China's environmental crisis is one of the most pressing challenges to emerge from the country's rapid industrialization. Its economic rise, which has averaged around 10 percent annual GDP growth for the past decade, has come at the expense of its environment and public health. As the world's largest source of carbon emissions, China is responsible for a third of the planet's greenhouse gas output and has sixteen of the world's twenty most polluted cities. Life expectancy in the north has decreased by 5.5 years due to air pollution, and severe water contamination and scarcity have compounded land deterioration problems. Environmental degradation cost the country roughly 9 percent of its gross national income in 2008, according to the World Bank, threatening to undermine the country's growth and exhausting public patience with the government's pace of reform. It has also bruised China's international standing as the country expands its global influence, and endangered its stability as the ruling party faces increasing media scrutiny and public discontent.