We maintain that humanity’s grand challenge is solving the intertwined problems of human population growth and overconsumption, climate change, pollution, ecosystem destruction, disease spillovers, and extinction, in order to avoid environmental tipping points that would make human life more difficult and would irrevocably damage planetary life support systems. These are not future issues: for example, detrimental impacts of climate change (increased wildfires and extreme weather, sea-level rise, ocean acidification), pollution (contaminated drinking water in many parts of the world), rapid population growth in some areas (contributing to poverty, war, and increasingly frequent migration) and overconsumption in others (a main driver of overexploitation of resources and greenhouse gas emissions), and new disease outbreaks (Ebola, Zika virus) already are apparent today, and if trends of the past half century continue, even more damaging, long-lasting impacts would be locked in within three decades. Solving these problems will require some scientific and technological breakthroughs, but that will not be enough. Even more critical will be effective collaboration of environmental and physical scientists with social scientists and those in the humanities, active exchange of information among practitioners in academics, politics, religion, and business and other stakeholders, and clear communication of relevant issues and solutions to the general public. This special feature offers examples of how researchers are addressing this grand challenge through the process of discovering new knowledge and relevant tools, transferring insights across disciplinary boundaries, and establishing critical dialogues with those outside academia to help effect positive global change.
Until recently, the planet was so big compared to humanity’s impacts that Earth’s resources seemed limitless. We now know that is not the case (Barnosky et al., 2014; Barnosky and Hadly, 2015; Brown et al., 2011; Ehrlich and Ehrlich, 2013; GFN, 2013; Rockström et al., 2009). The human population has nearly tripled in just one human lifetime, and, at 7.3 billion people and counting, is still growing rapidly (Ehrlich and Ehrlich, 2013; PRB, 2015; UNDESA, 2013a, 2013b), with almost a quarter of a million more people added every day: the equivalent of a new Hong Kong every month and more than a new Pakistan every two years. Provisioning the food, housing, water, and other goods and services desired by these ever-growing numbers of people has transformed more than 50% of the planet into human constructs like farms, pastures, cities, towns, roads, and dams (Barnosky et al., 2012; Foley, 2011; Foley et al., 2011; Hooke et al., 2012). Virtually all of the world’s most productive land is already being used to grow food (Ehrlich and Ehrlich, 2013; Foley et al., 2011), and more than 60% of the world’s big rivers have been dammed (Hoekstra et al., 2010). Humans now co-opt more than one third of the energy that photosynthesis provides for all the species in the world to share, measured as Net Primary Productivity (NPP), mostly for food and biofuel production (Grosso et al., 2008; Haberl et al., 2007; Running, 2012; Smith et al., 2012; Vitousek et al., 1986, 1997). Even so, about one in nine people in the world go hungry each day, about a third are malnourished, and more than one in seven get by on a bare minimum of water (Barnosky et al., 2014; FAO, 2012, 2015; Shah, 2011, 2013; WHO, 2013). In some regions these problems reflect lack adequate resources with respect to local population sizes—for example, a shortage of arable land, adequate rainfall, and NPP in the Sahel (Abdi et al., 2014). But, on a global scale, the obstacle to many people obtaining adequate life-support resources also arises from political, economic, and social factors (Gower et al., 2012), including large inequalities in economic opportunities and land tenure rights, or poor infrastructure—as is the case for food production, for example. Although global crop yields are sufficient to feed the world (so far), distribution mechanisms are inadequate to transport it where it is needed (FAO, 2015; Foley et al., 2011).
