Agriculture imposes negative externalities ( uncompensated costs) upon society through public land and other public resource use, biodiversity loss, erosion, pesticides, nutrient runoff, subsidized water usage, subsidy payments and assorted other problems. Positive externalities include self-reliance, entrepreneurship, respect for nature, and air quality. Organic methods reduce some of these costs. In 2000 uncompensated costs for 1996 reached 2, 343 million British pounds or £208 per ha ( £84.20/ac) .A study of practices in the USA published in 2005 concluded that cropland costs the economy approximately 5 to 16 billion dollars ( $30–96/ha - $12–39/ac) , while livestock production costs 714 million dollars.Both studies recommended reducing externalities. The 2000 review included reported pesticide poisonings but did not include speculative chronic health effects of pesticides, and the 2004 review relied on a 1992 estimate of the total impact of pesticides.