Human impacts on earth-system processes are overshooting several planetary boundaries, driving a crisis of ecological breakdown. This crisis is being caused in large part by global resource extraction, which has increased dramatically over the past half century. We propose a novel method for quantifying national responsibility for ecological breakdown by assessing nations’ cumulative material use in excess of equitable and sustainable boundaries.
For this analysis, we derived national fair shares of a sustainable resource corridor. These fair shares were then subtracted from countries’ actual resource use to determine the extent to which each country has overshot its fair share over the period 1970–2017. Through this approach, each country’s share of responsibility for global excess resource use was calculated.
High-income nations are responsible for 74% of global excess material use, driven primarily by the USA (27%) and the EU-28 high-income countries (25%). China is responsible for 15% of global excess material use, and the rest of the Global South (ie, the low-income and middle-income countries of Latin America and the Caribbean, Africa, the Middle East, and Asia) is responsible for only 8%. Overshoot in higher-income nations is driven disproportionately by the use of abiotic materials, whereas in lower-income nations it is driven disproportionately by the use of biomass.
These results show that high-income nations are the primary drivers of global ecological breakdown and they need to urgently reduce their resource use to fair and sustainable levels. Achieving sufficient reductions will likely require high-income nations to adopt transformative post-growth and degrowth approaches.
Human impacts on earth-system processes are overshooting several planetary boundaries, not only in terms of CO2 emissions and climate change, but also land-use change, biodiversity loss, chemical pollution, and biogeochemical flows.1, 2, 3, 4 The current rate of biodiversity loss is particularly concerning; in a comprehensive review of extant evidence, the UN Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services found that, on our present trajectory, around one million species are now at risk of extinction, many within decades.5 This trend is indicative of widespread habitat fragmentation, ecosystem disruption, and ecological breakdown. These problems are being driven in large part by global resource use, through processes of material extraction, production, consumption, and waste. Resource use has a range of impacts on terrestrial and marine ecosystems, including on forests, soils, wetlands, lakes, rivers, and oceans, and resource use is understood to be a robust proxy for environmental pressure.6, 7, 8 Steinmann and colleagues 9 showed that resource use accounts for more than 90% of the variation in environmental damage indicators. The UN International Resource Panel found that resource use is responsible for 90% of total global biodiversity loss and water stress.10 Moreover, as van der Voet and colleagues showed,11 although impacts vary by material and as technologies change, there is a link between aggregate mass flows and ecological impact, with a correlation coefficient of 0·73.11 Although differences between individual materials are important, aggregate material use is a key indicator for environmental policy.12
Global material use has increased markedly over the past half century, to the point where, as of 2017, the world economy is consuming over 90 billion tonnes of materials per year—well in excess of what industrial ecologists consider to be the sustainable limit. This increasing trend holds across all categories of materials, including biomass, metals, non-metallic minerals, and fossil fuels.13 However, not all nations are equally responsible for this trend; some nations use substantially more resources per capita than others.14
Although previous research has explored the question of national responsibility for CO2 emissions and climate change,15, 16 such analysis has not been applied to other forms of environmental pressure. In this study, we quantify national responsibility for ecological damages related to excess material use, using a method rooted in the principle that the planet’s resources and ecosystems are a commons, and that all people are entitled to an equal, sustainable share. This principle has been articulated in the climate literature,17, 18 and the approach used here builds on a method that was developed for CO2 emissions.15
Research in context
Evidence before this study
Existing research has shown that global resource use markedly exceeds sustainable levels and is driving a crisis of ecological breakdown, endangering planetary health. Research has also found that higher-income nations have higher per capita resource use than lower-income nations, and these nations also exceed sustainability thresholds to a greater extent. However, to date there has been no attempt to quantify national responsibility for the cumulative excess of global resource use that is driving the ecological crisis.
Added value of this study
This study advances existing research by assessing the extent to which nations exceed equitable and sustainable resource use corridors, in terms of cumulative material consumption. The study uses these data to quantify national responsibility for excess global resource use over the period 1970–2017. The study proceeds on the principle that all people have the right to an equitable fair share of global resource use at a sustainable level, drawing on the logic of the commons as developed in the climate literature.
Implications of all the available evidence
The results of this analysis indicate that high-income nations are the primary drivers of global ecological breakdown and must urgently reduce their resource use to fair and sustainable levels. Given existing evidence on the strong coupling between economic growth and resource use, this will likely require high-income nations to adopt transformative post-growth and degrowth approaches.
