The high cost of mutualism: effects of four species of East African ant symbionts on their myrmecophyte host tree

Three recent meta-analyses of protective plant-ant mutualisms report a surprisingly weak relationship between herbivore protection and measured demographic benefits to ant-plants, suggesting high tolerance for herbivory, substantial costs of ant-mediated defense, and/or benefits that are realized episodically rather than continuously. Experimental manipulations of protective ant-plant associations typically last for less than a year, yet virtually all specialized myrmecophytes are long-lived perennials for which the costs and benefits of maintaining ant symbionts could accrue at different rates over the host's lifetime. To complement long-term monitoring studies, we experimentally excluded each of four ant symbionts from their long-lived myrmecophyte host trees (Acacia drepanolobium) for 4.5 years. Ant species varied in their effectiveness against herbivores and in their effects on intermediate-term growth and reproduction, but the level of herbivore protection provided was a poor predictor of the net impact they had on host trees. Removal of the three Crematogaster species resulted in cumulative gains in host tree growth and/or reproduction over the course of the experiment, despite the fact that two of those species significantly reduce chronic herbivore damage. In contrast, although T. penzigi is a relatively poor defender, the low cost of maintaining this ant symbiont apparently eliminated negative impacts on overall tree growth and reproduction, resulting in enhanced allocation to new branch growth by the final census. Acacia drepanolobium is evidently highly tolerant of herbivory by insects and small browsers, and the costs of maintaining Crematogaster colonies exceeded the benefits received during the study. No experimental trees were killed by elephants, but elephant damage was uniquely associated with reduced tree growth, and at least one ant species (C. mimosae) strongly deterred elephant browsing. We hypothesize that rare but catastrophic damage by elephants may be more important than chronic herbivory in maintaining the costly myrmecophyte habit in this system.     

Green tenants: practicing a sustainability ethics for the rental housing sector

The shift towards social, government and corporate ethics which value environmental sustainability has also embraced householders in a plethora of educational guides, policies, regulations and consumer information about green home improvements, purchasing choices and household practices. In this paper, we make the claim that the rental housing sector, and in particular the private rental sector, has yet to participate, structurally, culturally and materially, in this shift to an ethics of sustainability. We argue, however, that even on such otherwise arid ground, an alternative ethic is developing, a sustainability ethic practiced by green tenants whose activities inside and outside their homes go beyond the considerable material constraints of their dwellings and incomes, and beyond the purely transactional utility of the rental contract. These activities, relational, interconnected and resilient, offer both glimpses of a greening rental housing sector, and a clearer picture of the areas where work remains to be done. Based on a research study, we conducted of the rental sector in regional Australia, and in particular of the everyday sustainability practices of tenants, we suggest that these activities are a practice-based form of care for the world, in many ways similar to Maria Puig de la Bellacasa's practice-based, human-decentred ethics which she suggests is exemplified in the permaculture movement. The stories of the tenants we interviewed for our study also point the way to other changes which are needed to enable a practice-based sustainability ethic to flourish across the rental housing sector as a whole.     

A conceptual model of the role of complex science in local authority consultations about air quality management

Abstract

There exists a clear imperative across the EU and within the UK towards the enhanced integration of community knowledge in environmental and health decision-making processes. The underlying social force that underpins this dynamic is the drive for a more accountable, transparent and publicly acceptable decision-making arena. However, relatively little research has been undertaken on the evaluation of local air quality management consultation in particular. In this context, the paper presents an evaluation of evidence resulting from questionnaire survey and case study research undertaken in the first round of the statutory process of local air quality management (LAQM), in which local authorities are required to consult on their air quality findings and intentions. We suggest that local authority perceptions of the relative abilities of differing stakeholders' grasp of air quality science, the process that translates that science into policy, and the institutional and organizational status of stakeholders (i.e. whether they are statutory or non-statutory stakeholders) may tend to transitively determine the choice of consultation methods used, the communication strategies chosen and the relative integration of stakeholder feedback into the LAQM decision-making process. In order to interrogate this potentially problematic chain of risk communication events, a preliminary conceptual model has been developed to enable the interrogation of the pathways through, and the obstacles to, the translation of air quality knowledge. The task is to unveil the sequential chains of association that comprise the LAQM risk communication process.     

