Introducing freshwater to a globally important mangrove forest in China may help establish reedbeds, but it may not sustain the mangrove trees in the long run, according to research by environmental science major Juan Navarro ’17.
The Mai Po Nature Reserve, near Hong Kong, is important to many native animals and a haven for migratory birds. Every year, tens of thousands of them take refuge in the reserve’s marshes and mudflats. With the hope of providing suitable environments for the freshwater wildlife, such as amphibians and wintering ducks, the World Wildlife Fund has created freshwater ponds on the southern end of the reserve, where historically a freshwater marsh used to be.
Navarro’s research, though, suggests that the less salty water may not sustain the mangroves in the long term. He and Whittier College Professor of Biology Cheryl Swift recently traveled to the reserve to study the plants’ ability to thrive in salty water versus freshwater.
After checking trees before dawn, then again at midday, Navarro and Swift found a difference in the water stress of several species: River Mangrove, Kandelia, and Spiny Bears Breech. The mangroves fared notably better in the salty water than in the freshwater ponds, or even the intertidal zone where ocean water constantly flushes into the area, according to their study.
While freshwater may facilitate the establishment of reed beds, an important habitat for birds, it is not likely to sustain the mangroves over the long term. Navarro and Swift are hopeful that the data they have collected will be useful for future Mai Po reserve management plans.
