Density derived estimates of standing crop and net primary production in the giant kelp <Emphasis Type="Italic">Macrocystis pyrifera</Emphasis>

Assemblages of macroalgae are believe to be among the most productive ecosystems in the world, yet difficulties in obtaining direct estimates of biomass and primary production have led to few macroalgal data sets from which the consequences of long-term change can be assessed. We evaluated the validity of using two easily measured population variables (frond density and plant density) to estimate the more difficult to measure variables of standing crop and net primary production (NPP) in the giant kelp Macrocystis pyrifera off southern California. Standing crop was much more strongly correlated to frond density than to plant density. Frond density data collected in summer were particularly useful for estimating annual NPP, explaining nearly 80% of the variation in the NPP from year to year. Data on frond densities also provided a relatively good estimate of seasonal NPP for the season that the data were collected. In contrast, estimates of seasonal and annual NPP derived from plant density data were less reliable. These results indicate that data on frond density collected at the proper time of year can make assessments of NPP by giant kelp more tractable. They also suggest that other easily measured variables that are strongly correlated with standing crop, such as surface canopy area, might serve as similarly useful proxies of NPP.     

Comparative assessment of coal tars obtained from 10 former manufactured gas plant sites in the eastern United States

A comparative analysis was performed on eleven coal tars obtained from former manufactured gas plant sites in the eastern United States. Bulk properties analyzed included percent ash, Karl Fisher water content, viscosity and average molecular weight. Chemical properties included monocyclic- and polycyclic-aromatic hydrocarbon (PAH) concentrations, alkylated aromatic concentrations, and concentrations of aliphatic and aromatic fractions. It was found that there was at least an order-of-magnitude variation in all properties measured between the eleven coal tars. Additionally, two coal tars obtained from the same manufactured gas plant site had very different properties, highlighting that there can be wide variations in coal tar properties from different samples obtained from the same site. Similarities were also observed between the coal tars. The relative chemical distributions were similar for all coal tars, and the coal tars predominantly consisted of PAHs, with naphthalene being the single-most prevalent compound. The C(9-22) aromatic fraction, an indicator of all PAHs up to a molecular weight of approximately 276 gmole(-1), showed a strong power-law relationship with the coal tar average molecular weight (MW (ct)). And the concentrations of individual PAHs decreased linearly as MW (ct) increased up to ca. 1000 gmole(-1), above which they remained low and variable. Implications of these properties and their variation with MW (ct) on groundwater quality are discussed. Ultimately, while these similarities do allow generalities to be made about coal tars, the wide range of coal tar bulk and chemical properties reported here highlights the complex nature of coal tars.     

Determining floodplain sedimentation rates using Cs in a low fallout environment dominated by channel- and cultivation-derived sediment inputs, central Queensland, Australia

Fallout ¹³⁷Cs has been widely used to determine floodplain sedimentation rates in temperate environments, particularly in the northern hemisphere. Its application in low fallout, tropical environments in the southern hemisphere has been limited. In this study we assess the utility of ¹³⁷Cs for determining rates of floodplain sedimentation in a dry-tropical catchment in central Queensland, Australia. Floodplain and reference site cores were analysed in two centimetre increments, depth profiles were produced and total ¹³⁷Cs inventories calculated from the detailed profile data. Information on the rates of ¹³⁷Cs migration through local soils was obtained from the reference site soil cores. This data was used in an advection–diffusion model to account of ¹³⁷Cs mobility in floodplain sediment cores. This allowed sedimentation rates to be determined without the first year of detection for ¹³⁷Cs being known and without having to assume that ¹³⁷Cs remains immobile following deposition. Caesium-137 depth profiles in this environment are demonstrated to be an effective way of determining floodplain sedimentation rates. The total ¹³⁷Cs inventory approach was found to be less successful, with only one of the three sites analysed being in unequivocal agreement with the depth profile results. The input of sediment from catchment sources that have little, or no, ¹³⁷Cs attached results in true depositional sites having total inventories that are not significantly different from those of undisturbed reference sites.     