Producing what billions of people need to survive requires energy in amounts that now far exceed what terrestrial photosynthesis can provide (Barnosky, 2008, 2014; Smil, 2011), a shortfall that will continue to grow with human population growth, and will be exacerbated even further with increasing levels of production and consumption of goods. Since the Industrial Revolution, we have produced most of the extra energy the global society needs by burning massive amounts of fossil fuels—in effect, prehistoric net primary productivity. Relying on fossil fuels to augment the global energy budget has input CO2 (and other greenhouse gases) into the atmosphere at a pace that is 200 times faster than what was normal for Earth’s pre-industrial carbon cycle (Archer et al., 2009; Berner, 2003; DePaolo et al., 2008). The richest one billion of us—only 15% of the human population—consume half of the energy produced by fossil fuels (Ramanathan et al., 2015), and consequently have been responsible for 60% of the CO2 problem. In contrast, the poorest 3 billion people account for only about 5% of CO2 emissions (Ramanathan et al., 2015). Because of greenhouse gas emissions, the net effect of relying on fossil fuels is that we are now changing climate faster than people have ever experienced since our ancestors became Homo sapiens (Blois and Hadly, 2009; Diffenbaugh and Field, 2013; IPCC, 2007, 2013). Already the changing climate is manifesting as more frequent floods, wildfires and heat waves that kill thousands of people annually; rising sea levels that displace whole communities and cost hundreds of billions of dollars for coastal infrastructure building and repair; and as increasingly acid oceans, which in some places are becoming so acidic that oyster and scallop fisheries are beginning to collapse (Barnosky and Hadly, 2015; Barton et al., 2012; Gazeau et al., 2011; Liu et al., 2012; Miller et al., 2009). Air pollution from burning fossil fuels also has long been recognized as a growing problem, to the extent that more than six million people die from it each year (Lim et al., 2012; WHO, 2011).
The gases and particulates from burning fossil fuels are but one example of globally distributed pollutants. By-products of the fertilizers, herbicides and pesticides we presently rely on to grow food for the world, the pharmaceuticals we use, the chemicals utilized in manufacturing and mining, and the trash we discard have contaminated even the most remote environments of the world (Diaz and Rosenberg, 2008; Hayes et al., 2003; Lim et al., 2012; Newbold et al., 2009; Qiu, 2013; Staff, 2012). Many of these toxins have recently been shown to mimic hormones important in the metabolism of people and other animals, and may be much more dangerous in small rather than large concentrations – reversing the old slogan that “the dose makes the poison.” Whales and polar bears harbor such toxins in their tissues; arctic lakes far from any human settlements exhibit elevated nitrogen levels; Texas-sized trash gyres swirl in the middle of the oceans; and both macro and microscopic plastic debris has become a ubiquitous constituent of the marine sediments (Andrady, 2011; Barnes et al., 2009, 2010; Cole et al., 2011; Fendall and Sewell, 2009; Ng and Obbard, 2006; Ryan et al., 2009; Zarfl et al., 2011; Zarfl and Matthies, 2010).
Increasing encroachment of humans into previously little-touched ecosystems is disrupting non-human communities and leading to more frequent and severe ‘spillovers’ of disease (Barnosky and Hadly, 2015; Quammen, 2012). Our limited knowledge of the reservoirs and vectors of these potential killers means that we can only guess from where and when they will emerge. Climatic change is further increasing the odds that novel diseases will crop up in humans and the plants and animals on which we depend: most of the world’s diseases are tropical in origin, and as we build roads and destroy habitats there, we disrupt the native systems leading to an increased probability of exposure risk to us. Spillover from humans to animals is increasing as well—many of our wild, and sometimes migratory, animals are afflicted with antibiotic resistant forms of bacteria such as MRSA.
All of these human impacts add up to losses or serious degradation of more than half of the habitats (Hooke et al., 2012) that once supported many non-human species, and along with poaching, overfishing, and generally exploiting nature for short-term profit, have accelerated the extinction rate of wild animals and plants to levels not seen since the dinosaurs died out (Barnosky, 2014; Barnosky et al., 2011; Ceballos et al., 2015; Dirzo and Raven, 2003; GBO3, 2010; Pimm et al., 2006, 2014; Urban, 2015). The resulting loss of benefits to humankind already includes reduction in direct ecosystem services such as water filtration, pollination of crops, control of pests, food production, and emotional fulfillment, and indirect impacts like the spread of pathogens ranging from Lyme disease to Ebola (Barnosky and Hadly, 2015; Cardinale et al., 2012; Daily et al., 2000; Ehrlich et al., 2012; Foley et al., 2005, 2011; Jackson, 2008; McCauley et al., 2015; Tercek and Adams, 2013; Tyrrell, 2011; Vitousek et al., 1986, 1997; Young et al., 2014). Table 1 highlights the six crucial environmental problems on which this Special Feature focuses.
