A horizon scan of global conservation issues for 2014
Authors: William J. Sutherland, Rosalind Aveling, Thomas M. Brooks, Mick Clout, Lynn V. Dicks, Liz Fellman, Erica Fleishman, David W. Gibbons, Brandon Keim, Fiona Lickorish, Kathryn A. Monk, Diana Mortimer, Lloyd S. Peck, Jules Pretty, Johan Rockström, Jon Paul Rodríguez, Rebecca K. Smith, Mark D. Spalding, Femke H. Tonneijck, Andrew R. Watkinson
Journal: Trends in Ecology & Evolution (2013)

•This is the fifth in our annual series of horizon scans published in TREE.•We identify 15 issues that we considered insufficiently known by the conservation community.•These cover a wide range of issues. Four relate to climate change, two to invasives and two to disease spread.•This exercise has been influential in the past. This paper presents the output of our fifth annual horizon-scanning exercise, which aims to identify topics that increasingly may affect conservation of biological diversity, but have yet to be widely considered. A team of professional horizon scanners, researchers, practitioners, and a journalist identified 15 topics which were identified via an iterative, Delphi-like process. The 15 topics include a carbon market induced financial crash, rapid geographic expansion of macroalgal cultivation, genetic control of invasive species, probiotic therapy for amphibians, and an emerging snake fungal disease. This paper presents the output of our fifth annual horizon-scanning exercise, which aims to identify topics that increasingly may affect conservation of biological diversity, but have yet to be widely considered. A team of professional horizon scanners, researchers, practitioners, and a journalist identified 15 topics which were identified via an iterative, Delphi-like process. The 15 topics include a carbon market induced financial crash, rapid geographic expansion of macroalgal cultivation, genetic control of invasive species, probiotic therapy for amphibians, and an emerging snake fungal disease. Horizon scanning is the systematic search for, and examination of, potentially significant medium- to long-term threats and opportunities that are not well recognized within a particular field [1Sutherland W.J. Woodroof H.J. The need for environmental horizon scanning.Trends Ecol. Evol. 2009; 24: 523-527Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar]. The focus of this horizon scan is conservation, and it comprises the fifth in a series of annual assessments [2Sutherland W.J. et al.A horizon scan of global conservation issues for 2010.Trends Ecol. Evol. 2010; 25: 1-7Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar, 3Sutherland W.J. et al.A horizon scan of global conservation issues for 2011.Trends Ecol. Evol. 2011; 26: 10-16Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar, 4Sutherland W.J. et al.A horizon scan of global conservation issues for 2012.Trends Ecol. Evol. 2012; 27: 12-18Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar, 5Sutherland W.J. et al.A horizon scan of global conservation issues for 2013.Trends Ecol. Evol. 2013; 28: 16-22Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar]. Early identification of plausible future issues for conservation could reduce the probability of sudden confrontation with major social or environmental changes, such as the introduction of biofuels in the USA, Canada, and the European Union (EU) [1Sutherland W.J. Woodroof H.J. The need for environmental horizon scanning.Trends Ecol. Evol. 2009; 24: 523-527Abstract Full Text Full Text PDF PubMed Scopus (174) Google Scholar, 6Sutherland W.J. et al.Future novel threats and opportunities facing UK biodiversity identified by horizon scanning.J. Appl. Ecol. 2008; 45: 821-833Crossref Scopus (114) Google Scholar, 7Sutherland W.J. et al.The identification of priority opportunities for UK nature conservation policy.J. Appl. Ecol. 2010; 47: 955-965Crossref Scopus (58) Google Scholar]. Horizon scanning may also raise awareness and provide momentum to scientific, technological, and policy innovation. The use of horizon scanning in conservation is increasing. A parallel series of exercises has identified forthcoming changes in legislation that are likely to affect countries in the UK, the rest of the EU, and elsewhere [8Sutherland W.J. et al.What are the forthcoming legislative issues of interest to ecologists and conservationists in 2011?.Br. Ecol. Soc. Bull. 2011; 42: 26-31Google Scholar, 9Sutherland W.J. et al.What are the forthcoming legislative issues of interest to ecologists and conservationists in 2012?.Br. Ecol. Soc. Bull. 2012; 43: 12-19Google Scholar, 10Sutherland W.J. et al.What are the forthcoming legislative issues of interest to ecologists and conservationists in 2013?.Br. Ecol. Soc. Bull. 2013; 44: 38-43Google Scholar]. We are aware of planned horizon scans on environmental change in Antarctica, management of zoos and aquaria, and wetlands. High-priority questions for research and policy-making have also been identified for agriculture and natural resource management at national and international levels [11Sutherland W.J. et al.An assessment of the 100 questions of greatest importance to the conservation of global biological diversity.Conserv. Biol. 2009; 23: 557-567Crossref PubMed Scopus (413) Google Scholar, 12Pretty J. et al.The top 100 questions of importance to the future of global agriculture.Int. J. Agric. Sustain. 