Crop yields and animal productivity are well below the European Community average because of low agricultural investment, minimal machinery, little use of fertilizer and the fragmented land-tenure system. The main crops grown in Portugal are cereals (wheat, barley, corn and rice), potatoes, grapes (for wine), olives and tomatoes. Portugal is the world's largest exporter of tomato paste and a leading exporter of wines. These exports help offset the cost of imported wheat and meat. One-third of Portugal is forested. Most of the mountainous areas are well suited to forestry, and forest products (cork, resins and pine and eucalyptus timber), the market value of which has increased, find a growing demand for the industry. Portugal's long coastline and the abundance of fish in the surrounding waters have favoured the development of the fishing industry. Sardines, anchovies and tuna caught near the coasts, together with other species such as codfish from the North Atlantic, make a large contribution to food supplies. The fish industry has prospered and its products are exported all over the world.