Table 1. Environmental issues of key concerna
|Climate disruption||More, faster climate change has occurred than since humans first became a species.|
|Extinctions||Not since the dinosaurs went extinct have so many species and populations died out so fast, both on land and in the oceans.|
|Wholesale loss of diverse ecosystems||We have plowed, paved, or otherwise transformed more than 50% of Earth’s ice-free land, and no place on land or in the sea is free of our direct or indirect influences.|
|Pollution||Environmental contaminants in the air, water and land are at record levels and increasing, seriously harming people and wildlife in unforeseen ways.|
|Human population growth and consumption patterns||More than seven billion people alive today will likely grow to 9.5 billion by 2050, and the pressures of heavy material consumption among the middle class and wealthy may well intensify.|
|Disease||More contact through destruction of intact ecosystems combined with dramatically changed environments are leading to increases in the rates and types of sicknesses that harm humans, other animals and plants.|
A large body of science now documents that if these problems continue to grow as they have over the past half-century, the result will be substantial harm to human wellbeing by 2050 (Scientific Consensus on Maintaining Humanity’s Life Support Systems in the 21st Century), (Barnosky et al., 2012, 2014; Brown et al., 2011; Ehrlich and Ehrlich, 2013), even the possible collapse of civilization as we know it.
The next four decades
At the root of all of the threats listed above are the numbers of people in the world and the ecological footprint of each (GFN, 2013; Rockström et al., 2009; WWF, 2012), especially the excessively large per capita ecological footprints in high income countries (WWF et al., 2014). With respect to population growth, the best-case scenarios indicate that by 2050, the planet will have to support at least two billion to three billion people more than it does today (PRB, 2015; UNDESA, 2013a, 2013b). In order to feed that many more people, business-as-usual food production, distribution, and wastage would require converting even more of Earth’s lands to agriculture, and overfishing more of the sea—but, there simply isn’t enough productive land left to accomplish that, or enough of the species we presently like to eat left in the ocean (Ehrlich and Ehrlich, 2013; Foley, 2011; Foley et al., 2011; Jackson, 2008; Jackson et al., 2001; McCauley et al., 2015). Under business-as-usual burning of fossil fuels, the increased food production would have to take place under climate stresses that agriculture and aquaculture have not yet witnessed (Challinor et al., 2014; Lobell et al., 2008; Moore and Lobell, 2014; Ray et al., 2013; Trnka et al., 2014; West et al., 2014; White et al., 2013). Our present commensal animal population (cows, sheep, etc.) is more than three times the biomass than humans account for, and all of those animals require food and water, not to mention waste management (Barnosky, 2008; Barnosky and Hadly, 2015; Smil, 2011). Present emissions trajectories would, by mid-century, heat the planet to a level that humans and most other vertebrate species have never experienced (Blois and Hadly, 2009), inhibiting not only food production, but also greatly multiplying other climate-change problems already apparent (IPCC, 2013, 2014; IPCC-SREX, 2012; White et al., 2013), including exacerbating global conflict and national security concerns (CNA, 2007, 2014; Steinbruner et al., 2012). Indeed, if the present climate-change trajectory continued to 2100, Earth would be hotter than it has been in at least 14 million years, and large regions would be too hot to support human life outdoors (Sherwood and Huber, 2010). Even now, heat waves kill thousands of people increasingly frequently. Using presently accepted norms of manufacturing the goods and services to maintain present rates of consumption—not even accounting for the desirability of raising standards of living for billions of poor people today—would dramatically increase what already are dangerous levels of environmental contamination worldwide, and deplete critical natural resources we depend upon today—including water (Barnosky and Hadly, 2015). And, should present rates of extinction continue, in as little as two human lifetimes, Earth would lose three out of every four familiar species forever—a so-called Sixth Mass Extinction that is now beginning, an interruption of life so rare that it has occurred only five times since complex animals evolved half a billion years ago (Barnosky, 2014; Barnosky et al., 2011; Ceballos et al., 2015; Pimm et al., 2014). Already biodiversity is under such pressure that wildlife has suffered gigantic losses: more than half of all the Earth’s vertebrate animals have been killed within four decades – a “defaunation” unprecedented in the history of humanity (WWF et al., 2014).
