Sao Tome Flora & Plant Diversity of Príncipe Island

Príncipe Island is recognized globally as a biodiversity hotspot and Plant Diversity Center, largely due to exceptional flora and remarkable endemism levels. The island, oldest in the archipelago, resulted from volcanic activity along the Cameroon volcanic line approximately 31 million years ago. This extreme geographical isolation produced a high degree of terrestrial flora and fauna endemism that makes Príncipe botanically significant far beyond its tiny size.

For botanists, naturalists, and plant enthusiasts, Príncipe offers extraordinary opportunities to observe unique species found nowhere else on Earth. The nearly completely forested landscape and humid tropical climate create ideal conditions for plant diversity, with every forest walk revealing botanical treasures from endemic orchids to ancient tree ferns that have persisted for millions of years.

Flora Overview

Endemism & Taxonomic Diversity

Príncipe Island exhibits exceptionally high endemism rates. The estimated number of floristic species in São Tomé and Príncipe is approximately 1,200, of which about 960 are native. While the 2012 Biosphere Reserve application identified 450 flora species with 24 endemics, more recent estimates indicate 58 endemic species exist only on Príncipe. The total endemic taxa for the archipelago reaches 119 (107 species and 12 infraspecific taxa).

Dominant Families: The richest families in terms of taxa are Orchidaceae (orchids), Rubiaceae, and Euphorbiaceae (or Phyllanthaceae and Euphorbiaceae sensu stricto following taxonomic revision). These three families characterize the flora and include most endemic taxa, making them focal groups for botanical observation and conservation.

Orchidaceae: The most important plant family on Príncipe in terms of species number and abundance, presenting the highest endemism level. Príncipe harbors 64 orchid taxa, with 35 endemic species across the archipelago. For orchid enthusiasts, this concentration creates exceptional observation opportunities, with endemic species ranging from tiny epiphytes requiring magnification to appreciate to large, showy species visible from trail distances.

Pteridophytes (Ferns): The pteridophyte flora (ferns, clubmosses, and allies) is considered particularly rich. Príncipe hosts 75 pteridophytes distributed across 28 families, including ancient lineages that provide living connections to Earth's botanical past. These primitive vascular plants, predating flowering plants by millions of years, thrive in Príncipe's humid forests where moisture and shade create ideal conditions.

Vegetation Structure & Types

Príncipe's vegetation structure has been profoundly altered by colonization, creating a mosaic of native and secondary forest with varying conservation value.

Forest Cover

The area covered by forest in the Autonomous Region of Príncipe (RAP) approaches 95% of total island area—an extraordinarily high proportion that makes Príncipe one of Africa's most densely forested territories.

Secondary Forest (Capoeira): The vast majority of the island is covered by secondary forests, locally known as capoeira, resulting from regeneration following agricultural abandonment after 1975 independence. These secondary forests are filled with introduced species (297 taxa) alongside native regeneration, creating complex vegetation assemblages that support some endemic species while lacking the full diversity of primary forest.

Native Forest: Native forest (27% of terrestrial cover) refers to relatively undisturbed areas that were never completely cleared. These areas remain where climate and terrain conditions proved too adverse for profitable agriculture—typically steep slopes, high elevations, and the wettest zones where cultivation was impractical even during peak plantation era. For botanical observation, accessing these native forest remnants is essential to encounter the most sensitive endemic species.

Geographic Distribution

Northern Zone: Characterized by semi-humid secondary forest, mostly degraded, with plants including Pentaclethra macrophylla (locally called Muandim), which forms extensive stands in disturbed areas.

Southern & Central Zones: Harbor three vegetation types, two considered nearly intact—these represent Príncipe's botanical crown jewels where the highest endemic concentrations and most pristine forest conditions persist.

Montane Forest (Pico do Príncipe): The island summit (948m) and submontane forest around 600m constitute an area of exceptional conservation importance harboring unique flora with many species not yet scientifically identified. This cloud forest zone, perpetually shrouded in mist, supports specialized plant communities adapted to constant moisture and cooler temperatures—conditions found nowhere else on the island.

Coastal Formations

Coastal formations include mangroves, generally very small, composed of species like Rhizophora racemosa and Avicennia germinans. These limited mangrove stands occur in protected bays where freshwater meets saltwater, creating brackish conditions suitable for these specialized halophytic trees. The island lacks savanna formations, with forest extending virtually to sea level except where human settlement has created clearings.

Notable Endemic Species

Knowledge of Príncipe's flora has expanded through recent projects, resulting in identification of 8 new tree species to science and assessment of conservation status for rare species. Many tree and herbaceous species are Critically Endangered (CR) or Endangered (EN) due to historical habitat destruction and current threats including ecotourism pressure and small-scale agriculture.

Critically Endangered & Endangered Endemics

Strephonema sp. nov. (Undescribed tree species awaiting publication) — Status: Critically Endangered (CR). Threatened by agricultural activities and timber cutting. Restricted to mature lowland forest near Rio Porco, Barriga Branca, and on trails within PNP. This species' delayed formal description highlights how recently Príncipe's flora has received systematic scientific attention.

Tree Fern (Alsophila camerooniana var. currorii) — Status: Critically Endangered (CR). Threatened by historical habitat destruction for plantations. Endemic to Príncipe Island, found in lowland forest (60-350m elevation). These impressive tree ferns, with trunks reaching several meters height, represent ancient plant lineages and create distinctive understory structure in mature forest.

