farming, particularly factory farming, are environmentally unsustainable. According to a 2006 United Nations Food and Agriculture Organization report, Livestock's Long Shadow, around 26% of the planet's terrestrial surface is devoted to livestock grazing. The UN report also concluded that livestock farming (mostly of cows, chickens and pigs) affects the air, land, soil, water, biodiversity and climate change. Livestock consumed 1,174 million tonnes of food in 2002—including 7.6 million tonnes of fishmeal and 670 million tonnes of cereals, one-third of the global cereal harvest. Paul Watson of the Sea Shepherd Conservation Society called pigs and chicken "major aquatic predators", because livestock eat 40 percent of the fish that are caught. A 2010 UN report, Assessing the Environmental Impacts of Consumption and Production, argued that animal products "in general require more resources and cause higher emissions than plant-based alternatives". It proposed a move away from animal products to reduce environmental damage. A 2015 study determined that significant biodiversity loss can be attributed to the growing demand for meat, which is a significant driver of deforestation and habitat destruction, with species-rich habitats being converted to agriculture for livestock production. A 2017 study by the World Wildlife Fund found that 60% of biodiversity loss can be attributed to the vast scale of feed crop cultivation needed to rear tens of billions of farm animals, which puts an enormous strain on natural resources resulting in an extensive loss of lands and species. In November 2017, 15,364 world scientists signed a warning to humanity calling for, among other things, "promoting dietary shifts towards mostly plant-based foods". A 2018 study found that global adoption of plant-based diets would reduce agricultural land use by 76% (3.1 billion hectares, an area the size of Africa) and cut total global greenhouse gas emissions by 28%. Half of this emissions reduction came from avoided emissions from animal production including methane and nitrous oxide, and half came from trees re-growing on abandoned farmland which remove carbon dioxide from the air. The authors conclude that avoiding meat and diary is the "single biggest way" to reduce one's impact on Earth. The 2019 IPBES Global Assessment Report on Biodiversity and Ecosystem Services found that industrial agriculture and overfishing are the primary drivers of the extinction crisis, with the meat and dairy industries having a substantial impact. On 8 August 2019, the IPCC released a summary of the 2019 special report which asserted that a