Principles of Ecology
Extra Credit Blog
April 23, 2011
"Giant Tortoises Show Rewilding Can Work"
ScienceDaily -- April 21, 2011
"'Rewilding with taxon substitutes', the intentional introduction of exotic species to fulfill key functions in ecosystems following the loss of recently extinct species, is highly controversial, partly due to a lack of rigorous scientific studies."
 |
| Photo I: Ile Aux Aigrettes |
 |
| Photo III: The exotic giant Aldabra tortoise (Aldabrachelys gigantea) |
 |
| Photo II: Location of the Island |
 |
| Photo IV: Ebony Diospyros egrettarum (Ebenaceae) |
Diospyros egrettarum (Ebenaceae) is an ebony tree that once covered the island Ile aux Aigrettes, but is now endangered due to excessive logging that took place up until the ‘80s. The decimation of this once-ebony forest was measured in 2007 when researchers surveyed and mapped the entire island, finding 3,518 adult trees. They found that large sections of the island were completely stripped of this tree, namely in the northern and eastern coastal areas nearest the mainland. This is where logging was most intense. Even though the destructive logging ended more than thirty years ago, there had been no regeneration in these bare areas of the island because with the extinction of the island’s native giant tortoises, there were no fruit-eating animals to disperse the endangered tree’s seeds.
In 2000, the exotic giant Aldabra tortoises (Aldabrachelys gigantea) were reintroduced to the island as an attempt to disperse the slow-growing ebony. The tortoises consumed the large fruits and dispersed large numbers of ebony seeds, and “the process of passing through a tortoise's gut also improved seed germination, leading to the widespread, successful establishment of new ebony seedlings in the heavily logged parts of the island.”
Christine Griffiths and her colleagues, of Bristol’s School of Biological Sciences, have presented the first empirical evidence of the success of re-wilding in their paper (published in Current Biology on April 21). They report that, "Our results demonstrate that the introduction of these effective seed dispersers is aiding the recovery of this critically endangered tree whose seeds were previously seed-dispersal limited. Reversible re-wilding experiments such as ours are necessary to investigate whether extinct interactions can be restored." Professor Stephen Harris, co-author of the study, said, "Ecological restoration projects generally involve the plant community, as more often the animal components are extinct. There is, however, increasing evidence that restoration ecologists should be most concerned with the decline of species interactions, rather than species extinctions per se. Species interactions structure ecological communities, and provide essential ecosystem processes and functions such as pollination, seed dispersal and browsing, that are necessary for the self-regulation and persistence of a community."
This is an important ecological topic of discussion because this case demonstrates the success of re-wilding experiments. Not only were the researchers able to reestablish the population of this endangered tree, but by bringing in the tortoises they were also able to reestablish the interaction between the two species. Not only do interspecies interactions such as this relate to our Principles of Ecology class, but they are also a fundamental aspect of much of our world, as most species are connected, and influence, one another in some way.
Citations
News article found at: http://www.sciencedaily.com/releases/2011/04/110421122331.htm
No comments:
Post a Comment