Tarenna principensis (Rubiaceae tree) — Status: Endangered (EN). Threatened by ecotourism on Pico Papagaio trail and small-scale agriculture. Central-southern island. Occurrences on Pico do Príncipe, Oquê Pipi, and Pico Papagaio, mostly within PNP. This species demonstrates how even well-intentioned ecotourism can threaten endemic plants through trail erosion and trampling.

Chrysophyllum calophyllum (Sapotaceae shrub) — Status: Endangered (EN). Threatened by ecotourism on Pico Papagaio. Found in low vegetation on summits between 404-602m elevation. Known from Pico Papagaio and Pico Mesa. Summit specialists like this shrub face concentrated threats as hiking becomes increasingly popular.

Pauridiantha principensis (Rubiaceae) — Status: Endangered (EN). Threatened by tourism (Pico do Príncipe) and illegal hunting (Morro de Leste). Known from only two occurrences on Pico do Príncipe and Caminho do Morro de Leste. This extremely restricted distribution makes the species vulnerable to any localized disturbance.

Impatiens manteroana (Balsaminaceae herb) — Status: Endangered (EN). Threatened by tourist activities and agricultural expansion. Endemic to Príncipe. Grows in dense humid forest among wet, shaded rocks. This delicate herb demonstrates how ground-layer plants suffer from foot traffic on informal trails.

Begonia fusialata var. principensis (Begoniaceae herb) — Status: Critically Endangered (CR). Threatened by stone quarries, house construction, and cocoa agriculture in Porto Real. Endemic to Príncipe. Found on humid rocks in partial shade below 200m elevation. This lowland endemic faces multiple threats in accessible areas subject to development pressure.

Diaphananthe principensis (Undescribed orchid species) — Collected in 2017, representing a large new endemic orchid species. IUCN conservation status not yet published. For orchid enthusiasts, this recent discovery suggests additional endemic species await discovery by attentive observers.

Historical Context & Research

Colonial-Era Botany

The first botanical surveys of the archipelago date to the colonial period. The most complete vegetation list was prepared by Arthur Exell (1944, 1956), who conducted detailed sampling on the islands in 1932-1933. Exell's Catalogue of the vascular plants of S. Tomé (with Príncipe and Annobon) (1944) remains a historical reference, though modern taxonomy has revised many classifications and added numerous species.

Botanical studies also collected information on plants with medicinal and industrial uses, documenting traditional knowledge that risks being lost as younger generations adopt modern medicine. Roça Paciência, for example, cultivates aromatic herbs and medicinal plants, maintaining this ethnobotanical heritage.

Contemporary Research

Since 2016, projects have been underway to describe tree diversity on Príncipe Island. Fundação Príncipe and partners including Fauna & Flora International (FFI) and Missouri Botanical Garden have trained local technicians and conducted over 30 research expeditions on the island. The Understanding the Remarkable Biodiversity of Príncipe Island project (2019) resulted in 6 new species to science (mollusks) and 2 new records.

Recent projects also focus on reconstructing Príncipe's environmental history through sediment core analysis, understanding historical flora distribution and how vegetation responded to climate changes and human impacts over millennia. This paleobotanical work provides context for current conservation by revealing which ecosystems have persisted longest and merit priority protection.

Researchers like T. Stévart have led Orchidaceae taxonomy and conservation, publishing new Red List assessments for 106 São Tomé and Príncipe species. This systematic evaluation provides the data foundation necessary for evidence-based conservation planning.

For Plant Enthusiasts

Observation Opportunities

Serious botanists should allocate substantial time for forest exploration with knowledgeable guides who can identify endemic species and explain ecological relationships. The highest plant diversity and endemism concentration occurs in PNP's southern native forest, particularly montane zones around Pico do Príncipe and submontane forest at 600m elevation.

Orchid enthusiasts should visit during wet season (October-May) when flowering peaks, though species bloom year-round. Many orchids are epiphytic, growing on tree branches and trunks at various heights requiring careful scanning of the canopy. Bringing binoculars aids identification of canopy species without disturbing them.

Photography Ethics

Never pick flowers, damage plants for better photographs, or collect specimens without proper permits. Endemic plants facing extinction cannot afford additional stress from well-meaning but destructive visitors. Photograph in situ using macro lenses and natural light rather than manipulating plants.

Contributing to Science

Report interesting plant observations to guides, who can relay information to Fundação Príncipe. Photographs of unusual species, particularly orchids and herbs, may document undescribed species or range extensions for known endemics. Citizen science observations contribute valuable data for conservation planning.

Supporting Conservation

Choose accommodations and tour operators committed to conservation, minimizing off-trail hiking that damages ground-layer vegetation. Stay on established trails even when tempting shortcuts appear—erosion from informal trails threatens endemic plants more than any single visitor realizes.

Botanical Significance

Príncipe's flora represents 31 million years of isolated evolution producing botanical treasures found nowhere else. The concentration of endemic orchids, ancient tree ferns, and undescribed species makes every forest hectare botanically significant. For plant enthusiasts, Príncipe offers experiences increasingly rare globally: encountering species known to science from only a handful of herbarium specimens, observing plant communities that have persisted largely unchanged for millennia, and contributing through responsible observation to conservation of irreplaceable botanical heritage.

The island's nearly complete forest cover—95% of territory—demonstrates that conservation and human communities can coexist when development follows sustainable models. Príncipe's botanical wealth survives because previous generations preserved forests. Whether future generations inherit this living library depends on choices made today by policymakers, communities, and visitors whose cumulative impacts determine whether endemic species persist or join the growing list of extinct species known only from pressed specimens in museum collections.