The researchers used satellite images and mapping technology to study how wetlands in Beijing changed from 1984 to 2008. They found that the total wetland area increased until 1996, then decreased due to dry weather and human activities. Artificial wetlands, like reservoirs and ponds, became more common than natural wetlands. The wetland area started to grow again after 2006, thanks to better policies and more rain. Urbanization and population growth were major factors in the loss of wetlands and water resources.