Quantifying material use
Two primary methodological issues require attention. The first is the extent to which a nation’s resource use can reasonably be considered to contribute to ecological breakdown on a global level. With CO2 emissions, national emissions have global effects. Something similar is true of resource use, given the reality of international trade—particularly in an era of globalisation and complex commodity supply chains. Material flows data reveal that the products consumed in any given country rely on resources extracted from many countries around the world.19 An iPad, for instance, involves materials from 748 international suppliers.20 Consumption of iPads and similar items in the USA or Sweden has impacts in countries ranging from China to Bolivia to DR Congo. Global economic integration, and the globalised nature of resource supply chains, makes it necessary to think about national resource use in terms of aggregate global ecological pressure.21
For quantifying national use of material resources, two indicators are available. One is domestic material consumption (DMC), which represents the total mass of material extraction within a nation’s borders, plus the mass of imports, minus the mass of exports. Although this metric accounts for trade to some degree, it does not include the upstream material extraction required to produce traded goods. The second metric is material footprint (MF), also known as raw material consumption. MF accounts not only for domestic extraction and the mass of traded goods, but also for the upstream material extraction required to produce these goods.21, 22, 23 For example, although DMC includes the mass of an imported smartphone, MF includes the smartphone plus the materials involved in the supply chains that produce it. By accounting for these dynamics, MF represents the total materials embodied in national final demand. Given the dynamics of offshore production and global supply chains, MF data are preferable to DMC data when it comes to assessing the contributions of national consumption to ecological breakdown.
Recognising the international nature of material flows allows us to resolve questions that might arise from a more methodologically territorial perspective. For instance, one might argue that countries such as Finland and Costa Rica should not be penalised for resource use in the same way as countries such as Brazil and the USA, on the grounds that resource extraction in the former countries is more heavily regulated, and uses more sustainable technologies than in the latter countries (ie, represents less ecological impact per tonne of material extracted). But although Finland might apply stronger regulatory standards to its own domestic extraction, it does not apply those same standards to extraction embodied in products and intermediate parts imported from abroad. When accounting for the complexity of global commodity chains, differences in national regulatory frameworks and technological endowments become less important. Consumption in Finland involves resources extracted in Brazil, while consumption in Brazil involves resources extracted in Finland.
Having established that MF allows meaningful assessment of national contributions to extraction-related ecological breakdown, there is a second methodological issue to address. Although all resource use entails ecological pressure, some level of resource use is of course necessary for sustaining human society, and countries with larger populations will therefore require more baseline resource use than countries with smaller populations. Considering this, our focus should not be on national resource use as such—ie, in absolute terms—but rather on some metric of excess resource use, measured with respect to a conception of fair shares that is grounded in principles of equity and sustainability.
One straightforward method to account for equity is to assess the extent to which nations’ per capita resource use exceeds the global mean per capita level. This approach has been used to quantify nations’ contributions to excess global CO2 emissions.16 The limitation of this approach is that although it works for modest levels of global resource use, it makes little sense to assume that aggregate resource use can increase indefinitely. From an ecological perspective, some kind of upper limit or boundary, similar to those that are used in climate policy (such as the 350 ppm planetary boundary, or the 1·5°C and 2°C limits) could be posited, beyond which any additional aggregate resource use would be considered excessive, regardless of how it is distributed.
Quantifying national responsibility
It is impossible to pinpoint precise boundaries for any complex geophysical process; such an exercise will always involve uncertainty and have a normative element. This is true for resource use just as it is for atmospheric CO2 concentrations, ocean pH, land-use change, and other processes represented in the planetary boundaries framework. However, the boundary is somewhere, and it is clear that it has already been exceeded. Industrial ecologists have proposed that a sustainable boundary for global resource use might be around 50 billion tonnes per year.24, 25, 26, 27, 28 Global resource use exceeded this level in 1997. This level is generally considered to be an upper-limit boundary; Bringezu proposes a target sustainability corridor of about 25–50 billion tonnes per year (Gt/a).27 Global resource use exceeded 25 Gt/a in 1970.
