Forest products have always been a staple to the economy, comprising 1% of the total gross state output and 9% of total manufacturing as of 2013. In 2007, Windham County contained the largest concentration of kilns for drying lumber east of the Mississippi River. The decline of farms has resulted in a regrowth of Vermont's forests due to ecological succession. Today, most of Vermont's forests are secondary. The state and non-profit organizations are actively encouraging regrowth and careful forest management. Over 78% of the land area of the state is forested compared to only 37% in the 1880s, when sheep farming was at its peak and large amounts of acreage were cleared for grazing. Over 85% of that area is non-industrial, private forestland owned by individuals or families. In 2013, of wood was harvested in Vermont. A large amount of Vermont forest products are exports with being shipped overseas plus an additional to Canada. Most of it was processed within the state. In this century the manufacture of wood products has fallen by almost half. The annual net growth has been estimated at . The USDA estimates that remain in the state. Forest products also add to carbon sequestration since lumber and timber used in houses and furniture hold carbon for long periods of time while the trees that were removed are replaced overtime with new growing stock.