Gonzalo Rivas-Torres1,2,3,4, Lorena Benitez1, Christian Sevilla5, Danny Rueda5 and Carlos Mena1,3
1Colegio de Ciencias Biológicas y Ambientales and Galapagos Academic Institute for the Arts and Sciences, Universidad San Francisco de Quito, Diego de Robles S/N e Interoceánica, Quito, Ecuador
2Department of Wildlife Ecology and Conservation, University of Florida, 110 Newins-Ziegler Hall, Gainesville, FL 32611, USA
3Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
4Galapagos National Park scientific collaborator
5Galapagos National Park Directorate, Santa Cruz, Ecuador
Here we present the results of a mixed, systematic and low-cost methodology to define and map native vegetation and the distribution of pervasive invasive plants that generally affect island resident ecosystems. After obtaining preliminary legends defined by experts: i. Landsat 8/OLI images were used to perform an object classification analysis; ii. high resolution images obtained by drones (UAVs) were taken for mapping validation; and iii. verification was performed in the field and in workshops to obtain the vegetation map of the iconic Galapagos National Park (GNP). This project (which includes species mapping using drones), revealed that 53.6% of the GNP is covered by nine native ecosystems and ~2.2% of this protected land is canopy dominated by invasive species. The so-called “dry” native ecosystems cover 40.8% of the GNP and only 12.8% of this protected area is covered by “wet” and “transitional” native ecosystems. Among the latter, those distributed in the highlands, covered only 4.8% of the protected area and are very threatened by the invasive species mapped here, which predominate in these sites. In addition, three native ecosystems occurring in the GNP were spatially described for the first time including the “Highland deciduous tallgrass”, which despite being mainly in the upper parts of the Isabela volcanoes, present a type of vegetation similar to dry coastal forests (due to climatic inversion).
Cedrela odorata, Pennisetum purpureum, and Psidium guajava were the main invasive plants dominating the GNP canopy. The highly noxious Rubus niveus was the only invasive species dominating areas among the five (out of 18) infested islands.
The methodology detailed here proved useful to provide accurate spatially explicit island vegetation data, has a potential for replication in time, and is expected to aid the suitable management of highly endangered and unique biotas in this and other tropical island biomes.