It was interesting to hear his observation about southern India. The entire densely populated southern part of the country didn't have a major impact on aquatic plant diversity because there were not a lot of waste dumped into the rivers. There were no factories or large industries dumping toxic waste into the rivers. I can see from the pictures in this link that the water in the rivers are clear, interesting plants like Fissidens, Eriocaulon and Microsorum grow well.
https://plus.google.com/photos/10983...12161418649985