In the 1990s Ma became known as an investigative journalist, working at the
South China Morning Post from 1993 to 2000. There, he began to specialize in articles on environmental subjects. He eventually became the Chief Representative of
SCMP.com in
Beijing. Ma's 1999 book ''China's Water Crisis'' (Zhongguo shui weiji) has been compared to
Rachel Carson's
Silent Spring – China's first major book on the subject of that nation's environmental crisis. He directs the IPE (Institute of Public and Environmental Affairs), which developed the China Water Pollution Map (), the first public database of
water pollution information in China. He also serves as environmental consultant for the Sinosphere Corporation. In 2010, Ma, addressing
air pollution particularly in the wake of efforts made at the time of the
Beijing Olympics, said "many of the government's efforts to curtail pollution had been offset by the number of construction projects that spit dust into the air and the surge in private car ownership." In 2016, Ma Jun appeared in the
National Geographic film,
Before the Flood, directed by
Fisher Stevens and narrated by
Leonardo DiCaprio. == Recognition ==