The practice of agriculture is also known as "farming". Scientists, inventors, and others devoted to improving farming methods and implements are also said to be engaged in agriculture. 1 in 3 people worldwide are employed in agriculture, yet it only contributes 3% to global GDP. In 2017, on average, agriculture contributes 4% of national GDPs. Global agricultural production is responsible for between 14 and 28% of global greenhouse gas emissions, making it one of the largest contributors to global warming, in large part due to conventional agricultural practices, including nitrogen fertilizers and poor land management.