2010; 8: 219-236Crossref Scopus (356) Google Scholar, 13Dicks L.V. et al.What do we need to know to enhance the environmental sustainability of agricultural production? A prioritisation of knowledge needs for the UK food system.Sustainability. 2013; 5: 3095-3115Crossref Scopus (34) Google Scholar]. Such assessments of research and policy questions can be stimulated by horizon scans. The utility of horizon scans, individually or in aggregate, can be assessed in part by whether they succeeded in identifying topics that became major issues within a specified time frame, in our case years to decades. Several environmental topics identified by horizon scans published in TREE over the past 4 years, such as artificial life, synthetic meat [2Sutherland W.J. et al.A horizon scan of global conservation issues for 2010.Trends Ecol. Evol. 2010; 25: 1-7Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar], and hydraulic fracturing [3Sutherland W.J. et al.A horizon scan of global conservation issues for 2011.Trends Ecol. Evol. 2011; 26: 10-16Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar], have indeed moved from the horizon to the present, and are now widely discussed and better understood (see, for example, [14Fisk J.M. The right to know? State politics of fracking disclosure.Rev. Policy Res. 2013; 30: 345-365Crossref Scopus (43) Google Scholar]). The probability of a horizon issue becoming current may sometimes be low, but the issue nevertheless warrants identification if its effects could be substantial. Thus, it is not expected that all topics identified in a horizon scan will become prominent. An alternative metric of the value of horizon scanning could be a reduction in the proportion of emerging issues that were not identified. If forthcoming major issues are identified, then another measure of the importance of horizon scanning is the extent to which it encourages researchers to study emerging topics, and policy makers and practitioners to be vigilant and consider their responses should the issues be realized (e.g., [15Sutherland W.J. et al.Enhancing the value of horizon scanning through collaborative review.Oryx. 2012; 46: 368-374Crossref Scopus (18) Google Scholar]). A mechanism for increasing the utility of a horizon scan to serve this role is to use the scan to guide future strategies or funding. For example, the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), which held its first plenary meeting in 2011, seeks to lead the global scientific community in responding to major environmental changes. It has been suggested that IPBES use horizon scanning to develop its work program [16Vohland K. et al.How to ensure a credible and efficient IPBES?.Environ. Sci. Policy. 2011; 14: 1188-1194Crossref Scopus (41) Google Scholar], and Germany is already doing so to guide its input to the Platform. The outputs of horizon scans can directly inform policy-making. For example, during the continuing development and implementation of the Food Safety Modernization Act in the USA, federal regulators became aware that sterile farming could affect natural communities and ecosystems. The regulators were informed in part by identification of sterile farming in our 2012 horizon scan [4Sutherland W.J. et al.A horizon scan of global conservation issues for 2012.Trends Ecol. Evol. 2012; 27: 12-18Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar] and by subsequently published analyses of the potential environmental effects of sterile farming ([17Gennet S. et al.Farm practices for food safety: an emerging threat to floodplain and riparian ecosystems.Front. Ecol. Environ. 2013; 11: 236-242Crossref Scopus (34) Google Scholar]; personal communication Gennet 2013). Thus, arguably the greatest value of horizon scanning is stimulating action to prevent a plausible threat from being realized. The methods used in this horizon scan, described in [18Sutherland W.J. et al.Methods for collaboratively identifying research priorities and emerging issues in science and policy.Methods Ecol. Evol. 2011; 2: 238-247Crossref Scopus (251) Google Scholar], were the same as in our previous scans. The inclusive, transparent, and structured communication process we adopted is a modification of the Delphi technique, which was developed for systematic forecasting [19Rowe G. Wright G. The Delphi technique as a forecasting tool: issues and analysis.Int. J. Forecasting. 