Nanoscale-targeted patch-clamp recordings of functional presynaptic ion channels

Important modulatory roles have been attributed to presynaptic NMDA receptors (NMDARs) located on cerebellar interneuron terminals. Evidence supporting a presynaptic location includes an increase in the frequency of mini events following the application of NMDA and gold particle-labelled NMDA receptor antibody localisation. However, more recent work, using calcium indicators, casts doubt on the idea of presynaptic NMDARs because basket cell varicosities did not show the expected calcium rise following either the local iontophoresis of L-aspartate or the two-photon uncaging of glutamate. (In theory such calcium imaging is sensitive enough to detect the calcium rise from even a single activated receptor.) It has therefore been suggested that the effects of NMDA are mediated via the activation of somatodendritic channels, which subsequently cause a subthreshold depolarization of the axon. Here we report results from a vibrodissociated preparation of cerebellar Purkinje cells, in which the interneuron cell bodies are no longer connected but many of their terminal varicosities remain attached and functional. This preparation can retain both inhibitory and excitatory inputs. We find that the application of NMDA increases the frequency of both types of synaptic event. The characteristics of these events suggest they can originate from interneuron, parallel fiber and even climbing fiber terminals. Interestingly, retrograde signalling seems to activate only the inhibitory terminals. Finally, antibody staining of these cells shows NMDAR-like immunoreactivity co-localised with synaptic markers. Since the Purkinje cells show no evidence of postsynaptic NMDAR-mediated currents, we conclude that functional NMDA receptors are located on presynaptic terminals

Using scenario analyses to address the future of food

The food system was developed around a set of policy drivers to make food cheaper and more available, these included promoting agricultural productivity and global trade to increase the availability of food. However, as has been recognised by a plethora of recent papers and reports, these factors have also led to a food system that is unsustainable through its impacts on human health (particularly the growing obesity epidemic) and the environment (e.g. as a major driver of climate change). The world is changing at an unprecedented rate, and the food system is becoming increasingly ‘just in time’, spatially extended, and dependent on more facilitating sectors (water, land, transport, finance, cyber, etc.). This produces a degree of systemic fragility that drivers (like demand) can interact with events (e.g. a climate impact) to create the opportunity for large-scale shifts in the way the world works. Given the unsustainability of the food system, and the uncertainty of how it may evolve, scenario analysis can be a useful tool for imagining plausible futures as an aid to unlocking ‘business as unusual’ thinking. Summarising a number of recent processes, I describe scenarios of countries’ food systems shaped by changing patterns of trade and changing dietary patterns

Scaling up pro-environmental agricultural practice using agglomeration payments: Proof of concept from an agent-based model

Rates of adoption of pro-environmental practices in agriculture in many parts of the world are low. In some cases, this is attributable to the private costs borne by farmers to adopt these practices, often well in advance of any benefits - public or private - that they may bring. Monetary incentives, such as through payments-for-ecosystem services (PES) programs, may be of assistance, and in this study we examine the potential for a recent innovation (the agglomeration payment) to improve adoption of pro-environmental practice in a rural agricultural context. Agglomeration payments include bonus payments for adoption by neighboring farms, which may help to encourage both compliance with the program they promote as well as the overall diffusion of the program across rural contexts. We develop an abstract agent-based model (ABM) of an agglomeration payment program to encourage adoption of the pro-environment practice of conservation agriculture (CA). We find that agglomeration payments have the potential to improve levels of adoption of pro-environmental practice per program dollar, and may help to reduce required spending on project monitoring and enforcement

The paradox of productivity: agricultural productivity promotes food system inefficiency

The principal policy focus for food has been to increase agricultural productivity and to liberalize markets allowing globalized trade. This focus has led to huge growth in the supply of agricultural produce, more calories becoming available, and price declining. The availability of cheaper calories increasingly underpins diets creating malnourishment through obesity, and global competition incentivizes producers who can produce the most, cheaply, typically with environmental damage. We propose re-focusing, away from yields per unit input, to the food system's overall productivity and efficiency-the number of people that can be fed healthily and sustainably per unit input. Since the Second World War, and particularly in recent decades, the over-Arching rationale of agricultural and food trade policy has been that by increasing the productivity of agriculture and efficiency of its markets, trade will drive down food prices, drive up choices and food availability: implicitly defining more available and cheaper food as the route to achieving the international public good of global food security. Here we hypothesize that a focus on increasing availability of food, and lowering food prices through focusing on agricultural productivity and trade does reduce prices and increases availability, but also encourages the externalization of costs on health and environment, and instead of providing public goods arguably represents market failure. In other words, a focus on increasing agricultural yields and efficiency decreases the efficiency of the food system through incentivizing externalization of costs. The focus should rather be on the efficiency of the food system to deliver profits, healthy diets and a healthy planet. Reframing the productivity argument towards the efficiency of the food system provides a clear route to reducing market failure, improving public health and sustainability

