Xiangjie Chen’s research while affiliated with Loyola University Maryland and other places

The disparity in environmental impacts across different countries has been widely acknowledged1,2. However, ascertaining the specific responsibility within the complex interactions of economies and consumption groups remains a challenging endeavour3–5. Here, using an expenditure database that includes up to 201 consumption groups across 168 countries, we investigate the distribution of 6 environmental footprint indicators and assess the impact of specific consumption expenditures on planetary boundary transgressions. We show that 31–67% and 51–91% of the planetary boundary breaching responsibility could be attributed to the global top 10% and top 20% of consumers, respectively, from both developed and developing countries. By following an effective mitigation pathway, the global top 20% of consumers could adopt the consumption levels and patterns that have the lowest environmental impacts within their quintile, yielding a reduction of 25–53% in environmental pressure. In this scenario, actions focused solely on the food and services sectors would reduce environmental pressure enough to bring land-system change and biosphere integrity back within their respective planetary boundaries. Our study highlights the critical need to focus on high-expenditure consumers for effectively addressing planetary boundary transgressions.

As China’s economic and population demands grow, the need for biomass imports rises, presenting challenges for sustainable development and global ecosystem protection. Here we examine China’s increasing influence on global ecosystems through its biomass product consumption and trade using the Human Appropriation of Net Primary Productivity framework, analyzing data from 2004 to 2017 with projections until 2050. In 2017, China was the world’s largest biomass consumer, consuming approximately 1.75 petagrams of carbon per year, projected to rise by 317.6% by 2050, highlighting China’s major role in global ecosystem stress. Our findings also show an increase in biomass imports from lower-middle-income and low-income countries between 2004 and 2017, and these imports are expected to continue increasing by 402.9% in 2050. The analysis reveals that domestic product demand and changes in foreign production efficiency are key drivers of this trend, suggesting the need for China to shift towards more efficient trade practices and support cleaner production methods internationally.

Understanding the impact of climate fiscal policies on vulnerable groups is a prerequisite for equitable climate mitigation. However, there has been a lack of attention to the impacts of such policies on the elderly, especially the low-income elderly, in existing climate policy literature. Here, we quantify and compare the distributional impacts of carbon pricing on different age–income groups in the United States, the United Kingdom, and Japan and then on different age groups in other 28 developed countries. We find that the elderly are more vulnerable to carbon pricing than younger groups in the same income group. In particular, the low-income elderly and elderly in less wealthy countries face greater challenges because carbon pricing lead to both higher rate of increase in living cost among low-income elderly and greater income inequality within the same age group. In addition, the low-income elderly would benefit less than the younger groups within the same income group in the commonly proposed carbon revenues recycling schemes. The high vulnerability of the low-income elderly to carbon pricing calls for targeted social protection along with climate mitigation polices toward an aging world.

There has been a longstanding debate about the impact of international trade on the environment and human well-being, yet there is little known about such environment and human well-being trade-off. Here, we explore the effect of international trade on the carbon intensity of human well-being (CIWB) globally under the current global trade system and a hypothetical no-trade scenario. We found that between 1995 and 2015, CIWB of 41% of countries declined and 59% of countries increased, caused by international trade, and this resulted in a reduction of the global CIWB and a decline in CIWB inequality between countries. International trade decreased CIWB for high- and upper-middle-income countries and increased CIWB for lower- and middle-income countries. In addition, our results also show that decreases in emission intensity are the most important driver of lower CIWB and the percentage contribution of emission intensity to the improvement in CIWB increases with income. The reduction of emission intensity, population growth, and increase in life expectancy all contribute to CIWB reduction, while the consumption level is the primary factor driving CIWB growth. Our results underscore the importance of studying the impact of international trade on the CIWB of countries at different stages of development.

Carbon taxation is regarded as an essential tool for curbing carbon emissions but can be regressive and increase poverty, and moreover lacks universal acceptance among the public and policymakers. Recycling the tax revenue raised to vulnerable households is one promising solution to this issue. However, little is known about the best strategy for designing such a policy at the global level. This paper investigates the effectiveness of various carbon taxation methods and revenue recycling mechanisms in reducing poverty and inequality between and within countries. We find that the policy mix with the highest poverty reduction potential is implementing a consumption tax with higher tax rates on luxury goods and recycling revenue through expanded social assistance systems, in line with the expansion during the COVID-19 pandemic. While differentiating tax rates across goods within countries is advantageous, the average tax level across countries is best kept uniform since it potentially offers governments in low- and middle-income countries more financial capacity to support the poor. Furthermore, collecting a global climate fund from developed countries and redistributing it to developing countries based on poverty headcounts can further significantly reduce poverty and inequality within and between countries. However, substantial improvements in social assistance systems are urgently needed to further unlock the poverty-reduction potential of revenue recycling, particularly in Sub-Saharan African countries. Also, recycling carbon tax revenues to combat poverty and inequality will inhibit the emission reduction effect of carbon taxation in the short term, necessitating additional mitigation efforts in other areas.

Decoupling economic growth from resource use and emissions is a precondition to stay within planetary boundaries. Some countries have achieved a reduction in their production-based emissions in the past decade. However, the decline in PBE has often been achieved via outsourcing of emissions to other countries, which may lead to higher emissions globally. Therefore, a consumption-based perspective that accounts for a country's emissions along global supply chains should also be employed when investigating progress in decoupling. Here we investigate the progress countries made in reducing their production-based and consumption-based emissions despite growth in the gross domestic product (GDP). We found that 32 out of 116 countries (mainly developed ones) achieved absolute decoupling between GDP and production-based emissions in recent years (2015-2018), and 23 countries achieved absolute decoupling between GDP and consumption-based emissions. 14 countries have decoupled GDP growth from both production- and consumption-based emissions. Even countries that have achieved absolute decoupling are still adding emissions to the atmosphere thus showing the limits of ‘green growth’ and the growth paradigm. We also observed that decoupling can be temporary, and decoupled countries may switch back to increasing emissions, which means that continuous efforts are needed to maintain decoupling. An analysis of driving factors shows that whether a country can achieve decoupling mainly depends on reducing emission intensity along domestic and import supply chains. This highlights the importance of decarbonizing supply chains and international collaboration in controlling emissions.