WEST 45 



salt or brackish water occurs at high tide. (3) The fresh-water swamp , which is flooded by 

 fresh to slightly brackish water from rivers during high tide. One-half to two miles wide, the 

 vegetation of this zone is comprised of the giant nato tree ( Mora megistoperma ) and clumps of 

 the naidi palm ( Euterpe , sp.), highly reminiscent of the nipa palm association of Southeast Asia. 

 (4) On slightly higher ground immediately inland from the alluvial areas affected by tide, begins 

 the fourth zone— the vast equatorial rainforest that covers the rest of the coastal and western 

 slopes of the Andes to an elevation of four to five thousand feet. 



This peculiar zonation of vegetation appears to be typical of most mangrove coasts of the 

 world. It is described for the Malaya Peninsula by Watson^ and by Dobby,^ for the west coast 

 of Africa by Grewe,^ and for the Guiana coasts of northern South America by Martyn.'^ Further 

 field work is necessary to ascertain the actual distribution of this zonation along other man- 

 grove coasts. 



With the gradual extension of the coast seaward through deposition, there seems to be a 

 slow successional change within the vegetation zones. As the floor of the fresh-water swamp 

 becomes higher and better drained, equatorial rainforest plants Invade; eventually fresh-water 

 swamp plants encroach upon the landward margin of the mangrove. In turn, mangrove succeeds 

 the beach associations as the beaches become remnants cut off from the ocean front by forma- 

 tion of new strands and buried by tidal muds. Finally, the beach plants colonize newly deposited 

 stretches of sand along the ocean front. 



THE BEACH ZONE 



The beaches are made up of fine, compact sand, sorted from the river load by wave ac- 

 tion and distributed up and down the coast by longshore currents. Many beaches are five to 

 six miles long. Their width varies from 100 to 400 yards at low tide to zero to 25 yards at high 

 tide. They are smooth and firm and could support heavy motor vehicles. Some beaches, how- 

 ever, are crossed by rivulets, whose beds are often composed of quicksand. Fresh to slightly 

 brackish water can usually be found on the beaches by digging a few feet below the surface. 

 Moreover, tidal ponds, called pozos , form in slight depressions and shallow lagoons on the 

 landward side of beaches. At low tide these ponds afford an abundant supply of fish which na- 

 tives catch by spearing or by poisoning. Small fishing villages often occur at the end of beaches 

 near the mouths of estuaries or rivers. Groves of coconuts, small patches of maize and manioc 

 are often cultivated in the sandy soil of beach ridges near the villages. In terms of travel and 

 living, the beach zone appears to be the most favorable of those along the mangrove coast. 



Beach formation has been one of the major factors in the seaward extension of the low 

 coastal plain. Remnants of beach ridges separated by mangrove-enclosed lagoons occur in 

 abundance back of the present beaches. Due probably to slight sinking and alluviation, the beach 

 ridge zone is invaded by mangrove and eventually becomes part of the swamp. 



THE MANGROVE SWAMP 



This zone presents the most difficult problems in terms of travel and subsistence. The 

 most conspicuous tree of the swamp is the giant red mangrove (Rhizophora brevistyla) which 



Watson, J. D., "Mangrove Forests of the Malay Peninsula," Malayan Forest Records, No. 6, 

 pp. 1-275. 1928. 



^Dobby, E. H. G.; "Southeast Asia," p. 67, London, 1950. 



^Grewe, F., "Africanische Mangrovelandschaften. Verbreitung und wirtschaftsgeographische 

 Bedeutung," Wiss. Veroff. d. Deut. Mus. f. Landerkunde zu Leipzig , N. F. 9, pp. 103-177, 1941 . 



^Martyn, E. B., "A Note on the Foreshore Vegetation in the Neighborhood of Georgetown, Brit- 

 ish Guiana," Journal of Ecology, Vol. 22, p. 293, 1934. 



