Executive Order: On May 12, President Obama issued an executive order to protect and restore the health, heritage, natural resources, and economic and social value of the Chesapeake Bay. NRDC experts discuss what the order means for the nation's largest estuary, as well as for the protection and restoration of other aquatic environments across the country.

Heavy rains can carry contaminants into the water, from toxic metals to herbicides, pesticides, and bacteria. The federal government is the largest landowner in the watershed, so improvements at federal facilities -- such as green roofs, rain gardens, and permeable pavements -- will make a difference.

What happens on land determines the bay's health. We must be willing to invest public dollars to preserve as many of the remaining marshes, swamps, and forests as possible and reduce pollution flowing into streams that feed the bay. If these ecosystems thrive, the bay will survive.

We don't have a good understanding of how water moves through the Great Lakes watersheds and into the lakes, so basic scientific research on the hydrology of the Chesapeake Bay watershed will help us understand the Great Lakes as well. We can't fix or protect an ecosystem until we understand these basic concepts.

Climate change will likely increase the frequency of intense rainfalls, which wash contaminants into the bay, exacerbating algal blooms that create oxygen-deprived "dead zones." Strengthening regulation of pollution sources would help protect water quality for the watershed's 17 million residents.

Photos: Matt Greenslade (Stoner); Lisa Whiteman (Perks, Henderson); Leslie von Pless/Women’s Media Center (Knowlton)