actual number of crashes. If decision makers wish to reduce traffic crashes, increasing gasoline taxes is a possible option-however, doing so would increase travel costs and lead to equity concerns. These findings may help to shape transportation safety planning and policy making.     

Sea-level rise impacts on Africa and the effects of mitigation and adaptation: an application of DIVA

This paper assesses sea-level rise impacts on Africa at continental and national scales including the benefits of mitigation and of applying adaptation measures, considering four scenarios of global mean sea-level rises from 64 to 126 cm in the period of 1995–2100. We find that in 2100, 16–27 million people are expected to be flooded per year, and annual damage costs range between US5 and US 5 and US 9 billion, if no adaptation takes place. Mitigation reduces impacts by 11–36%. Adaptation in the form of building dikes to protect against coastal flooding and nourishing beaches to protect against coastal erosion reduces the number of people flooded by two orders of magnitude and cuts damage costs in half by 2100. Following such a protection strategy would require substantial investment. First, Africa’s current adaptation deficit with respect to coastal flooding would need to be addressed. DIVA suggests that a capital investment of US300 billion is required to build dikes adapted to the current surge regime and US 300 billion is required to build dikes adapted to the current surge regime and US 3 billion per year for maintenance. In addition, between US2 and US 2 and US 6 billion per year needs to be spent on protecting against future sea-level rise and socio-economic development by 2100. This suggests that protection is not effective from a monetary perspective but may still be desirable when also taking into account the avoided social impact. We conclude that this issue requires further investigation including sub-national scale studies that look at impacts and adaptation in conjunction with the development agenda and consider a wider range of adaptation options and strategies.     

H-Print: a new chemical fingerprinting approach for distinguishing primary production sources in Arctic ecosystems

The unambiguous identification of discrete sources of organic matter is critical for understanding the processes that affect ecosystem structure. Here, we demonstrate how changes in the relative proportions of highly branched isoprenoid lipids can provide a straightforward analytical method to distinguish between organic matter derived from sea ice and seawater within an Arctic ecosystem. In combination with stable isotope analysis, we reconstruct the organic matter pathway across trophic levels, thereby elucidating specific organic matter energy transfers. Combined, these methods will provide a useful analytical approach for determining ecosystem structure in the future. This is likely to become increasingly important as the Arctic continues to experience a phase of rapid climate change.     

Background level of risk determines the intensity of predator neophobia in juvenile convict cichlids

Behavioural ecology is rife with examples of prey animals that are able to adjust the intensity of their anti-predator response to match background risk levels. Often, preys need experience with predators before they will invest in costly anti-predator responses. This means that prey animals often fail to respond to predators during their first encounter. Recently, we have shown that prey raised under high-risk conditions may exhibit avoidance of potential predation cues independent of experience (neophobia). Such phenotypically plastic neophobic predator responses may reduce the initial costs of learning ecologically relevant threats while maintaining sufficient behavioural plasticity to respond to variation in local conditions. Here, we test if induced neophobia results in threat-sensitive behavioural trade-offs in response to a novel chemosensory cue. Our first experiment shows that while juvenile convict cichlids (Amatitlania nigrofasciata) pre-exposed to high (but not low) risk conditions exhibited predator avoidance to a novel odour (rainbow trout, Oncorhynchus mykiss), the response intensity was not influenced by the concentration of trout odour detected. Our second experiment demonstrated that the intensity of anti-predator response towards a novel predator cue was dependent upon the level of background risk. Convict cichlids pre-exposed to high-risk conditions showed stronger responses than those pre-exposed to low-risk conditions, while cichlids pre-exposed to intermediate-risk conditions exhibited intermediate response intensities. Together, these data demonstrate that background levels of risk and not the concentration of novel cues detected shape the induced neophobic response pattern of juvenile convict cichlids.