Isabela is the largest island in the Galapagos. Being an inhabited island, it is invaded by plants introduced near human settlements, especially the agricultural area. The effort to control invasive plants is recent.

WORST INVASIVE PLANTS IN GALAPAGOS* Blackberry (Rubus, 5 varieties) Guava (Psidium guajava) Cascarilla o Quinina (Cinchona pubescens) Cedrela (Cedrela odorata) Supirosa (Lantana camara) Sauco (Cestrum auriculatum) Maracuyá (Passiflo) Pomarosa (Syzygium jambos) Hoja del aire (Bryophyllum pinnatum) Pasto elefante (Pennisetum purpureum) Laurel (Cordia alliodora) Cabuya (Furcraea hexapetala) Sauco macho (Citharexylum gentryi-Verbenaceae) Tulipán africano (Sphatodea campanulata) Zaragoza (Aristolochia odoratisima) Higuerilla (Ricinus communis) Poleo (Hyptis pectinata) Saboya (Panicum maximum) Floripondio (Datura y Brugmansia spp) * Marked in bold, invasive plants of Isabela

It is presumed that the introduction of exotic species, mainly plants, began with the arrival of humans in the Galapagos in the seventeenth century, but the greatest introduction occurred in the early nineteenth century, with human colonization of the Islands.

Introduced plants are one of the greatest dangers to the flora of the Galapagos, as many of them are highly invasive, competing with native and endemic plants for light, water, and nutrition.

It is estimated that there are about 700 introduced plants, 50 of which are highly invasive.

Isabela

Isabela, being a young island, does not necessarily have the vegetation zones that other islands have. The relatively recently formed lava surfaces have not developed sufficient nutrients to maintain the variety of vegetation zones found on the other islands.

	NATIVE AND ENDEMIC FLORA OF THE GALAPAGOS » View presentation:

The high part comprises the humid zone and it is divided into several sub-zones. The Scalesia spp. area consists of Scalesia microcephala on the Alcedo and Darwin Volcanoes, and by Scalesia cordifolia in the Ecuador and Wolf Volcanoes.

The Sierra Negra Volcano, the largest and one of the most active in the Islands, has its northern face usually covered with clouds and mist, which encourages the growth of vegetation.

On Isabela it is estimated that 27% of the flora is introduced.

Guava (Psidium guajava) is the most invasive species, introduced in 1910, which covers 27,000 hectares in southern Isabela. Guava, which is characterized by a high rate of germination and regeneration, spreads rapidly on the fertile plains and areas of Scalesia spp. This weed is slowly covering the plains of the Sierra Negra and Cerro Azul Volcanoes.

The small areas of plains and Scalesia spp. that are left are areas of high value for conservation, because here there are dozens of endemic plant species such as Darwinnothamus spp., communities of native ferns and fern trees (Cythea weatherbyana), Lippia salicifolia, and the varieties of "cafetillo" (Psichotria rufipes and Psichotria angustata).

Lantana camara ("supirosa"), invades the areas of vegetation endemic to the Sierra Negra Volcano, habitat of the Scalesia cordata.

Other invasive plants such as "higuerilla" (Ricinus communis) and "cabuya" or fique plant (Furcraea hexapetala) are found on the San Pedro Hill near the southern coast of Isabela, as well as in the agricultural area north of Puerto Villamil.

In contrast to the other inhabited islands, the common blackberry, introduced in 1989, is not so widespread. There are 'patches' of blackberries which now cover about 20 hectares. However, the seeds are dispersed by birds very quickly, therefore the affected areas that started in the agricultural zone have already reached the protected areas away from populated centers, as well as the slopes of Cerro Azul.

Cedrela covers approximately 6 hectares. At this time there are no specific controls for this plant, but permits are issued to the community to cut trees.

Control, eradication and reforestation on Isabela

In northern Isabela, the Isabela Project for the eradication of goats and donkeys enabled the protection of several endangered endemic plants such as Tournefortia rufosericea and Zanthoxylum fagara. These two species are related to the survival of the tortoises, providing them with shade and capturing moisture.

	CONTROL OF INVASIVE PLANTS » View presentation

In the south of the island, the control of invasive species is the responsibility of the Technical Office of the Directorate of the Galapagos National Park in Puerto Villamil. Field trips for the control of introduced plants are organized from there.

Blackberries are controlled in different places: "Caleta Iguana", the slopes of the Cerro Azul Volcano on the southwest coast of Isabela, "Los Pegas", "Alemania" (slopes of the Sierra Negra Volcano), "Buenaño", "Caleta Iguana", "El Porvenir", "La Llanta", "Cerro Colorado", "El Solitario", "El Porteño" and in the agricultural area (with support from Araucaria XXI).

Guava is currently controlled in the area of "El Cura" and "supirosa" is controlled in "El Infiernillo" and "El Aviador". "Higuerilla" is controlled in San Pedro (a hill in the south of Isabela near the coast), "Alemania", and in the agricultural area.

"Cabuya" is controlled in "El Mango", "San Vicente", "El Porvenir", and "La Llanta".

There is also a reforestation program with a nursery located in the high lands. Native and endemic plants are planted there such as the button mangrove, "rodilla de caballo", black mangrove, manzanillo, sesuvium, Nolana spp., Darwinothamus spp., "uva de playa", "algarrobo", white mangrove, and "algodoncillo".

About 10,000 native and endemic plants have been planted.

These plants are used to reforest mined areas and have been given to the community to be planted in gardens.

This program has counted on the support of:

The Charles Darwin Foundation for the Galapagos Islands (CDF) is an international nonprofit research organization dedicated to providing scientific research, technical assistance and information in order to ensure the success of conservation in Galapagos

Araucaria XXI is the Program for the environmental sustainability of human development in Latin America of the Spanish Agency for International Cooperation Development (SAICD).