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The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity
Ecology Letters, Volume: 17, Issue: 2, Pages: 144 - 154
Swansea University Author: Cynthia Froyd
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The giant tortoises of the Galápagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but...
|Published in:||Ecology Letters|
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The giant tortoises of the Galápagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelago's only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500–700 years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subsequently leading to the decline of several now-rare or extinct plant species.
These results identify that, far from being the pristine ecosystems of common perception, the Galapagos Islands, despite their uniquely high rates of native species retention, have experienced significant habitat transformations since human arrival in the archipelago. The Galapagos upland Sphagnum crater bogs were found to be a relatively recent development rather than historic ecosystem components, replacing former (and now exceptionally rare) open water wetland habitats, likely as a consequence of the loss of tortoises from the highlands. This has important conservation implications both for the species and more widely, in terms of ecosystem restoration and conservation. These findings support growing evidence of the extent of the ecological consequences of the extinction of large herbivores globally and identify an aspect that is often not considered the effect of megafaunal loss on specialised wetland habitats and the unique organisms and ecosystem functions they maintained
Coprophilous fungi; ecosystem engineer; Galápagos Islands; giant tortoise; megafaunal extinction; wetlands
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