This is when I noticed a layer of bright orange clay coated the area from a nearby construction site.
The mangroves grow along the waterway marked with the yellow line. I noticed a bright orange clay trail in the drain to the west (red line) of Punggol Road. While the water in the drain to the east (blue line) was normal, no bright orange clay trail.
In Aug 2015, I was already worried that plans for the Singapore Institute of Technology (SIT) may affect the Punggol mangroves.
Overlaying the graphic on Google Earth, it appears there will be new roads (blue). The northern road appears to cut close to a tiny sliver of wild mangroves there (yellow dot). I last visited this mangrove patch in Feb 2011.
We lose our natural mangroves and ecosystems by inches. As they degrade with impacts from developments nearby, it becomes easier to write them off as being in too poor a state to conserve. Sigh.