Key role for nuclear energy in global biodiversity conservation

Modern society uses massive amounts of energy. Usage rises as population and affluence increase, and energy production and use often have an impact on biodiversity or natural areas. To avoid a business-as-usual dependence on coal, oil, and gas over the coming decades, society must map out a future energy mix that incorporates alternative sources. This exercise can lead to radically different opinions on what a sustainable energy portfolio might entail, so an objective assessment of the relative costs and benefits of different energy sources is required. We evaluated the land use, emissions, climate, and cost implications of 3 published but divergent storylines for future energy production, none of which was optimal for all environmental and economic indicators. Using multicriteria decision-making analysis, we ranked 7 major electricity-generation sources (coal, gas, nuclear, biomass, hydro, wind, and solar) based on costs and benefits and tested the sensitivity of the rankings to biases stemming from contrasting philosophical ideals. Irrespective of weightings, nuclear and wind energy had the highest benefit-to-cost ratio. Although the environmental movement has historically rejected the nuclear energy option, new-generation reactor technologies that fully recycle waste and incorporate passive safety systems might resolve their concerns and ought to be more widely understood. Because there is no perfect energy source however, conservation professionals ultimately need to take an evidence-based approach to consider carefully the integrated effects of energy mixes on biodiversity conservation. Trade-offs and compromises are inevitable and require advocating energy mixes that minimize net environmental damage. Society cannot afford to risk wholesale failure to address energy-related biodiversity impacts because of preconceived notions and ideals. Un Papel Clave para la Energía Nuclear en la Conservación de la Biodiversidad Global La sociedad moderna usa cantidades masivas de energía y el uso de éstas incrementa conforme la población y la riqueza aumentan. La producción de energías y su uso continuamente han tenido un impacto sobre la biodiversidad o las áreas naturales. Para evitar la normalidad con la que se depende del carbón, el petróleo y el gas en las próximas décadas, la sociedad debe encontrar una futura mezcla de energías que incorpore fuentes alternativas. Este ejercicio puede llevar a opiniones radicalmente diferentes sobre lo que un portafolio de energías sustentables puede implicar, así que se requiera de una evaluación objetiva de los costos y beneficios relativos de las diferentes fuentes de energía. Evaluamos el uso de suelo, emisiones, clima e implicaciones de costo de tres líneas argumentales publicadas pero divergentes sobre el futuro de la producción de energía, ninguna de las cuales fue óptima para todos los indicadores ambientales y económicos. Al usar un análisis de toma de decisiones con criterios múltiples, ordenamos a siete fuentes generadoras de electricidad (carbón, gas, nuclear, biomasa, hidrológica, eólica y solar) con base en costos y beneficios y evaluamos la sensibilidad de las clasificaciones a sesgos originados de ideales filosóficos contrastantes. Sin importar las ponderaciones, la energía nuclear y la eólica tuvieron la relación costo-beneficio más alta. Aunque el movimiento ambiental históricamente ha rechazado la opción de la energía nuclear, la tecnología de reactores de nueva generación que reciclan completamente los desechos e incorporan sistemas pasivos de seguridad puede resolver las preocupaciones ambientalistas y debería ser entendido con mayor profundidad. Ya que no existen fuentes de energía perfectas, los profesionales de la conservación necesitan tener un enfoque basado en evidencias para considerar cuidadosamente los efectos integrados de la mezcla de energías sobre la conservación de la biodiversidad. Las compensaciones y los acuerdos mutuos son inevitables y requieren abogar por las mezclas de energía que minimicen el daño ambiental neto. La sociedad no puede permitirse el riesgo de un fracaso total en la señalización de impactos sobre la biodiversidad relacionados con la energía por causa de ideales y nociones preconcebidas. Over the last few centuries, civilization has become a vast and ceaselessly expanding consumer of energy, delivered primarily by fossil fuels (>80%)—coal, oil, and natural gas. The latest compiled data from 2011 show that approximately 550 exajoules (1 EJ = 1018 J) of primary energy were consumed by the global economy in that year (IEA 2013). Yet given the mounting