As resource conflicts grow, resource managers are increasingly faced with trade-offs among environmental assets. The management of the Columbia River system in the US Pacific Northwest is illustrative of such conflict. The Columbia River was developed to provide benefits of flood control, irrigation, municipal and industrial water use, navigation, recreation, and electrical power. The river has long been managed to maximize its power benefits. However, the river's development has adversely affected one of its greatest resources-salmon-bringing several species to the brink of extinction. Today, the river is managed to accord salmon the highest priority. Consequently, the power system has lost much of the flexibility it formerly enjoyed, and because of those changes replacement power sources are needed. Simultaneously, concern with greenhouse gases, principally carbon dioxide has grown. This paper illustrates the conflicts resource managers face when attempting to develop cost-effective new power resources, avoid further carbon emissions, and save the salmon from extinction. It shows that constraints imposed by efforts to save salmon make it much more difficult to achieve another environmental goal, the reduction of carbon emissions.