Natural gas has become an important source of energy and economic activity in north central Arkansas. Hydraulic fracturing in the Fayetteville Shale has impacted much of the region's economy, including Cleburne, Conway, Faulkner, Van Buren, and White counties.[24] The state ranked 12th in terms of marketed production of natural gas in 2007.[25] However, health and environmental concerns, including the possible responsibility for earthquakes called the Guy-Greenbrier earthquake swarm have slowed the continued development of activity in the region.[26][27][28]