One of the most destructive natural disasters is the volcanic eruption, the red hot lava destroys all it comes into contact with, no living thing in its path will survive. Yet volcanic islands can have some of the richest and most diverse floras in the ivorld and in Italy some of the richest farm land is on the slopes of Mount Vesuvius. Hawaii is hundreds of miles from the nearest land, and yet this volcanic island has a very rich and varied flora.
By studying the plant colonization of volcanic lava here it was seen that no decomposition of the rock to form soil is necessary before plant growth becomes possible. As it cools the lava forms a hard porous rock which is rich in various minerals, especially phosphorus, and is capable of holding sufficient water to allow plant growth. On Hawaii, Koua, one of the largest forests, grows on a minimum of soil on relatively uudecomposed lava flows.
Hawaii is so far from the nearest land that it is highly unlikely that even thoseadapted for wind dispersal were carried this far by the wind. Most seeds were probably brought here originally by birds, but all species will have arrived through necessity by long distance dispersal. In fact as many as 50 species are known to have come from North America.
Some of the first species to have arrived will have been those with small fleshy fruits, such as Vaccinium, which are popular with birds. The birds eat the fruit before migration and deposit the in their excretion on the lava. Other early colonizers would have been ferns, their small light spores easily catching in the mud on the birds’ feathers and feet.
may arrive by various methods. The largest single-seed fruits, such as the coconut, are capable oj floating in sea water for some considerable time before they may be washed up on an island’s shore. Other seeds may float on rafts or drift wood.
Such a fertile substrate as a lava flow will not long he without vegetation wherever it is situated. Even in the very arid Galapagos Islands a few plants grow on pure lava, including the endemic , Brachycereus nesioticus.