Jul 30
2025

The famous inselberg “O Frage e a Freira“ (The Brother and the Nun) in the state of Espírto Santo in southern Brazil. According to legend, the two clergymen worked in missionary work among the indigenous people and fell in love.

Inselbergs are not mountains on islands in the sea, but rather mountains on land that protrude like islands from – usually tropical – regions. Numerous such isolated hills can be found in southern Brazil, not far from the Atlantic coast. The most famous example is Sugarloaf Mountain in Rio de Janeiro, which is now located within the city. Uluru (Ayers Rock) in Australia is also such a geological phenomenon.

An international team of researchers has now compiled an inventory of the plant species found on these mountains in southern Brazil. The goal was also to identify ways to restore nature to the former quarries there.

A key species for life in these extreme habitats is the kapok tree (Pseudobombax petropolitanum). Its roots hook into tiny cracks in the rock and help hold soil and other deposits on the rocks. In this way, they create microenvironments that favor the settlement of other species.

What many of them utilize is brought exclusively by wind or rain.

Growth in these ecosystems is usually only a few centimeters per year. Nevertheless, the researchers found surprisingly robust trees: They can “store up to 48 tons of carbon per hectare in aboveground biomass, similar to seasonal forests located in dry locations and with low productivity,“ the study states.

One special survivor is Wunderlichia azulensis. It belongs to the daisy family and grows exclusively on rocks. Like the kapok tree, it is an endangered species.

Sugarloaf Mountain in Rio de Janeiro is also an inselberg. This photo shows it from Guanabará Bay. Source: Arne Müseler / Wikimedia Commons

The research group, with members from Brazil and Canada, visited four inselbergs in the south of the state of Espírito Santo in the municipalities of Alegre, Cachoeiro de Itapemirim, Mimoso do Sul, and Muqui.

The vegetation on the inselbergs is forest-like and dominated by small trees, shrubs, and palm trees. However, in favorable urban locations, the researchers also found specimens with diameters of up to 116 centimeters and heights of 16 meters.

“Many of these plants are found only in these environments, and some are already threatened with extinction, primarily due to the expansion of natural stone extraction,“ warns Dayvid Couto, head of the study. The results were published in April 2025 in the Journal of Mountain Science.

At the end of the study, species are identified that could help restore damaged areas. This also concerns nature conservation beyond the inselbergs: They are often used by animals that value the fleshy fruits of other plants there as food.

Scientists from the Instituto Nacional da Mata Atlântica (INMA), the Universidade Federal de Minas Gerais (UFMG), the University of Québec at Chicoutimi (UQAC, Canada), and the Universidade Estadual do Norte Fluminense (UENF) participated in the study.

Journal of Mountain Science: “Woody vegetation on tropical inselbergs: floristic-structural characterization and aboveground carbon storage“