Agriculture involves cultivating plants and animals to produce food, fiber and other products. It began independently in different parts of the world over 10,000 years ago with the domestication of wild grains, pigs, cattle and other species. Modern industrial agriculture uses mechanization, fertilizers and pesticides to sharply increase yields, but has also caused environmental damage. Over one third of the world's workers are still employed in agriculture, mainly in developing countries, though the percentage has declined in developed nations due to mechanization.