To the northeast of Santa Cruz Island within the Galapagos archipelago lies Plaza Sur, a small island made up of 13 hectares of land. It is the home to extraordinary fauna and flora, including the Opuntia echios var. echios species, most commonly known as the cactus (DPNG, 2014) (Jaramillo. et al 2017).
The scenario in Plaza Sur is that of ecological instability due to several factors arising from the introduction of foreign species, extreme weather phenomena such as El Niño, and variations in population sizes between predators and prey. Moreover, the drastic reduction of the O. echios var. echios population due to a lack of recruitment in the last 15 years has resulted in a fragile ecosystem (Snell et al., 1994; Sulloway, 2015; Sulloway et al., 2013). In light of the current situation, it calls for conservation actions that will ensure the survival of the Opuntia population and restore the natural balance of the Island.
The Galapagos Verde 2050 project (GV2015) part of the Charles Darwin Foundation (CDF), which aims to lead the restoration of degraded ecosystems on the Galapagos archipelago, selected the island of Plaza Sur as a test site. Here the team employed water-saving technologies (Groasis water-collecting plant pots), that not only provide the plants with a continuous water source and facilitate rapid plant growth (Jaramillo et al., 2017), but, it was also noted, the technologies that facilitated the survival of the seedlings under the predation pressure of land iguanas — as mentioned by Dr. J. Gibbs, one of the scientific collaborators.
As starting point, Opuntia seeds were collected from fruits and excrement and then germinated. The seedlings were transported to the island, where 595 were planted in three study sites (Jaramillo et al., 2017) (Flores ,D. 2017).
With the continuous monitoring program, it was possible to observe the growth and survival rate of the Opuntias, which up until July 2017 has reported the survival of 451 seedlings. Each monitoring involved the collection of biological and ecological data such as height, condition, and number of flowers per plant.
As part of the monitoring process, the Groasis Waterboxes were refilled with 15-20 liters of water.
Finally, protective meshes are replaced to avoid the predation of the Opuntia seedlings by the land iguanas. The meshes are replaced every 6 to 7 months approximately because the island has a very low altitude and so is easily effected by corrosive seawater.
In addition to the monitoring mortality in some of the Opuntias restored in the island (G. Morejón and P. Jaramillo per. commens), a sub-project was initiated with help of the entomology team at CDF to analyze the mesofauna present in Plaza Sur; for this analysis, pitfalls and Berles traps were set and soil samples were collected in order to capture the invertebrates present in different substrates.
DPNG (2014). “Plan de Manejo de las Áreas Protegidas de Galápagos para el Buen Vivir,” Dirección del Parque Nacional Galápagos, Puerto Ayora-Galápagos.
Jaramillo, P., Tapia, W., and Gibbs, J. (2017). “Plan de acción para la restauración ecológica de las islas Baltra y Plaza Sur. .” Fundación Charles Darwin y Parque Nacional Galápagos, Puerto Ayora.
Snell, H., Snell, H., and Stone, P. (1994). “Acelerada mortalidad de Opuntia en la isla Plaza Sur: ¿Otra amenaza de un vertebrado introducido?.” Fundación Charles Darwin, Santa Cruz-Galápagos
Sulloway, F. (2015). “Opuntia Cactus Pérdida en las Islas Galápagos, 1957-2014,” Puerto Ayora.
Sulloway, F. J., Noonan, K. M., Noonan, D. A., and Olila, K. J. (2013). Documenting Ecological Changes in the Galápagos since Darwin´s visit. 1-32.
Diana Valeria Flores Tabango, a BsC graduate in Biological Sciences, is a research assistant for the Charles Darwin Foundation botanical collection and herbarium. She is based at the Charles Darwin Research Station on Santa Cruz Island, Galapagos.
In 2011 Diana started as a volunteer at the CDF working on the field of marine biology, and in 2013 she became part of the staff as a Research Assistant for the CDF herbarium.
She graduated as a Biologist at the University Central of Ecuador in Galapagos. She investigated the germination rate and viability tests of the endemic cactus species from Plaza Sur (Opuntia echios var. echios), as part of the Charles Darwin Foundation´s project Galapagos Verde 2050 under the component of ecological restoration.
For more information about the work of CDF please visit: www.darwinfoundation.org