In Hawaiian religion, the peaks of the island of Hawaiʻi are sacred. An ancient law allowed only high-ranking aliʻi to visit its peak. Ancient Hawaiians living on the slopes of Mauna Kea relied on its extensive forests for food, and quarried the dense volcano-glacial basalts on its flanks for tool production. When Europeans arrived in the late 18th century, settlers introduced cattle, sheep and game animals, many of which became feral and began to damage the volcano's ecological balance. Mauna Kea can be ecologically divided into three sections: an alpine climate at its summit, a Sophora chrysophylla-Myoporum sandwicense (or māmane-naio) forest on its flanks, and an Acacia koa-Metrosideros polymorpha (or koa-ʻōhiʻa) forest, now mostly cleared by the former sugar industry, at its base. In recent years, concern over the vulnerability of the native species has led to court cases that have forced the Hawaiʻi Department of Land and Natural Resources to eradicate all feral species on the volcano.