How well can body size represent effects of the environment on demographic rates? Disentangling correlated explanatory variables

1. Demographic rates are shaped by the interaction of past and current environments that individuals in a population experience. Past environments shape individual states via selection and plasticity, and fitness-related traits (e.g., individual size) are commonly used in demographic analyses to represent the effect of past22 environments on demographic rates. 2. We quantified how well the size of individuals captures the effects of a population’s past and current environments on demographic rates in a well-studied experimental system of soil mites. We decomposed these interrelated sources of variation with a novel method of multiple regression that is useful for understanding nonlinear relationships between responses and multicollinear explanatory variables. We graphically present the results using area-proportional Venn diagrams. Our novel method was developed by combining existing methods and expanding upon them. 3. We showed that the strength of size as a proxy for the past environment varied widely among vital rates. For instance, in this organism with an income breeding life-history, the environment had more effect on reproduction than individual size, but with substantial overlap indicating that size encompassed some of the effects of the past environment on fecundity. 4. This demonstrates that the strength of size as a proxy for the past environment can vary widely among life-history processes within a species, and this variation should be taken into consideration in trait-based demographic or individual-based approaches that focus on phenotypic traits as state variables. Furthermore, the strength of a proxy will depend on what state variable(s) and what demographic rate is being examined; i.e., different measures of body size (e.g., length, volume, mass, fat stores) will be better or worse proxies for various life-history processes

Eco-evolutionary dynamics. Experiments in a model system

Understanding the consequences of environmental change on both long- and short-term ecological and evolutionary dynamics is a basic pre-requisite for any effective conservation or management programme but inherently problematic because of the complex interplay between ecological and evolutionary processes. Components of such complexity have been described in isolation or within conceptual models on numerous occasions. What remains lacking are studies that characterise effectively the coupled ecological and evolutionary dynamics, to demonstrate feedback mechanisms that influence both phenotypic change, and its effects on population demography, in organisms with complex life histories. We present a systems-based approach that brings together multiple effects that 'shape' an organism's life history (e.g. direct and delayed life-history consequences of environmental variation) and the resulting eco-evolutionary population dynamics. Using soil mites in microcosms, we characterise ecological, phenotypic and evolutionary dynamics in replicated populations in response to experimental manipulations of environment (e.g. the competitive environment, female age, male quality). Our results demonstrate that population dynamics are complex and are affected by both plastic and evolved responses to past and present environments, and that the emergent population dynamic itself shaped the landscape for natural selection to act on in subsequent generations. Evolutionary and ecological effects on dynamics can therefore be almost impossible to partition, which needs to be considered and appreciated in research, management and conservation. © 2014 Elsevier Ltd

Conservation planning in agricultural landscapes: hotspots of conflict between agriculture and nature

Aim: Conservation conflict takes place where food production imposes a cost on wildlife conservation and vice versa. Where does conservation impose the maximum cost on production, by opposing the intensification and expansion of farmland? Where does conservation confer the maximum benefit on wildlife, by buffering and connecting protected areas with a habitable and permeable matrix of crop and non-crop habitat? Our aim was to map the costs and benefits of conservation versus production and thus to propose a conceptual framework for systematic conservation planning in agricultural landscapes. Location: World-wide. Methods: To quantify these costs and benefits, we used a geographic information system to sample the cropland of the world and map the proportion of non-crop habitat surrounding the cropland, the number of threatened vertebrates with potential to live in or move through the matrix and the yield gap of the cropland. We defined the potential for different types of conservation conflict in terms of interactions between habitat and yield (potential for expansion, intensification, both or neither). We used spatial scan statistics to find 'hotspots' of conservation conflict. Results: All of the 'hottest' hotspots of conservation conflict were in sub-Saharan Africa, which could have impacts on sustainable intensification in this region. Main conclusions: Systematic conservation planning could and should be used to identify hotspots of conservation conflict in agricultural landscapes, at multiple scales. The debate between 'land sharing' (extensive agriculture that is wildlife friendly) and 'land sparing' (intensive agriculture that is less wildlife friendly but also less extensive) could be resolved if sharing and sparing were used as different types of tool for resolving different types of conservation conflict (buffering and connecting protected areas by maintaining matrix quality, in different types of matrix). Therefore, both sharing and sparing should be prioritized in hotspots of conflict, in the context of countryside biogeography

