In 1913, engineers dammed the Chagres River to create Gatun Lake, a critical link in the newly built Panama Canal. As water filled the valley, it swallowed farmland and forest, but the highest hills refused to go under. One of them, a 15.6-square-kilometer hilltop carpeted in tropical forest, became an island in the middle of a man-made lake in the middle of a man-made waterway. That accidental island is now one of the most intensively studied patches of tropical forest on Earth, a living laboratory where scientists have spent more than a hundred years trying to understand how rainforests work.
Barro Colorado Island owes its existence to the Panama Canal. Before the dam, it was simply a forested hilltop in the Chagres River valley. When Gatun Lake rose around it, the surrounding lowlands vanished beneath freshwater, isolating the hilltop and everything living on it. The U.S. government designated the island a nature reserve on April 17, 1923, recognizing that the rising waters had inadvertently created something rare: a tropical forest fragment surrounded by a moat, accessible by boat but otherwise untouched. Initially the Panama Canal Company administered the island under the direction of entomologist James Zetek. By 1946, the Smithsonian Institution had taken over, combining the island with five adjacent peninsulas into the Barro Colorado Nature Monument.
The Smithsonian Tropical Research Institute maintains a permanent research station on the island, and the data collected there has shaped modern tropical ecology. A 50-hectare forest plot, established to track every tree with a trunk diameter of one centimeter or more, has been censused repeatedly over decades. Each census records which trees lived, which died, which seedlings appeared, and which species gained or lost ground. A sister plot at the Pasoh Forest Reserve in Malaysia, established in 1987, allows researchers to compare the dynamics of two tropical forests on opposite sides of the planet. The island has been designated an Important Bird Area by BirdLife International, and the biodiversity inventoried here includes howler monkeys, white-faced capuchins, anteaters, coatis, toucans, and thousands of insect species whose interactions form a web that scientists are still mapping.
Life on a research island follows its own rhythm. Scientists arrive by boat, usually from the town of Gamboa, and settle into a routine shaped by the forest's schedule rather than any human clock. Elizabeth Royte chronicled this world in her 2002 book The Tapir's Morning Bath, following researchers through their days of climbing trees, setting traps for beetles, tracking mammal movements, and arguing over data at the station's dining hall. The research here has influenced fields from plant physiology to animal behavior to climate science. Because the island has been studied continuously since the 1920s, its data sets span time periods that most tropical research stations can only envy. That continuity makes Barro Colorado a reference point, a baseline against which tropical forests elsewhere are measured.
Visitors can tour Barro Colorado Island, but only by arrangement with the Smithsonian Tropical Research Institute. Tours include a boat ride across Gatun Lake, a guided two-to-three-hour hike through the forest, lunch, and a visit to the island's museum. The regulated access keeps foot traffic light and the forest largely undisturbed. U.S. federal law once stipulated that the island's natural features should be left in their natural state for scientific observation, with an exception only for declared national emergencies. That statute became moot in 1979 when the Canal Zone reverted to Panamanian sovereignty, but the protective ethos persists under Panamanian stewardship and Smithsonian management. The moat of Gatun Lake, the same water that created the island, continues to serve as its most effective boundary.
Barro Colorado Island sits at approximately 9.15N, 79.85W in Gatun Lake, the large freshwater body visible at the center of the Panama Canal. From 3,000-5,000 feet AGL, the island appears as a densely forested landmass surrounded by the lake's open water, clearly distinguishable from the surrounding peninsulas. The Panama Canal's shipping channel passes nearby. Marcos A. Gelabert International Airport (MPMG) at Panama City Albrook is the nearest major airfield. Expect tropical humidity, frequent afternoon thunderstorms, and haze reducing visibility over the lake.