TREES THAT MAKE LAND — STEPHENS 495 



In this manner — and over many, many years — an island may be 

 formed on the leeward side of a coral reef. 



Similar results may be produced near the mouths of rivers. (Here 

 there are no corals, of course, for corals cannot live in brackish water.) 

 Mangroves become established along the shores of rivers and on shal- 

 low bars formed by sand and mud carried downstream by the cur- 

 rent and deposited at the mouth of the stream. Hundreds of man- 

 grove keys may be formed near the mouth of a single river. Over a 

 long period of time some of these keys may rise above the reach of 

 high tide, producing conditions for the growth of mahogany, oak, and 

 other hardwoods. A dense hammock may develop which may even- 

 tually become a part of the mainland. 



1,500 ACRES OF TREE-MADE LAND 



The land-building properties of mangroves are substantial in areas 

 such as south Florida, where sedimentation is great. During his 

 study of Florida mangroves, Dr. J. H. Davis found that about 1,500 

 acres of new land had been formed in Biscayne Bay and Florida Bay 

 over a period of 30 to 40 years. (For the purposes of this estimate, 

 Dr. Davis considered mangrove swamps to be land.) During this 

 study it was found that the soil of many inland hammocks in the 

 Everglades is composed largely of mangrove peat. 



One of the greatest mangrove forests in the Western Hemisphere — 

 and possibly in the entire world — is found in southwest Florida. Ex- 

 tending from the southern tip of the mainland up the Gulf coast to 

 Marco, the forest includes the area known as the Ten Thousand 

 Islands and the mouths of numerous rivers draining the Everglades. 

 The actual number of mangrove islands is unknown, since the islands 

 constantly merge and new ones are constantly born. Unlike the 

 low, twisting trees of most mangrove swamps, the trees in this forest 

 often grow straight and tall — near the mouth of the Shark River 

 are red mangroves 80 feet high — but occasionally a tremendous tree 

 extends almost horizontally for about 100 feet, its trunk supported 

 by hundreds of aerial roots. Such trees may have been blown down 

 in storms of many decades ago. Other trees, killed by hurricanes, 

 stand upright, stark and white, like bleached skeletons. 



Even the strongest winds rarely uproot the mangroves, but hur- 

 ricanes may shake the trees so violently that the bark peels off, ex- 

 posing the soft cambimn layers to salt spray and waves, quickly killing 

 the trees. The great storm of 1960, Hurricane Donna, killed thousands 

 of large mangroves in southwest Florida — trees that had withstood 

 dozens of previous hurricanes. 



Wlien observed from seaward a mature mangrove forest is like a 

 massive green wall. Up close, twisting waterways are seen between 

 the islands, often virtual tunnels with merging branches forming a 



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