Quantifying and modelling decay in forecast proficiency indicates the limits of transferability in land-cover classification

1. The ability to provide reliable projections for the current and future distribution of land-cover is fundamental if we wish to protect and manage our diminishing natural resources. Two inter-related revolutions make map productions feasible at unprecedented resolutions - the availability of high-resolution remotely-sensed data and the development of machine-learning algorithms. However, ground-truthed data needed for training models is in most cases spatially and temporally clustered. Therefore, map production requires extrapolation of models from one place to another and the uncertainty cost of such extrapolation is rarely explored. In other words, the focus has mainly been on projections, and less on quantifying their reliability. 2. Using the concept of ‘forecast horizon’, we suggest that the predictability of land-cover classification models should be quantitatively explored as a continuum against distances measured along multiple dimensions – space, time, environmental and spectral. Focusing on ten agricultural sites from England and using models specifically designed to predict multivariate decay-curves, we ask: how does a model’s predictive performance decay with distance? More specifically, we explored if we could predict the proficiency (kappa statistics) of a model trained in one site when making predictions in another site based on the spatial, temporal, spectral and environmental distances between sites. 3. We found that model proficiency decays with distance between sites in each dimension. More importantly, we found for the first time, that it is possible to predict the performance a model transferred to or from a novel site will have, based on its distances from known sites. The spatial distance variables were the most important when predicting model transferability. 4. Exploring model transferability as a continuum may have multiple usages including predicting uncertainty values in space and time, prioritization of strategies for ground-truth data collection, and optimizing model characteristics for defined tasks

Avian blood parasite infection during the non-breeding season: an overlooked issue in declining populations?

Background Pathogens and parasites can have major impacts on host population dynamics, both through direct mortality and via indirect effects. Both types of effect may be stronger in species whose populations are already under pressure. We investigated the potential for blood parasites to impact upon their hosts at the immunological, physiological and population level during the non-breeding season using a declining population of yellowhammers Emberiza citrinella as a model. Results Yellowhammers infected by Haemoproteus spp. showed both a reduced heterophil to lymphocyte (H:L) ratio, and an elevated standardised white blood cell (WBC) count compared to uninfected birds, indicating an immunological response to infection. Infected birds had shorter wings during the first winter of sampling but not during the second, colder, winter; survival analysis of 321 birds sampled across four winters indicated that increased wing length conferred a survival advantage. Conclusions We suggest that the potential impacts of blood parasite infections on over-wintering birds may have been underestimated. Further research should consider the potential impacts of sub-clinical parasite infections on the dynamics of vulnerable populations, and we suggest using declining populations as model systems within which to investigate these relationships as well as examining interactions between sub-clinical disease and other environmental stressors

Early adoption of conservation agriculture practices: Understanding partial compliance in programs with multiple adoption decisions

Land degradation and soil erosion have emerged as serious challenges to smallholder farmers throughout Southern Africa. To combat these challenges, conservation agriculture (CA) – a suite of agricultural practices consisting of zero tillage, mulching of crop residues, and intercropping with legumes – is widely promoted as a “sustainable” package of agricultural practices. Despite the many potential benefits of CA, however, adoption remains low. Yet relatively little is known about the decisionmaking process in choosing to adopt CA or any of its constituent practices. This article attempts to fill this important knowledge gap by studying CA adoption in southern Malawi. Unlike what is implicitly assumed when these packages of practices are introduced, farmers view adoption of CA as a series of separate decisions, rather than a single decision. But the adoption decisions need not be wholly independent. We find strong evidence of interrelated decisions, particularly among mulching crop residues and practicing zero tillage, suggesting that mulching residues and intercropping or rotating with legumes introduces a multiplier effect on the adoption of zero tillage