The Lake: Laguna Zoncho

Laguna Zoncho from hill top, partial view.

Laguna Zoncho (literally, Vulture Lake in English) has a unique history in the county and the country, as it is one of the most studied lakes in the world. Because of the history of habitation around the lake for much of 3200+ years, the Cántaros property–Sitio Zoncho or Sitio Cántaros–is cited as one of Costa Rica’s important archaeological sites but remains almost completely unexcavated. Small research digs around the lake by archeologists and other scientists have yielded interesting historical artifacts; and analysis of core samplings from the lake-floor sediment have added to the extensive knowledge about the history of land use on the property. The evidence is abundant that indigenous people were almost continuously occupying the lake basin for thousands of years until the time of the Spanish conquest.

Laguna Zoncho, view from south shore.

At 1190 m (3904 ft), the lake falls mainly within the tropical premontane rain forest life zone. While extensive forest of this type still exists at the nearby Las Cruces Biological Field Station, the Laguna Zoncho watershed and adjacent lands today are mainly in pasture and agriculture with only small patches of remnant and regenerated forest. Around the lakeshore can also be found pines, eucalyptus and other non-native species. A non-native aquatic weed that now covers much of the lake surface has been left alone for the fish and birds to use.

Formation. An unusual wetland with natural clay bowl (hence Finca Cántaros’ name, based on the old Spanish word cántaro or earthenware vessel), Laguna Zoncho formed as the result of an ancient geological slumping or damming behind slumped debris from a nearby hill.

Size, depth & rainfall. The area of this small lake is about .75 ha (1.85 acres) with a maximum depth of 2.3-4.3 m (7.5-14.1 ft) depending on the season. The lake seems to be fed entirely by rainwater from the immediate, bowl-shaped watershed; there are no streams or known springs. Climate data suggests mean annual rainfall of 3000-4000 mm (9.8-13.1 ft). Precipitation in this area is lowest from December to March. (There is now an overflow outlet pipe at the extreme western end of the lake to prevent flooding of the gardens and orchards at that end of the lake during the height of the rainy season.)

Archaeology and history. Laguna Zoncho is located within the Diquís subregion of the archaeological area known as Greater or Gran Chiriquí which comprises Southern Pacific Costa Rica and Western Panama. The Diquís represent the least known of the country’s three archaeological zones.

The presence of charcoal, maize pollen and artifact fragments in the core samples of lake sediments taken by paleoecologists, as well as artifacts excavated by archaeologists from the area near the lake, indicate near continuous human occupation of the lake basin for over 3200 years. The core sample evidence shows that forest clearing and burning by prehistoric agriculturists were most apparent between about 1240 BC to AD 1540. After this period of about 2780 years, the Laguna Zoncho area was largely abandoned, and the forest regenerated. Warfare among indigenous tribes, illness brought by Spanish explorers, fear of slavery, or effects of ash from an explosion of nearby Volcán Barú in Panama roughly 500 years ago may all have played a part in departure of most of the indigenous people from Laguna Zoncho. Only small-scale maize cultivation characterized the watershed from AD 1490 until the Italian settlement of San Vito in 1952.

When the Italians arrived in San Vito in the mid-1900s, they encountered a forest that was fairly empty, with a few recent and recovering agricultural clearings. Much of the landscape was covered in mature forest that looked “pristine” or “virgin” after as many as five centuries of regrowth. The colonists and other local settlers of that period were likely unaware that the landscape they were about to dramatically transform into large open tracts for agriculture (mostly coffee) and cattle grazing had once held much larger indigenous populations that had greatly changed landscapes in an earlier cycle of human use

Masked Ducks visit the Laguna most years, late January into May. Photo: © Marco Saborio

Wildlife. Two species of fish are found in the lake: the Wolf cichlid (Parachromis dovil, locally called Guapote), which can often be seen “grazing” in the weeds near the surface, and the much smaller and more elusive Banded tetra (Astyanax aneus or Golosa or Plateada in Spanish). Frogs (Craugastor crassidigitus, Rana taylori, Hyla ebracata, Eleutherodactylus fitzingeri, Eleutherodactylus ridens and other species) and turtles are also found in and around the lake. Diverse aquatic birds are protected here, including Common Moorhen year-round, and Purple Gallinule, White-throated Crake, Gray-necked Wood-Rails, Masked Ducks (late January to May), and occasional fishers such as Ringed Kingfisher, Osprey, Cormorants, and Great Blue and White Heron.

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Sources: Sally P. Horn and Rachel M. Clement, Pre-Columbian land-use history in Costa Rica: a 3000-year record of forest clearance, agriculture and fires from Laguna Zoncho [The Holocene 11,4 (2001) pp. 419-426]; etc.

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