Effects of cattle grazing on the mountain parkland ecosystem, Mauna Loa, Hawaii

Abstract

The objective of this investigation is to determine the effects that cattle have had on vegetation and soils of the mountain parkland ecosystem of Mauna Loa on the island of Hawai'i. A portion of this ecosystem is contained within Hawaii Volcanoes National Park and has been protected from cattle grazing since 1948. The mountain parkland ecosystem extends from the Park into neighboring ranchlands, where cattle grazing continues. In this study, grass and shrub communities of this ecosystem in the Park were compared with corresponding communities of the adjacent ranch. Differences in vegetation and species composition were quantified, and various soil parameters were examined to determine whether edaphic factors differed in the two areas. As the Hawaiian Islands support no indigenous mammal species other than the hoary bat (Lasiurus cinereus) and the monk seal Monachus schauinslandi (Tomich 1969), the mountain parkland ecosystem and all other Hawaiian land ecosystems evolved in the absence of large herbivores (plant-eating animals). Thus the Hawaiian flora has not undergone selection for resistance to herbivory. The introduction of large mammals began at the end of the 19th century and has included cattle (BOS taurus), sheep (Ovis aries and 0. musimon), goats (Capra hircus), deer (Axis axis and Odocoileus hemionus), and pigs (Sus scrofa). The purpose of this literature review is to ascertain how cattle and other large mammalian herbivores have affected natural vegetation in various parts of the world. Ecosystems with indigenous mammalian herbivores and those which have evolved in the absence of large animals are considered for the purpose of determining whether the two types of ecosystems are differently affected by herbivores. These examples of herbivory in other parts of the world may lend insight to the impact of introduced animals in the mountain parkland of Mauna Loa as well as in other parts of the Hawaiian Islands.