The United Nations Environment Programme (UNEP) representative said at the UN Framework Convention On Climate Change's 7TH Conference of Parties (COP-7) in Marrakech (Morocco) in November 2001, that the harvests of some of the world’s key food crops, such as wheat, rice and maize, could drop by up to 30% over the next 100 years, due to global warming.
Mradi wa Mazingira wa Umoja wa Mataifa (UNEP) kupitia mwakilishi wake kwenye mkutano wa saba juu ya mabadiliko ya Hali ya Hewa (COP7) uliofanyika Novemba 2001 Marakech nchini Morrocco ulielezea kwamba baadhi ya mazao muhimu ya kilimo, ikiwemo ngano, mpunga, na mahindi, huenda uzalishaji wake ukapungua kwa asilimia 30% kwa kipindi cha miaka mia moja ijayo kutokana na ongezeko la joto duniani.