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Scalesia cordata is a tree endemic to southern Isabela. Before the arrival of humans, it formed widespread forests that harboured a great diversity of plants, birds and associated invertebrates. However, its range has been drastically reduced to only a few sparse populations due to land clearing for agriculture in the past and current replacement by invasive species. Together with the Galapagos National Park Directorate, we are taking several management actions to prevent the local extinction of the remaining populations of Scalesia cordata and to facilitate its recovery. These measures include collecting seeds, growing seedlings in the nursery, controlling invasive plant species negatively impacting Scalesia cordata trees, and working with farmers and the Isabela community to raise awareness about this species, unique to Isabela. Galapagos has seen few extinctions of plant species; we do not want Scalesia cordata to be one of them.
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Project Assistant
Pedro Gómez, Project Assistant
Scalesia cordata is one of 15 species of the Galapagos endemic genus Scalesia (family: Asteraceae). Scalesia cordata is one of the three Scalesia species that grow into trees. The Scalesia cordata forests are associated with other endemic plant, bird and invertebrate species. If we lose Scalesia, we will also lose these unique species associated with Scalesia forests.
Figure 2. Young Scalesia cordata trees at the GNPD nursery, Isabela. Photo: A. Walentowitz
Scalesia cordata is restricted to the humid zone of the Sierra Negra and Cerro Azul volcanoes in southern Isabela where it used to form extensive forests covering a large area of approximately 17,300 ha. Deforestation of these forests started as early as 1906 and they were later drastically reduced due to land use change, fires and invasive species. Studies of the distribution of Scalesia cordata in 1997 showed that these forest remnants covered less than 10 ha. All of these remnants were found to be heavily invaded by guava in 2006 and 2009, and it was estimated that only 0.1% of the original forest remained.
Figure 3. Young and adult Scalesia cordata tree at the GNPD nursery, Isabela Photo: A. Walentowitz
In 2019, an expedition consisting of CDF and GNPD members, returned to 17 sites that had Scalesia cordata populations in 2002. Unfortunately, only two of these sites still had Scalesia cordata trees left and of 1075 trees recorded in 2002, only 28 trees remained in 2019. Thanks to increased search efforts, the team was able to locate additional trees at three new sites. However, no natural regeneration (young Scalesia plants) was observed at any of these sites. This is very alarming, since Scalesia cordata has a short life span (approximately 15 to 20 years) and could become extinct within the next decade, if there were no young Scalesia cordata replacing the dying trees. To make things worse, the remaining populations at Sierra Negra and Cerro Azul are currently heavily invaded by introduced plants, especially guava (Psidium guajava), Siam weed (Chromolaena odorata) and blackberry (Rubus niveus).
Figure 4. CDF and GNPD expedition in 2019 to search por Scalesia cordata populations. Photo: A. Walentowitz
Urgent action was needed and CDF and GNPD teamed up in this project to restore the remaining populations of Scalesia cordata and prevent its extinction through management actions. These include controlling invasive plant species, planting nursery-grown Scalesia cordata seedlings, and identifying invertebrates associated with Scalesia cordata. To do this, it is essential to locate the areas in southern Isabela where there are still adult Scalesia cordata trees, collect seeds from as many different populations as possible, grow seedlings in nurseries, and work together with farmers and the Isabela community to increase the restoration success.
Prevent the extinction of Scalesia cordata by conservation management actions on Isabela, Galapagos Islands
1. Determine and map the distribution of Scalesia cordata and invasive plant species on Isabela at known visited sites at Sierra Negra and Cerro Azul and search for new Scalesia cordata populations.
2. Restore Scalesia cordata populations at least at 9 sites with nursery-grown seedlings and control invasive species at these sites.
3. Promote the establishment of Scalesia cordata populations on at least 5 farms in the agricultural zone, where Scalesia cordata was formerly present.
4. Determine invertebrates that are associated with Scalesia cordata, with a focus on pollinating species.
When we started our field work on Isabela in August 2021, we thought that only about 300 adult Scalesia cordata trees were left in the wild. Luckily, through our work, we now know that this is not true. We have since been searching for new populations and have been monitoring the vegetation and invertebrates associated with Scalesia cordata at five sites (Cerro Grande, El Limon, Caleta Iguana, Velasco and Km 9). At the same time, we have been collecting seeds from all trees encountered. Thanks to our field and nursery technician from Isabela, Pedro Gómez, and the GNPD rangers, we identified three new sites with Scalesia cordata populations. Pedro, park rangers and field assistants are continuously controlling invasive plant species that inhibit the natural regeneration of Scalesia cordata.
Figure 5. CDF and GNPD expedition in 2021 to search por Scalesia cordata populations. Photo: H. Jäger
Carolina Carrión, our geospatial analyst, has conducted many hours of drone flights in the Galapagos National Park areas to confirm known Scalesia cordata populations and find new ones. At Cerro Grande, Carolina was able to identify more than 300 trees. After initial control of invasive plant species, more than 150 seedlings emerged, an amazing natural regeneration not observed at this site for years. Currently, dozens of Scalesia cordata seedlings from different sites are growing at the GNPD nursery on Isabela and their growth rate is being measured. This species grows very quickly, up to 30 cm in just two weeks.
Figure 6. Monitoring of permanent Scalesia cordata plots. Photo: A. Walentowitz
To obtain a better idea about the knowledge of Scalesia cordata in the local community, our CDF liaison officer on Isabela, Ernesto Bustamante, interviewed 20 farmers interested in the conservation of the species. Based on this information, we identified three farms where Scalesia cordata trees are currently present and two more farms that had Scalesia cordata trees in the past. So far, we have sampled invertebrates at these farms, and samples are currently being identified by our entomologists Jacqueline Rodríguez and Julia Bolaños.
Figure 7. Flying the drone to search for new Scalesia cordata populations. Photo:A. Walentowitz
Finally, we are conducting activities to raise public awareness of Scalesia cordata and the project among park rangers, naturalist guides and the Isabela community in general, because without their support and interest, this species could disappear within our generation.
Keywords: Endemic tree, threatened species, Isabela island, Asteraceae
- Delgado P. 1997. Distribución de Scalesia cordata, su interacción con Psidium guajava y biología reproductiva, Isabela Sur, Galápagos. Tesis de Licenciatura. Pontifíca Universidad Católica del Ecuador, Quito, Ecuador.
- de Vries T, Tupiza A. 1990. The dynamics of Scalesia cordata (Asteraceae) in different habitats in Sierra Negra, Isabela, Galápagos. In: Lawesson JE, Hamann O, Rogers G (eds.) Botanical research and management in Galápagos. Monographs in Systematic Botany from the Missouri Botanical Garden 32: 137-147.
- Eliasson U. 1984. Native climate forests. In: Perry R (Eds.). Key environments Galapagos. Pergamon Press, Oxford, UK, 101-114.
- Jaramillo P., Chávez J. 2002. Evaluación y estado actual de Scalesia cordata Stewart en el volcán Sierra Negra, Isla Isabela, Galápagos. Technical Report at the Charles Darwin Foundation.