In reality, of course, the six problems listed in Table 1 are intertwined and feed back on one another (Barnosky et al., 2014; Barnosky and Hadly, 2015; Barnosky et al., 2012; Rockström et al., 2009; Steffen et al., 2011). As they act in concert, the risks of detrimental outcomes become greatly magnified.
The grand challenge
The grand challenge for science and society, then, is how to solve the intertwined problems of human population growth and overconsumption, climate change, pollution, ecosystem destruction, disease spillovers, and extinction, in order to avoid environmental tipping points that would make human life infinitely more difficult. Researchers in many disciplines have long recognized this challenge, and discussed it widely, especially in academic circles, for more than four decades, both from the perspective of the natural sciences (Table 2) and the social sciences (Leach et al., 2013; Raworth, 2012). However, understanding the problems stops short of fixing them, if the inter-related facets of seemingly distinct issues are not recognized, and if few outside the scientific community realize or accept that the problems are serious and that solutions are at hand. Therefore, a huge challenge within academia is working across traditional disciplinary boundaries to connect different pieces of the solutions puzzle that are emerging from practitioners spread across many different specialties (Cash et al., 2003; Ramanathan et al., 2015). And, an even bigger challenge is to take the knowledge developed within academia and collaborate closely with stakeholders in ways that elicit significant action (Ehrlich et al., 2012; Gibbons, 1999; Klenk et al., 2015). This is especially important, since guiding the planet for the future will likely require some fundamental changes—not just in human economic and governance systems—but also in societal values. Engagement with religious leaders, local communities and businesses, subnational groups and the military and security sectors of society, recently starting to burgeon, are critically important to further these necessary conversations and impel action (CNA, 2007, 2014; PAS and PASS, 2014; Ramanathan et al., 2015; Under2MOU, 2015; Vatican, 2015; WBSCD, 2013a, 2013b).
Table 2. Broad-brush solutions to key environmental problemsa
|Climate Disruption||Reduce effects of climate disruption by decreasing greenhouse gas emissions, and by implementing adaptation strategies to deal with the consequences of climate change already underway. Viable approaches include accelerating development and deployment of carbon neutral energy technologies to replace fossil fuels; making buildings, transportation, manufacturing systems, and settlement patterns more energy-efficient; and conserving forests and regulating land conversion to maximize carbon sequestration. Adapting to the inevitable effects of climate change will be crucial for coastal areas threatened by sea level rise; ensuring adequate water supplies to many major population centers; maintaining agricultural productivity and for managing biodiversity and ecosystem reserves.|
|Extinctions||Slow the very high extinction rates that are leading to a global loss of biodiversity. Viable approaches include assigning economic valuation to the ways natural ecosystems contribute to human well-being and managing all ecosystems, both in human-dominated regions and in regions far from direct human influence, to sustain and enhance biodiversity and ecosystem services. It will be critical to develop cross-jurisdictional cooperation to recognize and mitigate the interactions of global pressures (for example, climate change, ocean acidification) and local pressures (land transformation, overfishing, poaching endangered species, etc.).|
|Ecosystem Transformation||Minimize transformation of Earth’s remaining natural ecosystems into farms, suburbs, and other human constructs. Viable agricultural approaches include increasing efficiency in existing food-producing areas; improving food-distribution systems; and decreasing waste. Viable development approaches include enhancing urban landscapes to accommodate growth rather than encouraging suburban sprawl; siting infrastructure to minimize impacts on natural ecosystems; and investing in vital ‘green infrastructure,’ such as through restoring wetlands, oyster reefs, and forests to secure water quality, flood control, and boost access to recreational benefits.|
|Pollution||Curb the manufacture and release of toxic substances into the environment. Viable approaches include using current science about the molecular mechanisms of toxicity and applying the precautionary principle (verification of no harmful effects) to guide regulation of existing chemicals and design of new ones. We have the knowledge and ability to develop a new generation of materials that are inherently far safer than what is available today.|
