Regeneration of vegetation on Santa Fé and Pinta islands, Galápagos, after the eradication of goats

Published source details Hamann O. (1979) Regeneration of vegetation on Santa Fé and Pinta islands, Galápagos, after the eradication of goats. Biological Conservation, 15, 215-235.
Share Tweet Email

Summary

Introduced goats Capra hircus have had a devastating impact on the flora of some oceanic islands. In the 1950s goats were introduced to Pinta (59 km²; altitude 650 m) in the Galápagos (Ecuador) where their numbers rapidly grew. Grazing and browsing opened up the forest and shrubland with some endemic plants severely affected and close to extinction. The Galápagos National Park Service (GNPS) initiated a goat eradication campaign and around 40,000 goats were removed during 1971–1977; at the time of this present study it was estimated that a few thousand were left. On Santa Fé (24 km²; altitude 259 m), goats had also been introduced (sometime prior to 1905) but were eradicated in 1971. The responses of vegetation to goat reduction or removal on these islands were monitored in permanent plots.

Pinta: Four permanent quadrats were established in 1970 and two more in 1973. Five of these (two 10 x 10 m quadrats in lowland dry season deciduous woodland/savanna; three 5 x 5 m quadrats in upland (400 m or more) evergreen scrub/woodland habitats) were included in this study.Since 1970, five examinations vegetation in these quadrats were made.

Santa Fé: In 1972 and 1973, six permanent 10 x 10 m quadrats (mostly in dry season deciduous woodland/savanna habitat but some with an evergreen component) were established and surveyed. Four subsequent examinations of vegetation in these were made up to 1977.

Analysis of vegetation in the permanent plots showed that eradication or reduction of the populations of goats was followed by vegetation regeneration.

Santa Fé: Since eradication of goats in 1971, the density of woody plants in the quadrats increased. However, only about half the woody species present were recolonising and increasing inabundance. Some species appeared to have been reduced to such small population size that natural re-establishment is likely to be very slow or may not occur at all; recolonisation is perhaps exacerbated by the aridity of the climate.

Pinta: In the lowlands (were goats absent) rapid regeneration to the original dry season deciduous vegetation was apparent, with density and number of woody plant species occurring in the quadrats increasing over time. Almost all species of woody plants appear to have survived in sufficient numbers to enable recolonisation. Rapid regeneration of evergreen vegetation in the humid uplands was also recorded as grazing pressure diminished, with density and number of woody plant species increasing, and herb cover reverting into more fern-rich communities. However, it is as yet unclear whether regeneration will lead to re-establishment of the evergreen vegetation originally present.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.science-direct.com