Old ways for new days: Australian Indigenous peoples and climate change

ABSTRACT

This paper explores how Australia's Indigenous peoples understand and respond to climate change impacts on their traditional land and seas. Our results show that: (i) Indigenous peoples are observing modifications to their country due to climate change, and are doing so in both ancient and colonial time scales; (ii) the ways that climate change terminology is discursively understood and used is fundamental to achieving deep engagement and effective adaptive governance; (iii) Indigenous peoples in Australia exhibit a high level of agency via diverse approaches to climate adaptation; and (iv) humour is perceived as an important cultural component of engagement about climate change and adaptation. However, wider governance regimes consistently attempt to “upscale” Indigenous initiatives into their own culturally governed frameworks - or ignore them totally as they “don't fit” within neoliberal policy regimes. We argue that an opportunity exists to acknowledge the ways in which Indigenous peoples are agents of their own change, and to support the strategic localism of Indigenous adaptation approaches through tailored and place-based adaptation for traditional country.     

Detecting pigments from colourful eggshells of extinct birds

The known chemical basis of diverse avian eggshell coloration is generated by the same two classes of tetrapyrrole pigments in most living birds. We aimed to extend the evolutionary scope of these patterns by detecting pigments from extinct birds’ eggs. In our samples biliverdin was successfully extracted from subfossil shell fragments of the blue-green egg-laying upland moa Megalapteryx didinus, while protoporphyrin was extracted from the beige eggs of two other extinct moa species. Our data on pigment detection from eggshells of other extant paleognath birds, together with published information on other modern lineages, confirm tetrapyrroles as ubiquitous and conserved pigments contributing to diverse eggshell colours throughout avian evolution.     

Cost-Effective Reduction of NOx Emissions from Electricity Generation

ABSTRACT

This paper analyzes the benefits and costs of policies to reduce NO_x emissions from electricity generation in the United States. Because emissions of NOx contribute to the high concentration of atmospheric ozone in the eastern states associated with health hazards, the U.S. Environmental Protection Agency (EPA) has called on eastern states to formulate state implementation plans (SIPs) for reducing NO_x emissions. Our analysis considers three NO_x reduction scenarios: a summer seasonal cap in the eastern states covered by EPA's NO_x SIP Call, an annual cap in the same SIP Call region, and a national annual cap. All scenarios allow for emissions trading. Although EPA's current policy is to implement a seasonal cap in the SIP Call region, this analysis indicates that an annual cap in the SIP Call region would yield about $400 million more in net benefits (benefits less costs) than would a seasonal policy, based on particulate-related health effects only. An annual cap in the SIP Call region is also the policy that is most likely to achieve benefits in excess of costs. Consideration of omissions from this accounting, including the potential benefits from reductions in ozone concentrations, strengthens the finding that an annual program offers greater net benefits than does a seasonal program.     

Environmental whole farm management plans: their character, diversity, and use as agri-environmental indicators in New Zealand

This paper reports on a nationwide survey of environmental farm plan programmes and plan characteristics, towards determining New Zealand's (NZ's) capability and eligibility for reporting on the Organisation for Economic Cooperation and Development's (OECD) environmental whole farm management plan agri-environmental indicator. Considerations regarding the validity of the indicator are discussed. Environmental farm planning in NZ is widespread, fragmented, and diverse. Nine of NZ's 16 regional authorities have environmental farm plan programmes involving 20 different types of environmental farm plans. Potentially half of NZ's total area of farmland is included, but this is reduced by limited and selective use of environmental farm plans as policy instruments. Three authorities are capable of readily reporting the number and coverage of their environmental farm plans; six would need to manually compile the information. Compliance monitoring is mostly informal, but necessary for checking the implementation of plan works and actions. Eligibility of NZ environmental farm plans cannot be determined until the OECD define acceptance standards. A contemporary definition of environmental farm plans is proposed, along with additional criteria necessary to ensure such plans are credible indicators of issue ownership, adoption of best management practice, and landscape changes intended to improve environmental quality.     

Concentrations of ammonia and nitrogen dioxide at roadside verges, and their contribution to nitrogen deposition

Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.     

Erosion vs. recovery of coral reefs after 1998 El Niño: Chagos reefs, Indian Ocean

Three years after most corals died on the central Indian Ocean reefs of Chagos, erosion and recovery were studied to 30 m depth. Mortality was near-total to 15 m deep in northern atolls, and to > 35 m in central and southern atolls. Some reef surfaces have 'dropped' 1.5 m due to the loss of dense coral thickets. Coral bioerosion is substantial, reducing 3-D reef 'structure' and forming unconsolidated rubble. Juvenile corals are abundant, though mostly on eroding or unstable substrates, and are of less robust species. Reef fish abundance and diversity at 15 m depth remains high; species dependent on corals have diminished, while some herbivores and detritivores have increased. A new sea surface temperature (SST) data set shows that mean SST has risen 0.65 degree C since 1950. The critical SST causing the mortality in Chagos was 29.9 degrees C.