|Population Growth and Consumption||Bring world population growth to an end as early as possible and begin a gradual decline. An achievable target is no more than 8.5 billion people by 2050 and a peak population size of no more than 9 billion, which through natural demographic processes can decrease to less than 7 billion by 2100. Viable approaches include ensuring that everyone has access to education, economic opportunities, and health care, including family planning services, with a special focus on women’s rights. Decrease per-capita resource use, particularly in developed countries. Viable approaches include improving efficiency in production, acquisition, trade, and use of goods and promoting environmentally friendly changes in consumer behavior.|
|Disease||Limit road-building and penetration of intact tropical forests. Designate remaining tropical regions for limited dissection and extraction of resources. Better on-the-ground monitoring of the areas under resource extraction will help us ascertain where and when outbreaks are likely to occur. Since most global disease is a subset of tropical diseases, our focus should be on those areas in particular, but even temperate regions require vigilance—chronic wasting disease, for example, threatens wild and farmed animals alike in North America. Anticipate global disease outbreaks and increase collaboration for containment and treatment. Our experience with Ebola taught the world that we are woefully underprepared to coordinate and contain even very infectious diseases. Increased communication and collaboration here is critical.|
In this Special Feature, we offer six examples of how researchers are addressing these challenges through the process of discovering new knowledge and relevant tools within academia, and sharing knowledge and learning from stakeholders outside the Ivory Tower. The examples take the form of three articles and three web sites. The Special Feature arose from the symposium “Avoiding Collapse: Human Impacts on the Biosphere,” at the 2015 American Association for the Advancement of Science Annual Meeting in San Jose, California, and the three articles are extensions of presentations that were conveyed there. To illustrate the key role of science and industry in developing new information technology that will be critical in identifying and responding to global change, Dawn Wright shares insights on digital resilience, and what that means for policy-making and conservation. Tyrone Hayes and Martin Hansen highlight the intersections between food production, environmental contamination, and some social and economic obstacles that stand in the way of sustainable agriculture. And Vice Admiral Lee Gun (Ret.) bridges the divide between science and society by assessing the national security implications of climate change—and expresses a view increasingly echoed at the highest levels of the national security community.
The three websites were constructed specifically to bridge the science-society divide. The Millennium Alliance for Humanity and the Biosphere (http://mahb.stanford.edu) was founded to connect scientists, humanists, activists and civil society in order to foster positive global change. The Consensus For Action website (http://consensusforaction.stanford.edu) is an outgrowth of the Scientific Consensus on Maintaining Humanity’s Life Support Systems in the 21st Century: Information for Policy Makers (Barnosky et al., 2014) a document which has been circulated to political leaders worldwide and used in discussions leading to international climate agreements. The website provides a venue for policy makers to quickly digest why it is essential to immediately address the issues of climate change, extinctions, ecosystem loss, pollution, and population overgrowth; for scientists to indicate to policy makers throughout the world the importance of dealing with those key environmental issues; and for the general public to voice their support to policy makers for taking action. The third website (Figure 1), “Mapping the Impacts of Global Change: Stories of Our Changing Environment as Told By U.S. Citizens” (http://www.mappingglobalchange.org), was developed to provide rapid and locally relevant information to everyone, from the general public to political leaders, about how these threats to humanity’s life support systems play out, and resulted from dialogues between university students and faculty, policy makers at the state through national levels, and everyday citizens (Mychajliw et al., 2015).
These six examples illustrate that there is no one-size-fits all approach for researchers to address today’s grand environmental challenges, but two common themes emerge. The first is that it is no longer enough to simply do the science and publish an academic paper; that is a necessary first step, but moves only halfway towards the goal of guiding the planet towards a future that is sustainable for both human civilization and the biosphere. To implement knowledge that arises from basic research, it is necessary to establish dialogues and collaborations that transcend narrow academic specialties, and bridge between academia, industry, the policy community and society in general. The second theme is that now is the time to rise to these scientific and communication challenges. The trajectories of population overgrowth, climate change, ecosystem loss, extinctions, disease, and environmental contamination have been rapidly accelerating over the past half-century. If not arrested within the next decade, their momentum may prevent us from stopping them short of disaster.
