The good news: In a report card on the health of the Chesapeake Bay, 2015 turned out to be the best non-drought year since 1992, representing a third consecutive year of growth.

The bad news: The overall grade, given by researchers at the University of Maryland’s Center for Environmental Science, was still only a C (53 percent), with conditions listed as “poor to moderate.”

What should we take away from this report? First, efforts to improve water quality and protect the bay’s delicate ecosystem appear to be working. The Chesapeake Bay Preservation Act and subsequent attempts at reducing point and non-point sources of pollution have only been in place for a relatively short time, and yet are already bearing fruit.

Secondly, we still have a long way to go. When John Smith first laid eyes on the Chesapeake Bay in 1608, oysters “lay as thick as stones” and the bay and its tributaries contained more sturgeon “than could be devoured by dog or man...