1999; 15: 353-375Crossref Scopus (1464) Google Scholar, 20Sutherland W.J. Predicting the ecological consequences of environmental change: a review of the methods.J. Appl. Ecol. 2006; 43: 599-616Crossref Scopus (217) Google Scholar]. The 20 core participants in the horizon scan (the authors) include professional horizon scanners and experts in disciplines relevant to conservation science who collectively are affiliated with organizations with diverse research, management, and communications mandates. Each participant, independently or in consultation with others, suggested two or more issues that they considered to be emerging, of global scope or relevance, and not widely known within the conservation community. At least 369 individuals actively contributed to the generation of ideas, of whom approximately 150 were reached through broad solicitation of the expert commissions of the International Union for Conservation of Nature. Short (approximately 200-word) descriptions of the resulting 81 issues were distributed to all core participants, who scored each issue from 1 (well known, or poorly known but unlikely to have substantial environmental effects) to 1000 (poorly known and likely to have substantial environmental effects). Scores were converted to ranks and the rank for each issue averaged across participants. The 35 issues with highest mean ranks, an additional four issues inadvertently omitted from the first round of scoring, and four issues that participants thought warranted further consideration were retained for further discussion. For each of these 43 issues, two participants who had not suggested the issue further researched its technical details and assessed its probability of becoming prominent. In September 2013, the core participants met in Cambridge, UK. Each issue was discussed in turn. The person who suggested the issue was not among the first three people to discuss it. Participants then independently and confidentially scored the issues again as described above. The 15 issues with the highest mean ranks are presented here. The order of presentation does not reflect mean rank, but related issues are placed together. There is an incompatibility between current stock market valuation of the fossil fuel industry, which is based on known and projected fuel reserves, and governmental commitments to prevent a rise in global average temperature of more than 2°C above pre-industrial levels [21Carbon Tracker Initiative Unburnable Carbon 2013: Wasted Capital and Stranded Assets. Carbon Tracker and Grantham Research Institute, 2013Google Scholar]. It has been suggested that the carbon budget from 2013 through 2050 should not exceed approximately 600–900 Gt CO2 for the probability of a >2°C temperature increase to remain ≤20% [21Carbon Tracker Initiative Unburnable Carbon 2013: Wasted Capital and Stranded Assets. Carbon Tracker and Grantham Research Institute, 2013Google Scholar, 22Meinshausen M. et al.Greenhouse-gas emission targets for limiting global warming to 2 degrees C.Nature. 2009; 458: 1158-1196Crossref PubMed Scopus (1910) Google Scholar, 23Meinshausen M. et al.The RCP greenhouse gas concentrations and their extensions from 1765 to 2300.Clim. Change. 2011; 109: 213-241Crossref Scopus (2534) Google Scholar]. By comparison, the carbon embedded in the known global coal, oil, and natural gas reserves amounts to 2860 Gt CO2. Reliable reserves held by companies listed on stock exchanges around the world already amount to 762 Gt CO2. Nonetheless, the industry invests approximately US$650 billion/yr in exploring new fossil-energy sources and in new extraction methods [21Carbon Tracker Initiative Unburnable Carbon 2013: Wasted Capital and Stranded Assets. Carbon Tracker and Grantham Research Institute, 2013Google Scholar]. For the 200 largest listed companies in the world, these reserves have an estimated market value of US$4 trillion. However, this market value may decline sharply if fossil fuels are not burned because regulations are developed to comply with international agreements on emission limits. If investors and regulators do not address these trade-offs, governments may be forced to choose between preventing further climate change (risking a financial crisis) or preventing a financial crisis (risking further climate change). In recent decades, over 10 million hectares of coastal and lowland peat swamp forest in Southeast Asia have been converted to drainage-based agriculture and plantations [24Page S. et al.Restoration ecology of lowland tropical peatlands in southeast Asia: current knowledge and future research directions.Ecosystems. 2009; 12: 888-905Crossref Scopus (210) Google Scholar], resulting in rapid peat oxidation [25Hooijer A. et al.Subsidence and carbon loss in drained tropical peatlands.Biogeosciences. 