threat of greenhouse gas-induced climate change and the chronic health impacts and energy-security problems associated with a reliance on burning fossil fuels, it is imperative that we seek substitute forms of energy supply in coming decades (Kharecha & Hansen 2013). In 2011, for global electricity generation (80 EJ of final energy in 2011), hydroelectric dams supplied the largest nonfossil component (15.8%), followed by nuclear (11.7%), wind (2.0%), biomass (1.9%), and solar power (0.3%) (IEA 2013). The transportation, mechanized agricultural, and industrial sector demands remain, for now, almost completely satisfied by fossil fuels. Forecasts point to a difficult transition (IPCC 2011). Energy use is set to continue to rise, driven largely by burgeoning demand for low-cost electricity in the developing world (Clarke et al. 2007). Moreover, extraction of a vast resource of environmentally damaging unconventional fossil fuels has begun (e.g., shale gas, tar sands, coal-seam gas) (Wigley 2011). Socioeconomic and technical momentum will make this trend toward cheap and readily available new fossil energy difficult to discourage and will require articulation of a well-planned, cost-competitive, and evidence-based alternative strategy (Mackay 2008; Nicholson 2012). If this energy future is to be relatively benign to nature, the costs and benefits of all competing energy forms will need to be carefully traded-off (Blees 2008). We argue that conservation professionals have a key role to play in this policy arena. For the least direct harm to biodiversity, the best energy options are those that use the least amount of land and fresh water (in production or mining), minimize pollution (e.g., carbon dioxide, aerosols, heavy metals, and toxic chemicals), restrict habitat fragmentation, and have a low risk of accidents that have large and lasting regional impacts on natural areas (e.g., oil spills, dam-burst floods, radioactive fallout). Yet the indirect effects of energy production are also critical. Conservation-friendly energy sources must also be cost-effective, reliable, and accessible relative to more environmentally damaging methods if they are to displace them. We reviewed the links between energy supply and biodiversity conservation, considered the potential and problems of some of the most widely touted nonfossil-fuel alternatives (renewable and nuclear), and devised a basic framework that can be used to rank and balance energy options objectively. Our goal was not to be overly prescriptive; rather, we sought to show why and how conservation scientists could engage most effectively in the energy-policy debate and so yield the best outcomes for global biodiversity. Conservation biologists readily acknowledge that 2 of the principal drivers of terrestrial biodiversity extinctions are habitat degradation and loss—mainly via agricultural expansion, logging, urbanization, and pollution (Brook et al. 2008). Climate disruption, and its synergies with other extinction drivers, will also continue to worsen over centuries and so strongly influence future species distributions (Bellard et al. 2012). Thus, it follows that anything humanity can do to mitigate climate warming, energy-related pollution, and land-use changes that negatively affect species will ultimately benefit biodiversity. Given that energy production from fossil fuels—for electricity, transportation, and industrial processes—is the principal source of anthropogenic greenhouse-gas emissions, biodiversity conservation is intrinsically intertwined with how we source our energy (Wiens et al. 2011). Cutting emissions is, however, only one aspect of the complex relationship between energy and biodiversity. For example, hydroelectricity dams are largely emissions-free after construction, but they can wreak havoc on local biodiversity through flooding and by obstructing migration (Dudgeon 2006). Globally, around 60% of the world's rivers were considered regulated in 2001; over 40,000 large dams (>100 have walls higher than 150 m) and their resulting reservoirs cover 500,000 km2 (McAllister et al. 2001). Other renewable energy sources are also land hungry (Wiens et al. 2011). Biofuels and wind energy in particular require land area per unit energy produced similar to hydroelectric dams (photovoltaic solar requires about 9 times less area per unit energy) (Supporting Information) (Pimentel & Pimentel 2007). Given that protected areas alone will be insufficient to safeguard biodiversity (Laurance et al. 2012), the conflict for space between energy production and habitat will remain one of the key future conservation issues to resolve. The demand for cropland