- Abdi AM, Seaquist J, Tenenbaum DE, Eklundh L, Ardö J2014. Environ Res Lett 9
- Andrady AL2011. Mar Pollut Bull 62(8): 1596–1605
- Archer D, Eby M, Brovkin V, Ridgwell A, Cao L, et al.2009. Annu Rev Earth Planet Sci 37: 117–134
- Barnes DKA, Galgani F, Thompson RC, Barlaz M2009. Philos Trans R Soc B 364(1526): 1985–1998
- Barnes DKA, Walters A, Gonçalves L2010. Mar Environ Res 70(2): 250–252
- Barnosky AD2008. P Natl Acad Sci USA 105(1): 11543–11548
Dodging Extinction: Power, Food, Money, and the Future of Life on EarthBarnosky AD2014. Berkeley, California: University of California Press
Introducing the Scientific Consensus on Maintaining Humanity's Life Support Systems in the 21st Century: Information for Policy MakersBarnosky AD, Brown JH, Daily GC, Dirzo R, Ehrlich AH, et al.2014. The Anthropocene Review 1: 78–109
End Game: Tipping Point for Planet Earth?Barnosky AD, Hadly EA2015. London: HarperCollins UK
- Barnosky AD, Hadly EA, Bascompte J, Berlow EL, Brown JH, et al.2012. Nature 486: 52–56
- Barnosky AD, Matzke N, Tomiya S, Wogan GOU, Swartz B, et al.2011. Nature 471: 51–57
The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: Implications for near-term ocean acidification effectsBarton A, Hales B, Waldbusser GG, Langdon C, Feely RA2012. Limnol Oceanogr 57(3): 698–710
- Berner RA2003. Nature 426: 323–326
- Blois JL, Hadly EA2009. Annu Rev Earth Planet Sci 37: 8.1–8.28
- Brown JH, Burnside WR, Davidson AD, Delong JR, Dunn WC, et al.2011. BioScience 61(1): 19–26
- Cardinale BJ, Duffy JE, Gonzalez A, Hooper DU, Perrings C, et al.2012. Nature 486: 59–67
- Cash DW, Clark WC, Alcock F, Dickson NM, Eckley N, et al.2003. P Natl Acad Sci 100(14): 8086–8091
- Ceballos G, Ehrlich PR, Barnosky AD, García A, Pringle RM, et al.2015. Sci Adv 1(5): e1400253
- Challinor AJ, Watson J, Lobell DB, Howden SM, Smith DR, et al.2014. Nat Clim Change 4: 287–291
- CNA2007. Alexandria, Virginia: CNA Corporation
- CNA2014. Alexandria, Virginia: CNA Corporation
- Cole M, Lindeque P, Halsband C, Galloway TS2011. Mar Pollut Bull 62(12): 2588–2597
- Daily GC, Söderqvist T, Aniyar S, Arrow K, Dasgupta P, et al.2000. Science 289: 395–396
Origin and evolution of Earth: Research questions for a changing planetDePaolo DJ, Cerling TE, Hemming SR, Knoll AH, Richter FM, et al.2008. The National Academies Press
- Diaz RJ, Rosenberg R2008. Science 321: 926–929
- Diffenbaugh NS, Field CB2013. Science 341(6145): 486–492
- Dirzo R, Raven PH2003. Annu Rev Environ Resour 28: 137–167
- Ehrlich PR, Ehrlich AH2013. Proc R Soc B 280
- Ehrlich PR, Kareiva PM, Daily GC2012. Nature 486: 68–73
The State of Food Insecurity in the World 2012FAO2012. Rome: Food and Agriculture Organization of the United Nations
The state of food insecurity in the world, Meeting the 2015 international hunger targets: taking stock of uneven progressFAO 2015. In Rome: Food and Agriculture Organization of the United Nations
- Fendall LS, Sewell MA2009. Mar Pollut Bull 58(8): 1225–1228
- Foley JA2011. Sci Am 2011: 60–65 November.
