Flora of Barro Colorado Island

   

Barro Colorado is an island in the Panama Canal Zone lying midway between the Atlantic and Pacific Oceans (9° 09'N, 79°51' W). At about 15.6 km2 (6 square miles), BCI is the largest island in Gatun Lake, the lake formed between 1911 and 1914 by the damming of the Rio Chagres to form the Canal. Gatun Lake, by far the largest expanse of water in the Canal, covers 420 km2 (164 square miles) at an elevation of about 25 m (85 feet) above sea level. The ship channel traversing the lake passes along the eastern and northeastern shores of the island, and waves from the passing ships cause substantial erosion along parts of these shores, especially during the dry season, when the trade winds are more forceful. 

BCI was set aside as a biological preserve in 1923 and is currently supervised by the Smithsonian Tropical Research Institute, which operates a modern field station at the Laboratory Clearing, on the northeast shore. Aside from this modest little settlement, there is very little that interrupts the dense forest cover: a dozen-odd smaller clearings, some of them used for navigational beacons; a network of trails crossing most of the island; a scattering of tree falls; a few shoreline marshes and silted coves; and an occasional ravine or streambed. And except for a small plateau in the west-central part of the island, the terrain is hilly, the hills dissected by ravines and generally well-drained slopes. The highest point, the Tower Clearing, is 165 m (538 feet) above sea level, 140 m (453 feet) above the level of the lake. 

The shoreline, deeply dissected by coves over much of its extent, is altogether about 65 km (40 miles) long, including the shores of its associated islands. The principal island associated with BCI (see the map on the endsheets) is Orchid Island, which is separated from Gross Point by a very narrow passage. Others that are considered part of the biological preserve are Slothia Isle, in Laboratory Bay; Ormosia Isle, near the Front Lighthouse Clearing; and Sal and Pimiento Islands, a pair of small islands northeast of Fairchild Point. 

Dedication

To Patricia,
Whose skilled assistance contributed to every phase of this work.