The many values that humans place on biodiversity are widely acknowledged but difficult to measure in practice. We address this problem by quantifying the contribution of marine-related environmental stewardship, in the form of donations and volunteer hours, to the economy of coastal Massachusetts. Our conservative evaluation suggests that marine stewardship activities contributed at least 179milliontothestateeconomyin2014,afigurethatexceededrevenuesderivedinthatsameyearfromcommercialfinfishoperations(105 million) and whale watching ($111 million), two acknowledged cornerstones of the regional economy. Almost imperceptibly, the coastal economy has been transformed from one dependent on commercial exchange to a diverse economy that includes, to a large measure, marine stewardship. Donations and volunteer efforts are useful indicators of environmental values that can be hard to quantify, and represent one measure of human determination to protect the planet