- Foley JA, DeFries R, Asner GP, Barford C, Bonan G, et al.2005. Science 309: 570–574
- Foley JA, Ramankutty N, Brauman KA, Cassidy ES, Gerber JS, et al.2011. Nature 478: 337–342
Effect of carbonate chemistry alteration on the early embryonic development of the Pacific Oyster (Crassostrea gigas)Gazeau F, Gattuso JP, Greaves M, Elderfield H, Peene J, et al.2011. PLoS ONE 6(8): e23010
Global Biodiversity Outlook 3GBO32010. Montréal: Secretariat of the Convention on Biological Diversity
Global Footprint Network, Advancing the Science of SustainabilityGFN2013. Accessed March 29, 2014.
Sciences new social contract with societyGibbons M1999. Nature 402: 11–17
Left behind by the G20? How inequality and environmental degradation threaten to exclude poor people from the benefits of economic growthGower R, Pearce C, Raworth K2012. Oxfam Briefing Paper 157(19 January 2012): 1–46
Global potential net primary production predicted from vegetation class, precipitation, and temperatureGrosso SD, Parton W, Stohlgren T, Zheng D, Bachelet D, et al.2008. Ecology 89: 2117–2126
Quantifying and mapping the human appropriation of net primary production in Earth’s terrestrial ecosystemsHaberl H, Erb K-H, Krausmann F, Gaube V, Bondeau A, et al.2007. P Natl Acad Sci 104: 12942–12947
Atrazine-Induced Hermaphroditism at 0.1 ppb in American Leopard Frogs (Rana pipiens): Laboratory and Field EvidenceHayes T, Haston K, Tsui M, Hoang A, Haeffele C, et al.2003. Environ Health Perspect 111(4): 568–575
The Atlas of Global ConservationHoekstra JM, Molnar JL, Jennings M, Revenga C, Spaulding MD, et al.2010. Berkeley: University of California Press
- Hooke RL, Martín-Duque JF, Pedraza J2012. GSA Today 22(12): 1–10
Intergovernmental Panel on Climate Change: Fourth Assessment Report (AR4)IPCC2007.
- IPCC 2013. In Climate Change 2013: The Physical Science Basis Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press
- IPCC 2014. In Climate Change 2014, Mitigation of Climate Change Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press
Special Report of the Intergovernmental Panel on Climate ChangeIPCC-SREX 2012. In Field CB, Barros V, Stocker TF, Dahe Q, Dokken DJ, et al., eds., Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. New York: Cambridge University Press: pp 1–594.
- Jackson JBC2008. P Natl Acad Sci 105(Supplement 1): 11458–11465
- Jackson JBC, Kirby MX, Berger WH, Bjorndal KA, Botsford LW, et al.2001. Science 293: 629–638
- Klenk NL, Meehan K, Pine SL, Mendez F, Lima PT, et al.2015. Science 350(6262): 743–744
Between social and planetary boundaries: Navigating pathways in the safe and just space for humanityLeach M, Raworth K, Röckstrom J2013. World Social Science Report 2013: Changing Global Environments. UNESCO : 84–90
A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: A systematic analysis for the Global Burden of Disease Study 2010Lim SS, Vos T, Flaxman AD, Danaei G, Shibuya K, et al.2012. Lancet 380: 2224–2260
Seawater acidification and elevated temperature affect gene expression patterns of the pearl oyster Pinctada fucataLiu W, Huang X, Lin J, He M2012. PLoS ONE 7(3): e33679
- Lobell DB, Burke MB, Tebaldi C, Mastrandrea MD, Falcon WP, et al.2008. Science 319: 607–610
- McCauley DJ, Pinsky ML, Palumbi SR, Estes JA, Joyce FH, et al.2015. Science 347(6219): 247–214
Shellfish face uncertain future in high CO2 world: Influence of acidification on oyster larvae calcification and growth in estuariesMiller AW, Reynolds AC, Sobrino C, Riedel GF2009. PLoS ONE 4(5): e5661
- Moore FC, Lobell DB2014. Nat Clim Change 4: 610–614
- Mychajliw AM, Kemp ME, Hadly EA2015. The Anthropocene Review 2(3): 267–278
- Newbold RR, Padilla-Banks E, Jefferson WN2009. Mol Cell Endocrinol 304: 84–89
- Ng KL, Obbard JP2006. Mar Pollut Bull 52(7): 761–767
- PAS and PASS2014. Proceedings of the Joint Workshop Extra Series 41
- Pimm SL, Abell CNJ, Brooks TM, Gittleman JL, Joppa LN, et al.2014. Science 344
- Pimm SL, Raven P, Peterson A, Sekercioglu ÇH, Ehrlich PR2006. P Natl Acad Sci USA 103(29): 10941–10946
- PRB2015. Population Reference Bureau. Accessed 14 June 2015.
