Changing nature
Within the Seychelles, changes affecting abiotic conditions and biotic systems define the changing nature of the Seychelles environment. The primary changes in these abiotic conditions are caused by climate change and rising sea levels, and the changes in biotic systems may be seen as a result of tortoise rewilding efforts.
As the climate warms, species that thrive within the range of certain temperatures must move to colder areas in order to stay within their temperature limits. In order to do so, most species must migrate either towards the polar-regions or upslope towards higher elevations (Loarie et al, 2009, 1052). Due to the island nature of the Seychelles, however, species are not able to move pole-ward, and so species are forced to move upslope to ensure that they stay within the temperature ranges that they are best adapted for. This migration can result in intense interspecific competition, and the ecosystem may be destabilized. As temperatures at higher elevations moves out of the ideal range for species adapted to and established at higher elevations, species may be threatened, biodiversity may be lost, and novel ecosystems may thrive. It is thought that climate change has already brought about changes in rainfall and temperature and this has led to the extinction of Rhachistia aldabrae, a small tree frog (Gerlach, 2009). Furthermore, the collapse of sea-grass in coastal lagoons and marshes throughout the Seychelles has been attributed to climate change (Gerlach, 2009). Collapse of these lagoons has likely led to the extinction of a newly discovered fish species Asterropteryx sp. (Gerlach, 2009). Furthermore, there is cause for concern as there is an increase in potential for invasive species to establish during times of disturbance (Gerlach, 2009). As a result, it is no surprise that the environment of the Seychelles has been described as vulnerable to the effects of climate change (Payet, 2009, 8). Tortoises may not be directly affected, but their habitats may be adversely impacted, having a long term cascading effect on tortoise populations.
Rewilding has affected the biotic systems on islands throughout the Seychelles, as the reintroduction of tortoises has seemed to be both a driver of ecological change (due to the tortoise’s role as an ecosystem engineer) and as a way to build the resilience to change within an ecosystem. The tortoises have seemed to perform well as an example of “the relocation of taxa to restore declining ecosystem processes” (Lunt et al, 2012, 172), as tortoises have been seen to be effective at ensuring the “dispersal of large seeded plant” seed (Seddon, 2008, pp. 408). The areas that tortoises have affected have seen the regrowth of endemic species that make up the tortoise’s diet. These areas otherwise may have been inundated with invasive species. These changes in ecosystem structure may be substantial enough that ecosystems may experience shifts in the dominant vegetation, which, when combined with the pressures exerted on these ecosystems by climate change, means that there will almost unavoidably be ecological areas created with no precedent.
Rewilding is the act of introducing a species to an area to fill a vacant ecological niche formerly occupied by a species in order to restore the functionality of natural processes. The reintroduction of the giant tortoise to islands throughout the Seychelles is not clearly an act of rewilding, as the specimens that have been reintroduced are not completely foreign to the area, but are a different subspecies than what previously inhabited the area. The line between the act of species reintroduction and the act of rewilding is not clear, but as our case study deals with the reintroduction of a distinct subspecies after centuries of absence, and the introduced subspecies seems to have successfully restored core ecosystem processes (such as native seed dispersal), we feel that our case study may be an example of rewilding.
While the idea of implementing Pleistocene rewilding may still be seen as 'opening Pandora’s Box', the rewilding efforts and programs involving tortoises in the Seychelles seems to have proven that the act of reintroducing low-risk species to act as an ecological replacement can have an overall beneficial effect on an ecosystem. Following the lead of Seychelles rewilding efforts, there have been tortoise rewilding projects proposed to be carried out within other island nations (such as Mauritius) (Griffiths et al, 2010). It remains to be seen just how far beyond the Seychelles tortoise rewilding may be carried out - yet the success of rewilding in the Seychelles certainly provides compelling reasons for expanding rewilding efforts in other compromised ecosystems. In time, these projects may also help develop standard practices and procedures that could be used to facilitate the rewilding programs that focus on non-tortoise species.
As the climate warms, species that thrive within the range of certain temperatures must move to colder areas in order to stay within their temperature limits. In order to do so, most species must migrate either towards the polar-regions or upslope towards higher elevations (Loarie et al, 2009, 1052). Due to the island nature of the Seychelles, however, species are not able to move pole-ward, and so species are forced to move upslope to ensure that they stay within the temperature ranges that they are best adapted for. This migration can result in intense interspecific competition, and the ecosystem may be destabilized. As temperatures at higher elevations moves out of the ideal range for species adapted to and established at higher elevations, species may be threatened, biodiversity may be lost, and novel ecosystems may thrive. It is thought that climate change has already brought about changes in rainfall and temperature and this has led to the extinction of Rhachistia aldabrae, a small tree frog (Gerlach, 2009). Furthermore, the collapse of sea-grass in coastal lagoons and marshes throughout the Seychelles has been attributed to climate change (Gerlach, 2009). Collapse of these lagoons has likely led to the extinction of a newly discovered fish species Asterropteryx sp. (Gerlach, 2009). Furthermore, there is cause for concern as there is an increase in potential for invasive species to establish during times of disturbance (Gerlach, 2009). As a result, it is no surprise that the environment of the Seychelles has been described as vulnerable to the effects of climate change (Payet, 2009, 8). Tortoises may not be directly affected, but their habitats may be adversely impacted, having a long term cascading effect on tortoise populations.
Rewilding has affected the biotic systems on islands throughout the Seychelles, as the reintroduction of tortoises has seemed to be both a driver of ecological change (due to the tortoise’s role as an ecosystem engineer) and as a way to build the resilience to change within an ecosystem. The tortoises have seemed to perform well as an example of “the relocation of taxa to restore declining ecosystem processes” (Lunt et al, 2012, 172), as tortoises have been seen to be effective at ensuring the “dispersal of large seeded plant” seed (Seddon, 2008, pp. 408). The areas that tortoises have affected have seen the regrowth of endemic species that make up the tortoise’s diet. These areas otherwise may have been inundated with invasive species. These changes in ecosystem structure may be substantial enough that ecosystems may experience shifts in the dominant vegetation, which, when combined with the pressures exerted on these ecosystems by climate change, means that there will almost unavoidably be ecological areas created with no precedent.
Rewilding is the act of introducing a species to an area to fill a vacant ecological niche formerly occupied by a species in order to restore the functionality of natural processes. The reintroduction of the giant tortoise to islands throughout the Seychelles is not clearly an act of rewilding, as the specimens that have been reintroduced are not completely foreign to the area, but are a different subspecies than what previously inhabited the area. The line between the act of species reintroduction and the act of rewilding is not clear, but as our case study deals with the reintroduction of a distinct subspecies after centuries of absence, and the introduced subspecies seems to have successfully restored core ecosystem processes (such as native seed dispersal), we feel that our case study may be an example of rewilding.
While the idea of implementing Pleistocene rewilding may still be seen as 'opening Pandora’s Box', the rewilding efforts and programs involving tortoises in the Seychelles seems to have proven that the act of reintroducing low-risk species to act as an ecological replacement can have an overall beneficial effect on an ecosystem. Following the lead of Seychelles rewilding efforts, there have been tortoise rewilding projects proposed to be carried out within other island nations (such as Mauritius) (Griffiths et al, 2010). It remains to be seen just how far beyond the Seychelles tortoise rewilding may be carried out - yet the success of rewilding in the Seychelles certainly provides compelling reasons for expanding rewilding efforts in other compromised ecosystems. In time, these projects may also help develop standard practices and procedures that could be used to facilitate the rewilding programs that focus on non-tortoise species.