• Energy Research

AbstractEvidence is accumulating that species' responses to climate changes are best predicted by modelling the interaction of physiological limits, biotic processes and the effects of dispersal‐limitation. Using commercially harvested blacklip (Haliotis rubra) and greenlip abalone (Haliotis laevigata) as case studies, we determine the relative importance of accounting for interactions among physiology, metapopulation dynamics and exploitation in predictions of range (geographical occupancy) and abundance (spatially explicit density) under various climate change scenarios. Traditional correlative ecological niche models (ENM) predict that climate change will benefit the commercial exploitation of abalone by promoting increased abundances without any reduction in range size. However, models that account simultaneously for demographic processes and physiological responses to climate‐related factors result in future (and present) estimates of area of occupancy (AOO) and abundance that differ from those generated byENMs alone. Range expansion and population growth are unlikely for blacklip abalone because of important interactions between climate‐dependent mortality and metapopulation processes; in contrast, greenlip abalone should increase in abundance despite a contraction inAOO. The strongly non‐linear relationship between abalone population size andAOOhas important ramifications for the use ofENMpredictions that rely on metrics describing change in habitat area as proxies for extinction risk. These results show that predicting species' responses to climate change often require physiological information to understand climatic range determinants, and a metapopulation model that can make full use of this data to more realistically account for processes such as local extirpation, demographic rescue, source‐sink dynamics and dispersal‐limitation.

AbstractThe biosphere is changing rapidly due to human endeavour. Because ecological communities underlie networks of interacting species, changes that directly affect some species can have indirect effects on others. Accurate tools to predict these direct and indirect effects are therefore required to guide conservation strategies. However, most extinction‐risk studies only consider the direct effects of global change—such as predicting which species will breach their thermal limits under different warming scenarios—with predictions of trophic cascades and co‐extinction risks remaining mostly speculative. To predict the potential indirect effects of primary extinctions, data describing community interactions and network modelling can estimate how extinctions cascade through communities. While theoretical studies have demonstrated the usefulness of models in predicting how communities react to threats like climate change, few have applied such methods to real‐world communities. This gap partly reflects challenges in constructing trophic network models of real‐world food webs, highlighting the need to develop approaches for quantifying co‐extinction risk more accurately. We propose a framework for constructing ecological network models representing real‐world food webs in terrestrial ecosystems and subjecting these models to co‐extinction scenarios triggered by probable future environmental perturbations. Adopting our framework will improve estimates of how environmental perturbations affect whole ecological communities. Identifying species at risk of co‐extinction (or those that might trigger co‐extinctions) will also guide conservation interventions aiming to reduce the probability of co‐extinction cascades and additional species losses.

The Fukushima nuclear accident in March 2011 has increased social and political reluctance to embrace nuclear power in Japan (and elsewhere). The Japanese government has thus been considering four possible future energy mixes, including a nuclear-free pathway, and three others with 10%–35% nuclear supply coupled with a larger proportion of renewable energy and fossil fuels to replace nuclear. Here we use multi-criteria decision-making analysis (MCDMA) to assess the potential negative economic (levelised cost of electricity, and energy security), environmental (greenhouse-gas emissions, land transformation, water consumption, heated water discharge, air pollution, radioactive waste, and solid waste) and social (safety issues) impacts of the four proposed pathways to determine which scenario most holistically minimises adverse future outcomes. The nuclear-free pathway has the highest overall potential for adverse outcomes (score=2.49 out of 3), and the 35% nuclear power supply option yielding the lowest negative impact score (0.74) without weightings. Despite some sensitivity to the choice of criterion weights, our analyses demonstrate clearly that from an empirical perspective, a nuclear-free pathway for Japan is the worst option to pursue. We recommend that MCDMA methodology we used for Japan can be applied to other countries to evaluate future electricity generation scenarios.

South Korea is an important case study for understanding the future role of nuclear power in countries with on-going economic growth, and limited renewable energy resources. We compared quantitatively the sustainability of two ‘future-mapping’ exercises (the ‘Governmental’ scenario, which relies on fossil fuels, and the Greenpeace scenario, which emphasises renewable energy and excludes nuclear power). The comparison was based on a range of environmental and technological perspectives, and contrasted against two additional nuclear scenarios that instead envisage a dominant role for nuclear energy. Sustainability metrics included energy costs, external costs (greenhouse-gas emissions, air pollutants, land transformation, water consumption and discharge, and safety) and additional costs. The nuclear-centred scenarios yielded the lowest total cost per unit of final energy consumption by 2050 ($14.37 GJ−1), whereas the Greenpeace scenario has the highest ($25.36 GJ−1). We used probabilistic simulations based on multi-factor distributional sampling of impact and cost metrics to estimate the overlapping likelihoods among scenarios to understand the effect of parameter uncertainty on the integrated recommendations. Our simulation modelling implies that, despite inherent uncertainties, pursuing a large-scale expansion of nuclear-power capacity offers the most sustainable pathway for South Korea, and that adopting a nuclear-free pathway will be more costly and produce more greenhouse-gas emissions.

