Tulare County, California, recently surpassed nearby Fresno County as the top agriculture-producing county in terms of economic value within the U.S. It’s also the country’s top dairy producing county. The result has been more investment and economic growth in a rapidly booming area already home to 450,000 people.But there is also a downside to the local dairy industry’s continued surge: The San Joaquin Valley suffers from some of worst air pollution in the U.S., and cow effluent is a threat to the region’s already troubled watersheds.