We operationalised this sustainability corridor as follows. When aggregate global resource use was between 25 Gt/a and 50 Gt/a (ie, for the years 1970–96) we set the boundary at the level of global resource use in each year. Thereafter, we used the 50 Gt/a upper limit (ie, for the years 1997 and thereafter). Building on methods developed by Fanning and O’Neill,28 O’Neill and colleagues,29 and Hickel,15 we distributed the boundary according to each country’s population as a share of the global population, in other words, on an equal fair-share basis, in keeping with the principle of ecological commons. Population data were obtained from the World Bank.30 This approach allows us to determine each country’s fair share of the boundary in each year. Note that these fair shares are not static; they change over time t as populations change, as follows:
In years when national resource use was larger than the national fair share, the difference between these quantities was used to calculate overshoot, as follows:
In all other years, overshoot was defined as zero, so that undershoot in one year does not compensate for overshoot in other years. Summing national overshoots over the period from 1970–2017 yielded each nation’s cumulative overshoot. Finally, dividing each nation’s cumulative overshoot by the sum of all nations’ cumulative overshoots (ie, cumulative global overshoot) allowed us to quantify national responsibility for total excess resource use:
Role of the funding source
There was no funding source for this study.
Nearly 2·5 trillion tonnes of materials were extracted and used globally from 1970–2017, with high-income and upper–middle-income countries using the vast majority of the resources. Of this, 1·1 trillion tonnes were in excess of the sustainable corridor. High-income countries (according to the World Bank classification) were collectively responsible for 74% of cumulative excess material use, and upper–middle-income countries were responsible for 25% of cumulative excess material use. Lower-middle-income countries and low-income countries were collectively responsible for less than 1% (figure 1).
Table 1 shows the share of responsibility for cumulative excess resource use, both for individual countries and income groups. Full country results are available in appendix 1 and regional aggregates are shown in appendix 2. The results indicate that the USA is the single largest contributor to excess resource use and is responsible for 27% of the world total. EU countries and the UK are together responsible for 25% of the world total of excess resource use. China, an upper–middle-income country, is responsible for 15%, and the rest of the Global South (ie, the low-income and middle-income countries of Latin America and the Caribbean, Africa, the Middle East, and Asia) is responsible for 8%. There are 58 countries, representing 3·6 billion people, that have remained within their fair shares of the boundary over the whole period from 1970–2017 (including India, Indonesia, Pakistan, Nigeria, Bangladesh, and other large populous countries), and therefore bear no responsibility for excess resource use, according to our analysis.
National responsibility for excess resource use has changed over the period analysed. Although the USA’s overshoot has grown consistently in absolute terms, its share of global overshoot has gradually diminished over the past two decades. A similar trend is visible for Europe and other high-income nations. This change is due primarily to increasing resource use in China, which is mostly comprised of construction materials. China’s overshoot began only in 2001, but has grown rapidly in the years since (figure 2).
For comparison, we also tested higher and lower upper-limit boundaries for annual resource use, with a 20% shift in either direction, to assess the extent to which outcomes are sensitive to this parameter. Our results show that the share of responsibility does change slightly, although it does not alter the overall pattern of our findings (appendix 2). With the lower boundary, the responsibility of lower-income nations generally increases (because more of them have resource use that exceeds the boundary), while the responsibility of higher-income nations declines accordingly. With the higher boundary, the opposite occurs: higher-income nations have a greater share of responsibility.
