New York Times - 5/30/08
Rising prices of synthetic fertilizers and organic foods have intensified the collection of bird droppings on 20 climatically ideal islands off the coast of Peru where 12-inch-thick seabird guano coats the land. In the 19th century, Spain fought with Peru on the high seas for the right to mine the guano, which at that time was 150 feet high in places. Said an official of the Peruvian company that controls guano production (to a New York Times reporter in May), "Before there was oil, there was guano, so of course we fought wars over it." The exceptionally dry climate means that 12,000 to 15,000 tons of guano are available yearly.