Marine biodiversity worldwide is under increasing threat, primarily as a result of over-harvesting, pollution and climate change. Chondrichthyan fishes (sharks, rays and chimaeras) have a perceived higher intrinsic risk of extinction compared to other fish. Direct fishing mortality has driven many declines, even though some smaller fisheries persist without associated declines. Mixed-species fisheries are of particular concern, as is illegal, unreported and unregulated (IUU) fishing. The lack of specific management and reporting mechanisms for the latter means that many chondrichthyans might already be susceptible to extinction from stochastic processes entirely unrelated to fishing pressure itself. Chondrichthyans might also suffer relatively more than other marine taxa from the effects of fishing and habitat loss and degradation given coastal habitat use for specific life stages. The effects of invasive species and pollution are as yet too poorly understood to predict their long-term role in affecting chondrichthyan population sizes. The spatial distribution of threatened chondrichthyan species under World Conservation Union (IUCN) Red List criteria are clustered mainly in (1) south-eastern South America; (2) western Europe and the Mediterranean; (3) western Africa; (4) South China Sea and Southeast Asia and (5) south-eastern Australia. To determine which ecological and life history traits predispose chondrichthyans to being IUCN Red-Listed, and to examine the role of particular human activities in exacerbating threat risk, we correlated extant marine species' Red List categorisation with available ecological (habitat type, temperature preference), life history (body length, range size) and human-relationship (whether commercially or game-fished, considered dangerous to humans) variables. Threat risk correlations were constructed using generalised linear mixed-effect models to account for phylogenetic relatedness. We also contrasted results for chondrichthyans to marine teleosts to test explicitly whether the former group is intrinsically more susceptible to extinction than fishes in general. Around 52% of chondrichthyans have been Red-Listed compared to only 8% of all marine teleosts; however, listed teleosts were in general placed more frequently into the higher-risk categories relative to chondrichthyans. IUCN threat risk in both taxa was positively correlated with body size and negatively correlated albeit weakly, with geographic range size. Even after accounting for the positive influence of size, Red-Listed teleosts were still more likely than chondrichthyans to be classified as threatened. We suggest that while sharks might not have necessarily experienced the same magnitude of deterministic decline as Red-Listed teleosts, their larger size and lower fecundity (not included in the analysis) predispose chondrichthyans to a higher risk of extinction overall. Removal of these large predators can elicit trophic cascades and destabilise the relative abundance of smaller species. Predator depletions can lead to permanent shifts in marine communities and alternate equilibrium states. Climate change might influence the phenology and physiology of some species, with the most probable response being changes in the timing of migrations and shifts in distribution. The synergistic effects among harvesting, habitat changes and climate-induced forcings are greatest for coastal chondrichthyans with specific habitat requirements and these are currently the most likely candidates for extinction. Management of shark populations must take into account the rate at which drivers of decline affect specific species. Only through the detailed collection of data describing demographic rates, habitat affinities, trophic linkages and geographic ranges, and how environmental stressors modify these, can extinction risk be more precisely estimated and reduced. The estimation of minimum viable population sizes, below which rapid extinction is more likely due to stochastic processes, is an important component of this endeavour and should accompany many of the current approaches used in shark management worldwide.

What are the most viable global pathways for a major expansion of zero-carbon emissions electricity sources given the diversity of regional technical, socio-political and economic constraints? We modelled a range of zero-emissions energy scenarios across nations that were designed to meet projected final energy demand in 2060, and optimised to derive the best globally aggregated results in terms of minimising costs and land use (a surrogate for environmental impacts). We found that a delayed energy transition to a zero-emissions pathway will decrease investment costs (−$3,431 billion), but increase cumulative CO2 emissions (additional 696 Gt). A renewable-only scenario would convert >7.4% of the global land area to energy production, whereas a maximum nuclear scenario would affect <0.4% of land area, including mining, spent-fuel storage, and buffer zones. Moreover, a nuclear-free pathway would involve up to a 50% greater cumulative capital investment compared to a high nuclear penetration scenario ($73.7 trillion). However, for some nations with a high current share of renewables and a low projected future energy demand (e.g., Norway), pursuit of a higher nuclear share is suboptimal. In terms of the time frame for replacement of fossil fuels, achieving a global nuclear share of about 50% by 2060 would be a technically and economically plausible target if progressing at a pace of the average historical growth of nuclear power penetration in France from 1970 to 1986 (0.28 MWh person−1 year-1). For effective climate-change mitigation, a high penetration of nuclear in association with a nationally appropriate mix of renewables achieves far superior cost and land effectiveness compared to a renewables-only future to reduce emissions.

The scientific evidence for anthropogenic climate change is empirically settled, but communicating it to nonscientific audiences remains challenging. To be explicit about the state of knowledge on climate science, the Intergovernmental Panel on Climate Change (IPCC) has adopted a vocabulary that ranks climate findings through certainty-calibrated qualifiers of confidence and likelihood. In this article, we quantified the occurrence of knowns and unknowns about "The Physical Science Basis" of the IPCC's Fifth Assessment Report by counting the frequency of calibrated qualifiers. We found that the tone of the IPCC's probabilistic language is remarkably conservative (mean confidence is medium, and mean likelihood is 66%-100% or 0-33%), and emanates from the IPCC recommendations themselves, complexity of climate research, and exposure to politically motivated debates. Leveraging communication of uncertainty with overwhelming scientific consensus about anthropogenic climate change should be one element of a wider reform, whereby the creation of an IPCC outreach working group could enhance the transmission of climate science to the panel's audiences. Supported by British Ecological Society research grant no. 4496–5470 to SH-P; Spanish Ministry of Economy, Industry and Competitiveness project no. CGL2013–40924-P to DRV; and Royal Society, Psychonomic Society, and Australian Research Council discovery project no. DP160103596 to SL.