Total forest area amounted in 2000 to over 10.7 million hectares(26.5 million acres), about 31% of the total land area. Reforestation has resulted in a 6% increase in the forest area since the end of World War II (1939–45). Deciduous species (such as beech, oak, ash, maple, and alder) originally covered about two-thirds of the area, and conifers were only predominant in higher elevations. Today, hardwood trees comprise only one-third of the forests. Principal softwood species include silver fir, pine, spruce, and Douglas fir, which was introduced from the northwest United States late in the 19th century. The most thickly wooded of the federal Länder are Hessen and Rhineland-Pfalz. A total of 33,400,000 cu m of timber was cut in 2001. The harvest represented about 70% of Germany's annual rate of wood regrowth. Consumption of timber by the wood working industry is 39–42 million cu m (1.4–1.5 billion cu ft) per year. Total trade in forest products during 2000 included $10.8 billion in imports and $9.9 billion in exports. Output of paper and paperboard totaled 18.18 million tons in 2000, fifth highest after the United States, China, Japan, and Canada. High domestic labor costs compel Germany to import substantial quantities of value-added products such as veneers and panels.