The wetlands in the Sanjiang Plain of northeast China have been shrinking, so researchers used satellite images to study four wetlands. They found that the wetland area decreased a lot from 1984 to 2013, and natural water inflow isn't enough for the wetlands. By calculating how much water the wetlands need and how much artificial water recharge is needed, they found that the wetlands need help to survive. This study provides important information for protecting and restoring wetlands in the area, which is crucial for rare waterfowl to have a good habitat.