The fair-shares approach articulated here offers a novel method for quantifying national responsibility for ecological breakdown. High-income countries, which represent only 16% of the world population, are responsible for 74% of resource use in excess of fair shares and are therefore the primary drivers of global environmental degradation, representing a process of ecological colonisation.18 Furthermore, the majority of the ecological pressure from excess consumption in rich nations is outsourced to poorer nations. According to a recent analysis, more than 50% of excess consumption in rich nations is net appropriated from poorer nations in the Global South.32 This appropriation not only causes ecological damage in poorer nations, but depletes them of the material resources that they could otherwise use to provide for human needs and expand their sovereign industrial capacity.19
Our results show that high-income nations need to urgently scale down aggregate resource use to sustainable levels. On average, resource use needs to decline by at least 70% to reach the sustainable range. Such reductions will require strong legislation on both domestic extraction and material footprints. The European Parliament recently took steps in this direction by calling on the European Commission to adopt binding targets to reduce resource footprints by 2030 and bring them within planetary boundaries by 2050.33
It is unlikely that such reductions can be achieved while pursuing economic growth. There is no evidence of long-term absolute decoupling of economic growth from resource use occurring either in historical data or in modelled projections, even under high-efficiency scenarios.8, 34, 35, 36 Indeed, global gross domestic product (GDP) and global resource use are tightly coupled, and have increased in parallel for 50 years, despite substantial technological innovation and an increase in the contribution of services to GDP.37 Therefore, the transition to sustainable levels of resource use will probably require adopting transformative post-growth and degrowth approaches, including abandoning GDP growth as a goal, reducing inequality, and organising the economy around human needs, while scaling down unnecessary commodity production.38, 39 Empirical evidence shows that degrowth strategies can be deployed to achieve substantial reductions in resource use while providing good lives for all people.40, 41, 42 However, such a shift will require confronting the powerful network of think tanks, trade associations, lobby groups, philanthropic foundations, and other actors that develop and spread misinformation (such as so-called green growth narratives) in an attempt to legitimise an unsustainable status quo.43, 44, 45
There are three key limitations to the present study that are worth discussing. One is that cumulative overshoot accounting is highly sensitive to the start date of the analysis. Starting in 1970 effectively erases excess resource use that might have happened before this date, which has substantial distributional implications. For instance, the USA has consumed resources in excess of 8 tonnes per capita per year since at least 1870 (when national records began). Resource use in the USA increased particularly rapidly in the middle of the 20th century, more than doubling from 13 tonnes per capita in 1932, to 29 tonnes per capita by 1970, due in large part to infrastructure buildout.46 We can assume that the UK, the EU, and most other high-income nations followed a similar trajectory during the same period, yet excess resource use during this period is absent—effectively forgiven—in the cumulative accounts presented here.
By contrast, nations in the Global South that have industrialised more recently are penalised for the same activity because it happened within the analysis period, and during a period of aggregate resource overuse. This issue is particularly evident in the case of China, where infrastructure buildout has occurred primarily since 2000. If responsibility for excess resource use were to be calculated in a manner that accounted for asynchronous patterns of industrial development, the responsibility of the USA and EU would likely be substantially higher than our results suggest, and the responsibility of countries in the Global South would probably be lower.
This dynamic explains much of the difference between the results of this study and those of a previous study on responsibility for excess CO2 emissions.15 Because the CO2 analysis covered a longer time period (1850–2015), the USA was found to have a higher share of responsibility (40%), whereas China was found to be still within its fair share of the planetary boundary. However, the two studies are not directly comparable because the CO2 emissions overshoot was quantified according to a longitudinal budget, whereas material use overshoot is quantified in this study according to an annualised boundary.
A second limitation has to do with the aggregated nature of the boundaries, particularly for abiotic resource use. The analysis could potentially be deepened by disaggregating abiotic materials (ie, into the constitutive categories of metals, non-metallic minerals, and fossil fuels), so as to determine responsibility for more specific environmental pressures. However, further research is needed to quantify material-specific boundaries that disaggregated values could be compared with.
A third limitation has to do with the annualised nature of the material use boundary. The boundary does not diminish no matter how much—or for how long—it is transgressed. In reality, if we have used too much in the past, less will be available in the future. Ultimately, what matters is how much we are using versus the capacity of ecosystems, a message that indicators such as the ecological footprint continue to convey.47
Other approaches for assigning national fair shares could also be explored to account for differences between countries (eg, colder regions might require more buildings and infrastructure), or to share responsibility for excess resource use between consumers and producers.48, 49 It is also important to note that there is substantial variation of responsibility within countries, given that rich individuals consume more than poor individuals. However, ultimately, a country’s aggregate resource use is an effect of its economic model and provisioning systems, so the concept of responsibility is best understood as pertaining to the national level, where policy decisions and regulatory frameworks are determined.
In conclusion, a fair-shares assessment of resource use shows that high-income nations bear the overwhelming responsibility for global ecological breakdown, and therefore owe an ecological debt to the rest of the world. These nations need to take the lead in making radical reductions in their resource use to avoid further degradation, which will likely require transformative post-growth and degrowth approaches.
JH conceived the study. JH, DWO, and ALF designed the study methodology. DWO, ALF, and HZ collected the data. All authors contributed to the data analysis. JH wrote the original draft of the manuscript. ALF and HZ produced the original study figures. JH, DWO, and ALF reviewed and edited the manuscript. DWO and ALF accessed and verified the data. All authors had full access to all the data in the study and had final responsibility for the decision to submit for publication.