production has been increasing by around 3.4 million ha/year, partly to keep pace with world's growing human population and consumption patterns (FAOSTAT 2009), which means that the additional burden of biofuel production could see increasingly larger areas commandeered for agriculture. For example, Stickler et al. (2007) estimate that 746 million ha of tropical forest are suitable for biofuel production (palm, soy, sugarcane) and if converted could provide 63% of global transportation fuel demand by 2030, releasing 443 Pg (1 Pg = 1015 g) of CO2 (Wiens et al. 2011). Land clearing for biofuel production also increases emissions from forest clearance (Mason Earles et al. 2012), removing the sequestration services of high-carbon-density forests and soils and increasing opportunity costs for conservation by raising land prices (Luyssaert et al. 2008). Indeed, the conversion of forests and peatlands to agriculture is responsible for about 15% of total human carbon emissions (Wiens et al. 2011). Slowing the conversion and fragmentation of primary forests and other relatively unscathed natural areas for energy production, while minimizing greenhouse gas emissions, is therefore a primary target for conservation science. It follows that land-use intensification for food (and possibly biofuel) production could minimize conflicts between human needs and biodiversity conservation if one or more cheap, abundant, and low-emissions energy sources were available to replace fossil fuels and so provide the majority of human needs. Highly intensified (and thus land-sparing) forms of agriculture, such as greenhouses, vertical farms, and hydroponic facilities, require substantial inputs of artificial energy, synthetized nutrients, and desalinated water, which must be supplied by clean-energy sources to be considered sustainable and low impact. The forecasting reported in the IEA (2013) World Energy Outlook projects an ongoing dominance of coal, oil, and gas for at least the next 5 decades, and only minor mitigation policies have been implemented to date. This business-as-usual (BAU) with new-policies scenario (implementing already announced national energy plans) described by the International Energy Agency assumes ongoing energy-demand growth, due to increasing human population and affluence (Bradshaw & Brook 2014), with the greatest expansion coming from Asia and developing nations. Concomitant with this scenario is an enormous rise in greenhouse-gas emissions. The Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC 2013) predicts global warming of 2.6–4.8 °C by 2081–2100 under the most emissions-intensive energy scenario (RCP8.5). What might an alternative and more biodiversity-friendly future scenario look like? Although an almost infinite variety of future energy mixes is possible, most are implausible on the grounds of cost, technological maturity, capacity to operate at large scales, reliability, social acceptance, and the pragmatic need to manage infrastructure transitions incrementally (Smil 2010). For illustrative purposes, we refer to 2 alternative energy production scenarios that differ substantially from the BAU scenario but nevertheless have credibility (i.e., deemed plausible in the peer-reviewed literature): a high renewable-energy mix that excludes nuclear power and assumes massive gains in energy efficiency that leads to a lower overall demand (Greenpeace 2012) and an energy mix with a large nuclear-energy contribution, smaller contributions from a mix of renewables and fossil fuels, and carbon capture and storage (Brook 2012). The proportional energy breakdowns (in terms of electricity generation) and resulting greenhouse-gas emissions for these 3 scenarios are shown in Fig. 1. 3 scenarios ongoing and substantial in We the most impacts of these scenarios to the total global electricity demand for and land area by production infrastructure wind and solar farms, hydroelectric and for fuel not for greenhouse-gas emissions from energy production of the amount of climate warming by (IPCC 2013) based on the of the for the BAU scenario and for the 2 and the cost of the 3 Given the of all potential effects of energy production on biodiversity, we used land as a of impacts on We the greenhouse-gas emissions from the of an We used by the Energy of the cost of electricity of different sources per unit of electricity delivered integrated over the of the production The cost and and waste and on the given to the in Fig. of the 3 scenarios might be considered the a scenario with low land use and carbon that is also the most and for biodiversity conservation. 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