Although the functionalist model was soon superseded, later "neofunctional" theorists adopted its approach by examining the ways that ritual regulated larger ecological systems. Roy Rappaport, for example, examined the way gift exchanges of pigs between tribal groups in Papua New Guinea maintained environmental balance between humans, available food (with pigs sharing the same foodstuffs as humans) and resource base. Rappaport concluded that ritual, "...helps to maintain an undegraded environment, limits fighting to frequencies which do not endanger the existence of regional population, adjusts man-land ratios, facilitates trade, distributes local surpluses of pig throughout the regional population in the form of pork, and assures people of high quality protein when they are most in need of it". Similarly, J. Stephen Lansing traced how the intricate calendar of Hindu Balinese rituals served to regulate the vast irrigation systems of Bali, ensuring the optimum distribution of water over the system while limiting disputes.