There are also occasional earthquakes, like the one that rocked Anatahan in 1990, measuring 7.4 on the Richter scale. Most of the islands north of Saipan are part of the Northern Islands Sanctuary, uninhabited save for game wardens and the flora and fauna they preserve. The coconut palm tree is the most important plant in the islands. Copra, the dried meat of the nut from which coconut oil is made, is the commonwealth's most important export and a major source of revenue for many residents. The nut also provides food and drinking liquid, while the flowers provide sap for making a wine called tuba.
Rope is made from the green coconut husks, and fuel and charcoal are made from mature husks.
The wood is used for lumber and carving, the fronds for thatch and baskets. The islands' other main tree is the flame tree, which has scarlet blossoms. You'll also see coleus, caladium and philodendron. The only land mammals native to the islands are bats, though they've all but disappeared due to their popularity in Chamorro cuisine. Animals that have been introduced include dogs, cats, mice, rats, pigs, cattle, horses and goats.