The researchers looked at changes in China's wetland areas from 1999-2001 to 2009-2011. They found that the total wetland area decreased, mainly due to natural wetlands like marshes and lakes shrinking. Marsh and reservoir wetlands decreased in Central and Eastern China, while river and lake wetlands increased in Western China. Changes in river wetlands were linked to forest area and temperature changes, while changes in reservoir wetlands were linked to city construction and temperature changes. This suggests that more forests and higher temperatures helped protect river wetlands, while more city construction and higher temperatures helped protect reservoir wetlands.