Bradshaw et al. (2010) developed a ranking of 228 countries according to their environmental impact. Although they avoid overtly defining what is meant by impact, their ranking aims to position countries according to performance with respect to their relative resources and the global impact in terms of resource consumption. They also seek to evaluate whether the signal they derive from their ranking is consistent with other indices of environmental performance, including the Environmental Performance Index, and other indicators, including population size, governance quality and wealth. Finally, they aim to provide some understanding as to whether an "Environmental Kuznets Curve" hypothesis holds with respect to level of economic development and environmental impact.
In describing their rationale for developing an alternative ranking of environmental impact, the authors point to a common challenge with respect to indices in their limitations to be comprehensive, cover the complexities inherent to sustainable development, and arbitrary or subjective assumptions regarding statistical decisions. They also point to the fact that many indices, like the Human Development Index (HDI), which incorporates indicators of human health and economic performance, which often have the impact of diluting the environmental component of such measures, although the HDI doesn't necessarily aim to explicity evaluate environmental performance.
To evaluate the environmental component, the authors use data on Natural Forest Loss, Natural Habitat Conversion, Marine Captures, Fertilizer Use, Water Pollution, Carbon Emissions, and Biodiversity Threat. They point to gaps in variables that evaluate bushmeat extraction, coral reef quality, seagrass change, and freshwater habitat loss given a lack of country-specific data.
For the 179 countries with sufficient data, the authors find that countries with the highest proportional impact is as follows: Singapore, Korea, Qatar, Kuwait, Japan, Thailand, Bahrain, Malaysia, the Philippines and the Netherlands. Most of these countries are found in East and Southeast Asia. The countries with the lowest proportional impact are primarily located in sub-Saharan Africa, including Eritrea, Suriname, Lesotho, Turkmenistan, Gabon, Kazakhstan, Mali, Vanuatu, Chad and Bhutan.
In terms of countries' absolute rankings or those with the most influential environmental impact in a global perspective, the authors found that in general the most populous and economically influential countries dominated. Brazil, the United States, China, Indonesia, Japan, Mexico, India, Russia, Australia and Peru were the ten-worst ranked countries. These results may not be surprising, as the authors point out, considering the large populations, trade relationships, and consumption patterns in these countries.
In evaluating the relationship of their ranking with other measures, Bradshaw et al. (2010) found a positive relationship between the EPI and HDI measures and environmental impact. What this result suggests is that countries with a higher EPI score tend to have higher environmental impact.
In terms of socioeconomic indicators, including human population size and growth, wealth, and governance quality (as measured by the Worldwide Governance Indicators), the authors found that countries with higher total human populations and densities had greater proportional environmental impact. Singapore's worst-ranking confirms this observed trend, as one of the most densely-populated nations at 7,713 people per sq. km (the United States' population density is 35 people per sq. km by comparison). Countries with greater total wealth (as measured by per capita PPP-adjusted GNI, see Figure below) have worse environmental impact than poorer countries.
Last, the authors find no support for an EKC hypothesis - a non-linear relationship was observed between environmental impact and per capita wealth, although they did find a weak reduction in environmental impact as per capita wealth increases (see Figure).
The authors conclude that "the global community not only has to encourage better environmental performance in less-developed countries, especially in Asia," but more is needed to require the development of such practices in wealthier countries. They point to populous countries undergoing rapid economic development, including China, India, and Indonesia, that might have the fastest increases in environmental impact and where better management practices and policies are needed.
Figure 1. The authors find no clear linear relationship between wealth and environmental impact, suggesting no evidence to support an Environmental Kuznets Curve.