Environmental activist Zhang Zhengxiang has spent decades trying to protect Dianchi Lake in China’s southwestern Yunnan province. It is the largest freshwater lake in southwest China, but also the country’s most polluted. After decades of monitoring and reporting on polluters, Zhang, who is now in his 70s, saw local officials finally brought to justice for damaging the environment around the scenic lake. The scandal involved more than 1,000 villas that were illegally built in the conservation…