The national-level data collected for this study are publicly available from the UN Environment Programme’s International Resource Panel and the World Bank, as described in the Methods section. The results for all countries are available in appendix 1.
Declaration of interests
We declare no competing interests.
We are grateful to four anonymous reviewers for their helpful comments.
- ↩ Rockström J, Steffen W, Noone K, et al. Planetary boundaries: exploring the safe operating space for humanity. Ecol Soc 2009; 14: 32.
- ↩ Steffen W, Rockström J, Richardson K, et al. Trajectories of the earth system in the anthropocene. Proc Natl Acad Sci USA 2018; 115: 8252–59.
- ↩ Steffen W, Richardson K, Rockström J, et al. Sustainability. Planetary boundaries: guiding human development on a changing planet. Science 2015; 347: 1259855.
- ↩ Persson L, Almroth BMC, Collins CD, et al. Outside the safe operating space of the planetary boundary for novel entities. Environ Sci Technol 2022; 56: 1510–21.
- ↩ IPBES. Global Assessment Report on Biodiversity and Ecosystem Services. Bonn: IPBES secretariat, 2019.
- ↩ Krausmann F, Gingrich S, Eisenmenger N, Erb K-H, Haberl H, Fischer-Kowalski M. Growth in global materials use, GDP and population during the 20th century. Ecol Econ 2009; 68: 2696–705.
- ↩ Eurostat. Material flow accounts statistics—material footprints. 2020. https://ec.europa.eu/eurostat/statistics-explained/index.php/ Material_flow_accounts_statistics_-_material_footprints (accessed March 5, 2022).
- ↩ Haberl H, Wiedenhofer D, Virág D, et al. A systematic review of the evidence on decoupling of GDP, resource use and GHG emissions, part II: synthesizing the insights. Environ Res Lett 2020; 15: 065003.
- ↩ Steinmann Z, Schipper AM, Hauck M, Giljum S, Wernet G, Huijbregts MAJ. Resource footprints are good proxies of environmental damage. Environ Sci Technol 2017; 51: 51.
- ↩ International Resource Panel. Global Resources Outlook 2019: natural resources for the future we want. Paris: International Resource Panel, 2019.
- ↩ Van der Voet E, Oers L, Nikolic I. Dematerialization: not just a matter of weight. J Ind Ecol 2004; 8: 121–37.
- ↩ O’Neill DW. What should be held steady in a steady-state economy? Interpreting Daly’s definition at the national level. J Ind Ecol 2015; 19: 552–63.
- ↩ UN Environment Programme–International Resource Panel. Global Material Flows Database. 2020. https://www.resourcepanel. org/global-material-flows-database (accessed March 5, 2021).
- ↩ Schandl, Fischer-Kowalski M, West J, et al. Global material flows and resource productivity: forty years of evidence. J Ind Ecol 2018; 22: 827–38.
- ↩ Hickel J. Quantifying national responsibility for climate breakdown: an equality-based attribution approach for carbon dioxide emissions in excess of the planetary boundary. Lancet Planet Health 2020;4: e399–404.
- ↩ Matthews HD. Quantifying historical carbon and climate debts among nations. Nat Clim Chang 2016; 6: 60–64.
- ↩ Narain S, Riddle M. Greenhouse Justice: an entitlement framework for managing the global atmospheric commons. London, UK: Anthem Press, 2007: 401–14.
- ↩ Climate Emergency Institute. People’s Agreement of Cochabamba. April 24, 2010. https://www.climateemergencyinstitute.com/ uploads/Peoples_climate_agreement.pdf (accessed March 5, 2022).
- ↩ Dorninger C, Hornborg A, Abson DJ, et al. Global patterns of ecologically unequal exchange: implications for sustainability in the 21st century. Ecol Econ 2021; 179: 106824.
- ↩ Clelland DA. The core of the apple: degrees of monopoly and dark value in global commodity chains. J World-syst Res 2014; 20: 82–111.
- ↩ Wiedmann TO, Schandl H, Lenzen M, et al. The material footprint of nations. Proc Natl Acad Sci USA 2015; 112: 6271–76.
- ↩ Lenzen M, Moran D, Kanemoto K, Geschke A. Building Eora: a global multi-region input–output database at high country and sector resolution. Econ Syst Res 2013; 25: 20–49.
- ↩ Lenzen M, Kanemoto K, Moran D, Geschke A. Mapping the structure of the world economy. Environ Sci Technol 2012; 46: 8374–81.