2012; 9: 1053-1071Crossref Scopus (363) Google Scholar, 26Couwenberg J. Hooijer A. Towards robust subsidence-based soil carbon emission factors for peat soils in south-east Asia, with special reference to oil palm plantations.Mires Peat. 2013; 12: 1-13Google Scholar]. Combined with compaction and shrinkage of peat, this conversion will lead to subsidence of almost all lowland peat in Indonesia and Malaysia by as much as 2.5 m within 50 years and 4 m within 100 years [26Couwenberg J. Hooijer A. Towards robust subsidence-based soil carbon emission factors for peat soils in south-east Asia, with special reference to oil palm plantations.Mires Peat. 2013; 12: 1-13Google Scholar]. In coastal areas and floodplains, subsidence could increase the probability of inundation well beyond projected effects of climate change, such as rising sea levels. In the Netherlands, long-term drainage of peat for agriculture has led to subsidence of extensive areas to 6–8 m below sea level. Costly systems, such as dykes, and pump-operated drainage systems have been necessary to avoid inundation of densely populated, economically productive areas [27Kabat P. et al.Dutch coasts in transition.Nat. Geosci. 2009; 2: 450-452Crossref Scopus (109) Google Scholar, 28Leifeld J. et al.Peatland subsidence and carbon loss from drained temperate fens.Soil Use Manage. 2011; 27: 170-176Crossref Scopus (81) Google Scholar]. The high intensity of rainfall in Southeast Asia means that mitigation measures applied in the temperate zone may not be effective and that extensive areas will be flooded. Yet, the focus of research, policy, and planning has been subsidence and associated flooding in urban areas [29Nicholls R.J. Cazenave A. Sea-level rise and its impact on coastal zones.Science. 2010; 328: 1517-1520Crossref PubMed Scopus (1670) Google Scholar]; peatland subsidence in rural areas has not been taken into account. Silicon-based solar photovoltaic cells are becoming a promising source of renewable energy as their installation costs decrease, potentially reducing the magnitude of climate change. However, construction requires rare conductive metals and indium tin oxide. Researchers have now built the first carbon solar cell, in which both the active layer and electrodes are carbon [30Ramuz M.P. et al.Evaluation of solution-processable carbon-based electrodes for all-carbon solar cells.ACS Nano. 2012; 6: 10384-10395Crossref PubMed Scopus (151) Google Scholar]. In a carbon solar cell, silver and indium tin oxide are replaced by graphene and single-walled carbon nanotubes, which are efficient conductors and light absorbers. Methods for producing carbon nanotubes, graphene, and fullerenes have also advanced substantially. Coating can be applied from solution, thus enabling the cells to be more flexible compared with rigid silicon cells. The thin-film cells that have been built with a carbon-based active layer are prototypes with relatively low efficiency (approximately 1% of solar energy is converted to electrical energy, compared with the 20% solar conversion efficiency of silicon-based solar cells; [31Shea M.J. Arnold M.S. 1% solar cells derived from ultrathin carbon nanotube photoabsorbing films.Appl. Phys. Lett. 2013; https://doi.org/10.1063/1.4811359Crossref Scopus (75) Google Scholar]). However, mass production could result in cheaper cells that could be installed on land (including on buildings) or in water, or worn by humans. The area necessary to operate carbon cells is smaller per unit energy than that of operating photovoltaic arrays [32Burke D.J. Lipomi D.J. Green chemistry for organic solar cells.Energy Environ. Sci. 2013; 6: 2053-2066Crossref Scopus (234) Google Scholar]. Carbon solar cells have the potential to reduce demands for other means of generating electricity that generate greater quantities of greenhouse gases, to provide electricity in regions where other sources of electric power are not available, and to power remote-tracking or data-recording devices. Algae have long been harvested for human consumption and, more recently, have been used in a range of food, biotechnology, cosmetics, and other industries. Research into industrial-scale macroalgal use as biofuel began during the 1970s [33McHugh D. A Guide to the Seaweed Industry. Food and Agriculture Organization of the United Nations, 2003Google Scholar], and there is now evidence that initial challenges of cost and efficiency are being overcome [34Suganya T. et al.Production of algal biodiesel from marine macroalgae Enteromorpha compressa by two step process: optimization and kinetic study.Bioresour. Technol. 2013; 128: 392-400Crossref PubMed Scopus (97) Google Scholar, 35Vanegas C.H. Bartlett J. Green energy from marine algae: biogas production and composition from the anaerobic digestion of Irish seaweed species.Environ. Technol. 