This loose society of volunteers gathers here at the river mouth once a month on Tuesday mornings to help restore the San Diego River Estuary, a delicate coastal ecosystem. Specifically, the aims include protecting native and endangered plant- and wildlife and preserving and improving water quality. The event is organized by the San Diego River Park Foundation, whose ambitious goal is to restore a green belt along all 52 miles of the San Diego River. The fence-building group, limited in capacity, was full before I had registered that I had a choice, so I joined the invasive plant removers. The next river mouth habitat restoration will be Tuesday, September 23rd.