- ↩ Dittrich M, et al. Green economies around the world: implications of resource use for development and the environment. Vienna: SERI, 2012.
- ↩ Hoekstra AY, Wiedmann TO. Humanity’s unsustainable environmental footprint. Science 2014; 344: 1114–17.
- ↩ UN Environment Programme. Managing and conserving the natural resource base for sustained economic and social development. Nairobi: United Nations Environment Programme, 2014.
- ↩ Bringezu S. Possible target corridor for sustainable use of global material resources. Resources 2015; 4: 25–54.
- ↩ Fanning AL, O’Neill DW. Tracking resource use relative to planetary boundaries in a steady-state framework: a case study of Canada and Spain. Ecol Indic 2016; 69: 836–49.
- ↩ O’Neill DW, Fanning AL, Lamb WF, Steinberger JK. A good life for all within planetary boundaries. Nat Sustain 2018; 1: 88–95.
- ↩ The World Bank. Population, total. https://data.worldbank.org/ indicator/SP.POP.TOTL (accessed March 18, 2022).
- ↩ Daly HE. Toward some operational principles of sustainable development. Ecol Econ 1990; 2: 1–6.
- ↩ Hickel, Dorninger C, Wieland H, Suwandi I. Imperialist appropriation in the world economy: drain from the global south through unequal exchange, 1990–2015. Glob Environ Change 2022; 73: 102467.
- ↩ European Parliament. Report on the New Circular Economy Action Plan. 2021 https://www.europarl.europa.eu/doceo/document/ TA-9-2021-0040_EN.html (accessed March 14, 2021).
- ↩ Hickel J, Kallis G. Is green growth possible? New Polit Econ 2020; 25: 469–86.
- ↩ Vadén T, Lähde V, Majava A, et al. Decoupling for ecological sustainability: a categorisation and review of research literature. Environ Sci Policy 2020; 112: 236–44.
- ↩ Parrique T, Barth J, Briens F, et al. Decoupling debunked—evidence and arguments against green growth as a sole strategy for sustainability. 2019. https://eeb.org/library/decoupling-debunked/ (accessed March 5, 2022).
- ↩ Wiedmann T, Lenzen M, Keyßer LT, Steinberger JK. Scientists’ warning on affluence. Nat Commun 2020; 11: 3107.
- ↩ Kallis G, Kostakis V, Lange S, Muraca B, Paulson S, Schmelzer M. Research on degrowth. Annu Rev Environ Resour 2018; 43: 291–316.
- ↩ European Environment Agency. Growth without economic growth. 2021. https://www.eea.europa.eu/publications/growth-without-economic-growth (accessed March 14, 2022).
- ↩ Lettenmeier M, Liedtke C, Rohn H. Eight tons of material footprint—suggestion for a resource cap for household consumption in Finland. Resources 2014; 3: 488–515.
- ↩ Millward-Hopkins J, Steinberger JK, Rao ND, Oswald Y. Providing decent living with minimum energy: a global scenario. Glob Environ Change 2020; 65: 102168.
- ↩ Hickel, J. Less is more: how degrowth will save the world. London: Penguin Random House UK, 2021.
- ↩ Farrell J, McConnell K, Brulle R. Evidence-based strategies to combat scientific misinformation. Nat Clim Chang 2019; 9: 191–95.
- ↩ Lamb WF, Mattioli G, Levi S, et al. Discourses of climate delay. Glob Sustain 2020; 3: e17.
- ↩ Fanning AL, O’Neill DW, Büchs M. Provisioning systems for a good life within planetary boundaries. Glob Environ Change 2020; 64: 102135.
- ↩ Gierlinger S, Krausmann F. The physical economy of the United States of America: extraction, trade, and consumption of materials from 1870 to 2005. J Ind Ecol 2012; 16: 365–77.
- ↩ Wackernagel M, Lin D, Evans M, Hanscom L, Raven P. Defying the footprint oracle: implications of country resource trends. Sustainability (Basel) 2019; 11: 2164.
- ↩ Steininger KW, Lininger C, Meyer LH, Muñoz P, Schinko T. Multiple carbon accounting to support just and effective climate policies. Nat Clim Chang 2016; 6: 35–41.
- ↩ Li M, Wiedmann T, Fang K, Hadjikakou M. The role of planetary boundaries in assessing absolute environmental sustainability across scales. Environ Int 2021; 152: 106475.