The potential for adoption of climate smart agricultural practices in Sub-Saharan livestock systems

Livestock systems play an important role in the livelihoods of many rural communities in Sub-Saharan Africa while being responsible for an important share of human-induced greenhouse gas emissions. This study aimed to evaluate the potential for adoption of climate smart agricultural practices in Sub-Saharan livestock systems, related to the improvement in feed, animal husbandry, and grassland management. These practices present productivity and mitigation benefits and in some cases may also contribute to enhance resilience. In this study, we used a data set of 1538 farm households across nine Sub-Saharan countries. A mixed logit model was used to assess the influence on adoption and to estimate the probability of adoption. Our results show that there seems to be stronger influence of physical and financial capitals on adoption than the other capitals. Different types of capitals influence the uptake of different agricultural practices. Yet the probability of adoption would change across countries. The results of this study could help to refine adoption estimates calculated through global or regional modelling approaches and to inform the design of policies to better target investments in order to foster adoption.     

The Logical Foundations of Ecological Footprints

An academic debate about ecological footprints has started at last. It was set in motion by a critical article in Ecological Economics, 29(1), 61–72, by Jeroen C.J.M. van den Bergh and Harmen Verbruggen (henceforth B&V). Being ourselves major users of ecological footprints, we disagree with most of the criticisms that B&V level at the concept. In our experience, there are widespread misunderstandings surrounding the methodology of eco-footprinting, so it seems a good time to set out the logical foundations of eco-footprinting for all those who may have an interest in the subject – surely extending beyond the readers of Ecological Economics. Thus our approach will be a general exposition. However, even those who have not read the article by B&V will doubtless benefit from knowing the sort of criticisms which are made against ecological footprints, so we will also attempt to explain and respond to the criticisms raised by B&V.     

Can’t get there from here: attainable distance,sustainable intensification and full-scale technical potential

Full-scale technical potential provides a clear horizon for agricultural technology policy to meet the dual and urgent challenge of meeting food security and minimising the effects of climate change. A common stated goal is to double food production by 2050 to meet the needs of 9 billion people. The frontier of full-scale technical potential embodies this goal and provides a panacea for policy makers. However, the pathway between the present adoption of technologies towards this frontier is paved with some hazards which may be insurmountable. We develop a conceptual framework based on adoption levels of technology. The key criteria between current and potential adoption of technologies is the role of enablers, that is interventions which create changes in structural, distributional, technical, social and behavioural cultures. Policy must find optimal mixtures of regulation and voluntary mechanisms to fully encourage uptake of technologies and shift current adoption to meet full-scale technical potential. A range of technologies can be aligned with sustainable intensification and are examined in terms of this enabler framework. Further examination of the framework allows us to conclude that full-scale technical potential will never be achieved due to the stochastic nature of agricultural production, the diversity of motivations and institutional structures operating within food supply chains, as well as unbalanced cost-effectiveness criteria. We argue that sustainable intensification may provide a direction of travel for attaining food security but its poor conception, limited acceptability and understanding amongst the communities of interest lead to over-optimism in determining the journey to this final destination.     

Effects of knowledge,personal attribution and perception of ecosystem health on depreciative behaviors in the intertidal zone of Pacific Rim National Park and Reserve

Human activities levy a biological cost on ecosystems as resources are accessed and utilized at rates which are often incompatible with inherent ecosystem processes and structures. The recreational impact of humans upon intertidal zones and particularly fucoid algal assemblages is one major threat facing coastal ecosystems. The effect of human values, knowledge and perception in effecting biologically costly behaviors has rarely been examined. We hypothesize that with respect to intertidal zones: (1) Personal attribution and perception of ecosystem resiliency are more important than knowledge in determining the extent of depreciative behaviors individuals engage in, and; (2) Individuals who are uncertain about ecosystem resiliency will behave in a manner consistent with the 'precautionary principle'. We measured the depreciative behavior, and the attitudes and perceptions to ecosystem resilience, of visitors to Wick Headland in Pacific Rim National Park, British Columbia. Attitudes, knowledge, perceptions, and personal attribution were measured using questionnaire survey and structured interviews undertaken in situ. Depreciative behaviors of visitors were discreetly observed and correlated to the questionnaire survey and interview responses. We show that visitors who recorded greater knowledge of intertidal ecology engaged in more depreciative behaviors than visitors recording less knowledge. Visitors who perceived high ecosystem resilience in the intertidal zone engaged in significantly more behaviors eliciting biological cost than those who perceived low ecosystem resilience. Visitors who recorded uncertainty regarding ecosystem resilience engaged in significantly more depreciative behaviors than those who perceived low ecosystem resilience but slightly fewer depreciative behaviors than those who perceived high ecosystem resilience. Personal attribution was inversely correlated to the mean number of depreciative behaviors. We discuss the relevance of these results to the management of intertidal zones and marine protected areas, to multiple use management, the management of visitor impact, and natural resource use.