Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 51

now critically endangered and survives only on small islands that are free of rats and other
predators (Wood et al. 2012). The ranges of the two species no longer overlap (See Figure 3.7)
and the lesser short-tailed bat ( Mystacina tuberculata ) is the only known remaining native
pollinator of D. taylorii . The findings suggest opportunities for translocating D. taylorii to the
kakapo's remaining island strongholds and other islands with endemic nectar-feeding birds
(Wood et al. 2012). This work shows how lost functional links can be revived by combining
palaeoecological work with current ecological studies.
Another example of functional rewilding is taking place on Ile aux Aigrettes, a 25-hectare
island near Mauritius, in the Indian Ocean. Here, critically endangered ebony forests that
have been over-harvested for firewood and timber were not recovering, despite a ban on log-
ging since the 1980s (Hansen et al. 2010). Restoration work began in 1986, but a survey of the
island in 2007 showed that large areas were still denuded, and further studies showed that
only 7 out of over 7,400 ebony fruits of the endemic ebony ( Diospyros egrettarum ) were found
beyond the canopy of maternal trees, so the forests were not expanding. The reason for the
poor dispersal is that since humans arrived in the late sixteenth century, all of the large, fruit-
eating animals such as giant tortoises and giant skinks have been driven to extinction. The
remaining fruit-eating animals and birds are too small to disperse the ebony fruits, and there-
fore a substitute species was needed for the natural dispersal agents that had perished at the
hands of humans. An exotic giant tortoise from Aldabra ( Aldabrachelys gigantea ) was chosen
because it was closely related to the extinct Mauritian tortoises, and was similar ecologically,
having a broad diet that included large fruits. Since the first introductions, tortoise numbers
have increased and dense patches of ebony seedlings have established beyond the canopy of
the ebony forest (Hansen et al. 2010).
Not all introduced species are benign, however, and alien species remain a major concern
in many island ecosystems. Palaeoecology can help to avoid unnecessary eradication efforts
by establishing the true status of 'doubtful natives. In the Galapagos Islands, for example, fos-
sil pollen data showed that six species that had been presumed to be alien were in fact pres-
ent thousands of years before human arrival. Concern over the spread of Hibiscus diversifolius
was alleviated when fossil pollen records showed that it may be re-establishing in areas of
former habitat (van Leeuwen et al. 2008). Similarly, palaeoecological work in the Azores and
Tenerife have established the native status of some plant species that were previously thought
to have been introduced aliens (van Leeuwen et al. 2005, De Nascimento et al. 2009).
Summary: towards wildness?
The extinction of megafauna has had massive impacts on ecosystem structure and function,
but these effects are largely cryptic and poorly understood. By studying African ecosystems,
which retain almost a full complement of megafauna, by understanding functional mis-
matches in today's ecosystems, and by looking for clues in the palaeoecological record, we
can start to understand how ecosystems may have worked if megaherbivores had survived.
This can provide an ecological basis for re-wilding projects, though there are also aesthetic,
cultural, and ethical issues to be considered.