2013; 34: 2277-2283Crossref PubMed Scopus (84) Google Scholar]. Potential marine-based biofuel capacity could be up to six times that of terrestrial biofuels [36Florentinus A. et al.Worldwide Potential Of Aquatic Biomass. Ecofys Bio Energy Group, for the Dutch Ministry of Environment, 2008Google Scholar] and both governments and industry are now investing in trials and modest expansion in, for example, Australia, Denmark, Ireland, Norway, Portugal, and the UK (e.g., http://www.biomara.org and http://www.seaweedenergysolutions.com). Opportunities for expansion of macroalgal production in developing countries could be considerable [37Ecofys Algal-based Biofuels: A Review of Challenges and Opportunities for Developing Countries. Ecofys, Global Bioenergy Partnership, Food and Agriculture Organization of the United Nations, 2009Google Scholar]. Unlike many biofuels, macroalgae do not compete for agricultural space or for freshwater. However, macroalgal cultivation still requires considerable space in often intensively used coastal waters, and may suppress benthic communities, such as seagrasses. One future scenario developed by the UK Government included over 470 000 ha of macroalgal culture by 2050 [38Department of Energy and Climate Change 2050 Pathways Analysis. Department of Energy and Climate Change, London, UK, 2010Google Scholar]. Although macroalgal cultivation may create competition with other sectors, there could be synergies with both offshore production of renewable energy and fish cultivation [39Roberts T. Upham P. Prospects for the use of macro-algae for fuel in Ireland and the UK: an overview of marine management issues.Mar. Policy. 2012; 36: 1047-1053Crossref Scopus (31) Google Scholar]. The ecological effects of extensive production are as yet unknown, but could change the structure, composition, and function of marine environments through shading, smothering, and the alteration of nutrient regimes and trophic pathways. The steady increase in the concentration of greenhouse gases has resulted in temperature increases of approximately 0.8°C at the surface of the Earth over the past 150 years. However, the rate of surface temperature increase has slowed over the past decade. The change in rate could be a result of typical climate variability, but there is some evidence that the heat has been redistributed and much of the warming has occurred in the ocean at depths below 700 m, rather than at the surface [40Balmaseda M.A. et al.Distinctive climate signals in reanalysis of global ocean heat content.Geophys. Res. Lett. 2013; 40: 1754-1759Crossref Scopus (407) Google Scholar, 41Held I.M. Climate science: the cause of the pause.Nature. 2013; 501: 318-319Crossref PubMed Scopus (40) Google Scholar, 42Rosenthal Y. et al.Pacific ocean heat content during the past 10,000 years.Science. 2013; 342: 617-621Crossref PubMed Scopus (68) Google Scholar]. Correction of the data for changes in measurement methods does not remove the temporal trend. The redistribution, which is thought to result from changes in surface winds over the past decade, raises uncertainties about the capacity of the deep ocean to absorb heat energy, potential feedbacks on the melting of polar ice sheet due to upwelling of warmer ocean water, and the effect of redistribution on ocean currents. Redistribution may also reduce the projected magnitude of responses of organisms that live on land or near the sea surface to increases in global temperature. Furthermore, the likely effects of increases in ocean temperature on deep sea and other marine species are unknown. Policy makers could erroneously interpret the reduced rate of surface temperature increase as a lower climate forcing from greenhouse gas emissions rather than a reflection of the complex interactions of natural variability and global resilience to greenhouse gas emissions. This misinterpretation may lead to calls to slow policy initiatives aimed at reducing greenhouse gas emissions. As new satellites and remote sensors are deployed, the quantity and quality of data available at low to no charge will increase dramatically. Simultaneously, free or inexpensive data from established aerial imagery and satellite systems will enable temporally consistent monitoring of land cover. The moderate resolution imaging spectroradiometer (MODIS) and Landsat acquire global images every 7–16 days and privately operated satellites, such as the Disaster Monitoring Constellation 3 (Surrey Satellite Technology Ltd), due to be launched in 2014, have the potential for daily acquisition of images over smaller areas. This means that it is now theoretically possible to monitor land cover in near real-time. However, data processing is still labor intensive and image quality affects interpretation. Some land-cover types, such as tropical rain forest, urban, and certain crops, are easy to monitor (e.g., [43Pittman K. et al.Estimating global cropland extent with multi-year MODIS data.Remote Sens. 2010; 2: 1844-1863Crossref Scopus (211) Google Scholar, 44Townshend J.R. et al.Global characterization and monitoring of forestcover using Landsat data: opportunities and challenges.Int. J. Digit. Earth. 