Every summer, parts of the Chesapeake Bay die. Nitrogen and phosphorus runoff from upstream farms consume all of the water’s oxygen, suffocating fish, crabs, and other marine life. To combat this problem, the U.S. Environmental Protection Agency (EPA) imposes strict limits on the amount of nitrogen and phosphorous that can enter rivers that feed the Bay. But rules are only as good as their enforcement. The EPA recently found, for example, that only 30 percent of the nearly 40,000 farms in Pennsylvania, whose rivers supply 35 percent of the Bay’s water, comply with regulations that cap the runoff of nitrogen- and phosphorus-rich manure and fertilizer. Since the EPA released its finding, Pennsylvania regulators have weighed multiple strategi...