- Qiu J2013. Nature 493: 144–145
Spillover: Animal Infections and the Next Human PandemicQuammen D2012. New York: W.W. Norton & Company
Executive Summary of the Report, Bending the Curve: 10 scalable solutions for carbon neutrality and climate stabilityRamanathan V, Allison J, Auffhammer M, Auston D, Barnosky AD, et al.2015. Oakland, CA: University of California Office of the President
A safe and just space for humanityRaworth K2012. Oxfam Discussion Paper February 2012: 1–26
- Ray DK, Mueller ND, West PC, Foley JA2013. PLoS ONE 8(6): e66428
- Rockström J, Steffen W, Noone K, Persson Å, Stuart Chapin F III, et al.2009. Nature 461: 472–475
- Running SW2012. Science 337: 1458–1459
- Ryan PG, Moore CJ, Franeker JAV, Moloney CL2009. Philos Trans R Soc B 364(1526): 1999–2012
- Shah A2011. Global Issues
- Shah A2013.
- Sherwood SC, Huber M2010. P Natl Acad Sci 107: 9552–9555
- Smil V2011. Popul Dev Rev 37(4): 613–636
- Smith WK, Zhao M, Running SW2012. Bioscience 62: 911–922
The World’s Worst Pollution Problems 2012Staff BI2012. New York: Blacksmith Institute
- Steffen W, Persson Å, Deutsch L, Zalasiewicz J, Williams M, et al.2011. AMBIO: A Journal of the Human Environment 40(7): 739–761
Climate and Social Stress: Implications for Security AnalysisSteinbruner JD, Stern PC, Husbands JL2012. Washington, D.C: National Academies Press
Nature’s Fortune: How Business and Society Thrive by Investing in NatureTercek MR, Adams JS2013. New York: Basic Books
Adverse weather conditions for European wheat production will become more frequent with climate changeTrnka M, Rötter RP, Ruiz-Ramos M, Kersebaum KC, Olesen JE, et al.2014. Nat Clim Change 4: 637–643
- Tyrrell T2011. Philos Trans R Soc A 369(1938): 887–908
- Under2MOU2015. Under 2 MOU
World Population Prospects: The 2012 Revision, Volume I: Comprehensive TablesUNDESA2013a. New York: United Nations, Department of Economic and Social Affairs, Population Division
World Population Prospects: The 2012 Revision, Volume II, Demographic ProfilesUNDESA2013b. New York: United Nations, Department of Economic and Social Affairs, Population Division
- Urban MC2015. Science 348(6234): 571–573
Encyclical Letter Laudato Si of the Holy Father Francis on Care for Our Common HomeVatican2015. Vatican City, Rome: The Vatican
- Vitousek PM, Ehrlich PR, Ehrlich AH, Matson PA1986. BioScience 36: 368–373
- Vitousek PM, Mooney HA, Lubchenco J, Melillo JM1997. Science 277: 494–499
- WBSCD2013a. World Business Council for Sustainable Development
- WBSCD2013b. World Business Council for Sustainable Development
- West PC, Gerber JS, Engstrom PM, Mueller ND, Brauman KA, et al.2014. Science 345: 325–328
- White JWC, Alley RB, Archer DE, Barnosky AD, Foley J, et al.2013.
- WHO2011. World Health Organization Media Center
- WHO2013. Millennium Development Goals
- WWF2012. Gland, Switzerland: World Wildlife Fund International
- WWF, ZSL, GFN, WFN2014. Gland, Switzerland: WWF
- Young HS, Dirzo R, Helgen KM, McCauley DJ, Billeter SA, et al.2014. P Natl Acad Sci USA 111(19): 7036–7041
- Zarfl C, Fleet D, Fries E2011. Mar Pollut Bull 62(8): 1589–1591
- Zarfl C, Matthies M2010. Mar Pollut Bull 60(10): 1810–1814