2012; 5: 373-397Crossref Scopus (238) Google Scholar]) whereas others, such as native grasslands and aquatic types, are more difficult. Frequent, fine-resolution monitoring is currently most feasible at relatively small spatial extents (e.g., tens of km) and for a subset of land-cover types, in particular those with trees. The ability to monitor land-use change at high temporal frequency over larger extents could inform management of international efforts to mitigate climate change, or certification of sustainable farmed food or fuel products in global supply chains. Anticipated advances, such as automated image processing, the differentiation of nonforest land-cover types, and the identification of features at finer resolutions, will make this technology increasingly useful. Organized crime syndicates are driving a dramatic acceleration in the loss of elephants and rhinoceroses across Africa and Asia, undermining decades of concerted conservation action. The number of forest elephants (Loxodonta cyclotis) in central Africa declined by 62% between 2002 and 2011, and the geographical range of the taxon decreased by 30% [45Maisels F. et al.Devastating decline of forest elephants in Central Africa.PLoS ONE. 2013; https://doi.org/10.1371/journal.pone.0059469Crossref PubMed Scopus (238) Google Scholar]. High human population density, intensive and/or illegal hunting, absence of law enforcement, poor governance, and proximity to expanding infrastructure are fuelling this decline [45Maisels F. et al.Devastating decline of forest elephants in Central Africa.PLoS ONE. 2013; https://doi.org/10.1371/journal.pone.0059469Crossref PubMed Scopus (238) Google Scholar]. Ivory poaching has increased dramatically over the past decade [46CITES Interpretation and Implementation of the Convention: Species Trade and Conservation: Elephants. Monitoring of Illegal Trade in Ivory and Other Elephant Specimens. Report of the Secretariat. Convention On International Trade In Endangered Species of Wild Fauna and Flora, 2012Google Scholar], largely due to the increasing price and demand for ivory in China [47Vigne L. Martin E. Consumption of elephant and mammoth ivory increases in southern China.Pachyderm. 2011; 49: 79-89Google Scholar, 48Wittemyer G. et al.Rising ivory prices threaten elephants.Nature. 2011; 476: 282-283Crossref PubMed Scopus (22) Google Scholar]. Even in well-protected reserves, threats to the species have escalated [48Wittemyer G. et al.Rising ivory prices threaten elephants.Nature. 2011; 476: 282-283Crossref PubMed Scopus (22) Google Scholar]. The International Union for Conservation of Nature (IUCN) Species Survival Commission estimated that, at the start of 2013, there were 20 405 white rhinoceros (Ceratotherium simum) and 5055 black rhinoceros (Diceros bicornis) across Africa; by September, 613 rhinoceros had been poached for their horn in South Africa alone, many more than in 2011 or 2012. The retail price of rhinoceros horn in user countries still exceeds that of gold [49Milliken T. Shaw J. The South Africa – Vietnam Rhino Horn Trade Nexus: A Deadly Combination of Institutional Lapses, Corrupt Wildlife Industry Professionals and Asian Crime Syndicates. TRAFFIC, 2012Google Scholar]. With growing wealth in Asia and as the species become scarcer, their value might increase even further and escalate speculation for illegally traded commodities, such as elephant ivory and rhinoceros horn. There may soon be a step change in the potential spatial extent of eradications of non-native invasive mammals on islands as expertise and techniques improve. Such methods include new toxins (e.g., para-aminopropiophenone), and the use of global positioning systems to deliver baits aerially [50Veitch C.R. et al.Island Invasives: Eradication and Management. IUCN and CBB, 2011Google Scholar] (http://eradicationsdb.fos.auckland.ac.nz/). Recent or current extensive programs that have been successful include the eradication of rabbits (Oryctolagus cuniculus), black rats (Rattus rattus), and feral domestic cats (Felis catus) from Macquarie Island (12 800 ha), and goats (Capra aegagrus hircus) from Aldabra (15 400 ha) and Isabela (463 000 ha). The eradication of reindeer (Rangifer tarandus), brown rats (Rattus norvegicus), and house mice (Mus musculus) from South Georgia (360 000 ha) is underway. There are also recent examples of unsuccessful eradication campaigns, such as Pacific rats (Rattus exulans) from Henderson Island (4300 ha; http://eradicationsdb.fos.auckland.ac.nz/). The potential of new toxins and tools (e.g., lures, rechargeable traps, and bait dispensers) to attract and eradicate non-native mammals at low densities is being assessed. Given such advances, it has been proposed to eradicate all non-native invasive mammalian predators [rats, stoats (Mustela erminea), and possums (Trichosurus vulpecula)] from the entire New Zealand archipelago, starting with Rakiura-Stewart Island (>174 000 ha) [51Bell P. Bramley A. Eliminating Predators from Stewart Island: A Scoping Report. Department of Conservation, Auckland, New Zealand, 2013Google Scholar]. A more controversial but highly publicized campaign ('Cats to Go'; http://garethsworld.com/catstogo) encourages New Zealand citizens to protect native birds by ceasing to keep domestic cats as pets. Spatially extensive eradications increase the probability of conserving native species, but the risks of failure and public opposition may also grow as the extent of eradications increases and encompasses places with large human populations (e.g., [