Tepuis forests
Tepuis forests are unique ecosystems located in southern Venezuela, as well as parts of western Guyana, northern Brazil, and eastern Colombia. Characterized by dramatic table mountains known as tepuis, these landscapes rise between 3,281 and 9,843 feet above the surrounding lowland forests and savannas. The term "tepui" means "house of the gods" in the Pemón language, reflecting the cultural significance of these formations. The tepuis host a remarkable range of biodiversity, with over 2,000 plant species, many of which are endemic, meaning they are found nowhere else on Earth. This diversity arises from the isolated environments atop the tepuis, where unique climatic conditions create distinct plant communities, including evergreen rainforests and cloud forests.
While relatively untouched due to their inaccessibility, the tepuis face increasing threats from human activities such as illegal mining, logging, and tourism, which can disrupt these delicate ecosystems. Climate change is also predicted to have a significant negative impact, with studies suggesting that a large percentage of the flora could become extinct by the end of the century. Conservation efforts are underway, with various protections established in Venezuela, where many tepuis are designated as national parks or natural monuments. However, challenges remain in enforcement and funding, particularly in neighboring countries. Overall, tepuis forests represent a critical and fragile component of South America's natural heritage.
Tepuis forests
Category: Forest Biomes.
Geographic Location: South America.
Summary: The dramatic sandstone mesas that tower over the lowland forests and savannas of southern Venezuela and its neighbors served as the inspiration for Sir Arthur Conan Doyle’s The Lost World.
In southern Venezuela, and to a lesser extent in western Guyana, northern Brazil, and eastern Colombia, more than 100 dramatic table mountains called tepuis rise 3,281–9,843 feet (1,000–3,000 meters) above the lowland forests and savannas. These mountains generally have flat tops and nearly vertical walls interspersed with talus slopes. Many of the tepuis are virtually inaccessible by foot. The word tepui comes from the Pemón people and means house of the gods.
While the tepuis used to form a contiguous landmass, they have long since been separated from one another. The environment on the summits of the tepuis can be very different from that of the lowlands. Due to the combination of extended isolation and climate differences, the tepuis summits have truly unique flora and fauna.
Reports of expeditions to this remote region in the 19th century served as the inspiration for Sir Arthur Conan Doyle’s novel The Lost World. In spite of such occasional publicity, its remoteness has helped maintain this ecoregion relatively intact.
The Guayana Shield, on which the tepuis rest, consists of a rock basement that began to form 1.8 billion years ago. Most of this rock basement was overlain with sediment, which was subsequently compressed and cemented together to form a thick layer of quartzitic and sandstone rocks. Uplifting broke this sandstone layer apart, and erosion resulted in the separation and isolation of the tepuis.
Tepui soils are generally sandy and poor in nutrients. Weathering has carved deep canyons, gorges, and sinkholes in the tepui summits. The tepuis are some of the oldest geological formations in all of South America. Pico da Neblina in Brazil, at 9,888 feet (3,014 meters), is the tallest tepui. Angel Falls, dropping from the broadest, 270-square-mile (700-square-kilometer) Auyantepui in Venezuela, is the world’s tallest waterfall at 3,212 feet (979 meters).
Because the ecoregion is located just north of the Equator, variations in climate are mainly due to the effects of the trade winds and differences in elevation. Rainfall is distributed evenly though the year, 79–94 inches (2,000–2,400 millimeters) on average. The average annual temperature is approximately 75 degrees F (24 degrees C) but can vary considerably with elevation. At the tops of the tallest tepuis, temperatures can drop to 32 degrees F (0 degrees C). The summits also differ from the lowlands in that they experience intense light and strong winds.
Zoned Biota
The vegetation of the tepuis changes with elevation, and both evergreen rainforests and cloud forest are found upon the tepuis. Generally, the plant communities found at the base, along the talus slopes, on the cliff walls, and on the summit are each distinct. Lowland species associated with the highland savanna or evergreen rainforest that surround the tepuis can be found at elevations below 1,640 feet (500 meters).
Cloud forest occurs on the talus slopes above 1,640 feet (500 meters) elevation. The bare sandstone of the cliff walls is home to plants that are adapted to grow in crevices, such as bromeliads (the pineapple family). The summits are home to a mixture of elfin forest, scrub, savanna, and bog adapted to withstand the intense environment.
The tepuis have exceptionally high plant diversity; more than 2,000 species of plants are known here. Approximately one-third of the species, and nearly 80 genera are endemic (found nowhere else) to the ecoregion. The highest concentrations of endemic species are found on the summits. Some summit endemics occur on most or all mountains, while others are highly localized, occurring on a single summit. Many carnivorous plants are found among the tepuis, possibly because the soil is so nutrient-poor.
The tepuis are home to almost 200 species of mammals. Many species’ natural distribution is confined to the Tepuis Forests ecoregion or the wider region of Amazonia. Nine species of primates and five species of cats live in the Tepuis Forests biome.
More than 600 species of birds have been observed here, including 41 endemic bird species. Likewise, more than 150 species of reptiles and amphibians have been recorded for this ecoregion, including venomous snakes such as fer-de-lances, coral snakes, and bushmasters.
Effects of Human Activity
The lowlands surrounding the tepuis are sparsely populated, and the tepuis themselves are difficult to access. As a consequence, much of this ecoregion has remained relatively untouched. However, anthropogenic disturbances are on the rise. These disturbances include the setting of accidental and deliberate fires, logging, over-collecting of flora and fauna, and illegal mining for gold, diamonds, and bauxite.
Tourism is also having an effect, as visiting hikers litter, trample vegetation, and strip woody plants for firewood. Plants on the summits of tepuis are often adapted to the climate and the poor soils tend to support slow-growing types, making natural recovery from disturbance a protracted process. According to a 2017 study in the journal Frontiers in Plant Science, Climate change is having a significant negative effect on the flora of this ecoregion. The study predicts that 80 percent of the flora in the Neotropical Guayana Highlands could become extinct by 2100. This figure in-cludes about half of the endemic species of plants.
Conservation Efforts
Steps have been taken at national and international levels to conserve the Tepuis Forests biome, but the status of the conservation efforts varies by country. In Venezuela, all the tepuis above 2,625 feet (800 meters) are protected as natural monuments, national parks, or biosphere reserves. Canaima National Park is a UNESCO World Heritage Site. Commercial logging is prohibited in the Venezuelan state of Amazonas.
By contrast, legislation to establish a National Protected Areas System in Guyana was passed only in 2011. Even where protected areas have been established, they are often just “paper parks,” lacking infrastructure or funds. The vast sizes of the protected areas and their remoteness make enforcement of conservation regulations difficult.
Bibliography
Berry, P. E., B. K. Holst, and K. Yatskievych, eds. Flora of the Venezuelan Guayana. St. Louis, Missouri: Botanical Garden and Timber Press, 2003.
Hollowell, T. and R. P. Reynolds. “Checklist of the Terrestrial Vertebrates of the Guiana Shield.” Bulletin of the Biological Society of Washington 13 (2005).
Rull, Valentí, and Teresa Vegas-Vilarrúbia. “Potential Responses of Vascular Plants from the Pristine ‘Lost World’ of the Neotropical Guayana Highlands to Global Warming: Review and New Perspectives.” Frontiers in Plant Science, vol. 8, no. 81, 2017, doi: 10.3389/fpls.2017.00081. Accessed 30 Aug. 2022.
Zimmer, Carl. “It’s Not So Lonely at the Top: Tepui Ecosystems Thrive Up High.” New York Times, May 7, 2012.