16 FORESTS OF THE HAWAIIAN ISLANDS. 



these slopes, at^elevations of 1,500 to 3,000 feet, where the niini'all is 

 greatest, is found the heaviest forest. Toward regions of lessened 

 exposure to trade winds and decreased rainfall the forest becomes 

 thinner and of poorer quality, and on the leeward, where the rainfall 

 is in places less than 30 or 40 inches per year, there was often no forest 

 at all. Probably the area which originally bore no forest because of 

 insufficient rainfall was quite large, for it is certain that all of the 

 important islands now have large tracts to which no trees of the native 

 forests are adapted. 



Elevation has put a sharp limit to the forest on the islands of 

 Hawaii and Maui at from 6,000 to 8,000 feet. This leaves very large 

 areas of Mauna Loa, Mauna Kea, Hualalai, and Haleakala devoid of 

 forest, and they have always been so. The mountains of the other 

 islands, being under 6,000 feet, are forested to their summits. Six to 

 eight thousand feet is a surprisingly low timber line, considering the 

 favorable conditions of soil, moisture, and temperature which prevail 

 at that altitude in Hawaii. The sufficient reason seems to be that the 

 species composing the native forests are all representatives of the torrid 

 zone, and in these islands, which lie right at the edge of the Tropics, 

 find their limit at the low altitude named. 



On the slopes of Mauna Loa lava flows have put a sharp limit to 

 the forest in a number of places. The flow of 1881, which ran from 

 near the top of the mountain almost to the sea, cut a wide swath 

 through a dense forest for fully 15 miles. Many previous flows had 

 resulted similar!} 7 , and while the forest is slowly replacing itself on 

 the older flows, hundreds of years are required for the lava to decom- 

 pose sufficiently to support a normal growth of forest. Many thou- 

 sand acres which once must have been well forested are now surfaced 

 with lava rock (pahoehoe), and support only a meager growth of fern 

 and stunted trees. Slowly this rock is decomposing, and as it decom- 

 poses the forest improves. 



RAPID DECADENCE OF THE FOREST. 



The above were the chief agencies restricting the forest up to about 

 one hundred years ago. Since that time various deleterious agents 

 have worked so effectually toward the destruction of the woodland 

 that every forest in the islands has been reduced, until it is now only a 

 fragment of what it was" originally. The island of Molokai well 

 illustrates this point. This island, 38 miles long by 8 miles wide, has 

 a range of mountains over 4,000 feet high at its eastern end, drops to 

 a low plain in the center, and rises to 1,380 feet near the western end. 

 Originally all the eastern end well down to the central plain, and the 

 highest part of the western end, were heavily forested. The plain 

 was park-like, with scattering groves of trees. There is little at pres- 

 ent even to indicate former conditions. All the western end is bare. 



