http://evol-eco.blogspot.com/
However you skin them, cats
have important ecosystem consequences
Islands experience
the greatest impacts from the invasion of non-indigenous species
and are also at the forefront of efforts to eradicate problematic
species and mitigate negative impacts. Bergstrom et al. elegantly
studied the habitat and ecosystem consequences from the eradication
of feral cats from Macquarie Island, a subantarctic island and a
world heritage site administered by the state of Tasmania,
Australia. This island has undergone a series of invasions and both
cats and rabbits were introduced in the 19th century. Cat predation
resulted in drastic declines in seabird populations, likely causing
two extinctions, and thus a cat eradication programme began in 1985
with the last cat killed in 2000. The authors recognized that the
feral cats had become fully ingrained in the island food web, and
they show that despite the introduction of the Myxoma virus prior
to the cat eradication, rabbit populations exploded after the cat
removal. These large rabbit populations caused pervasive vegetation
changes. The authors sampled plots before and after the eradication
and found that vegetation in these plots shifted from large,
long-lived plants to smaller, faster growing species, some of which
are themselves non-indigenous to the island. Further, satellite
imagery revealed that more than one-third of island has since
undergone vegetation change, likely resulting in large-scale
habitat alterations.
What these results
show us is that the consequences of species eradication may be
complex with unintended results. Non-indigenous predators and
meso-predators can become important components of island food webs
–so important that their subsequent removal can have repercussions
felt throughout the entire food web. While trying to protect
seabird populations is undoubtedly worthy of management action
(including eradication programmes), adequately predicting
ecosystem-level consequences should be the basis directing such
activities. Planning for such management activities must include
information gained through experimentation, modeling and natural
history. By using all available tools and knowledge, management
activities can have a better chance of succeeding and harmful
unintended consequences minimized.
Dana M. Bergstrom, Arko Lucieer, Kate Kiefer, Jane Wasley, Lee
Belbin, Tore K. Pedersen, Steven L. Chown (2009). Indirect effects
of invasive species removal devastate World Heritage Island
Journal of Applied Ecology,
46 (1), 73-81 DOI: 10.1111/j.1365-2664.2008.01601.x
Posted by Marc
Cadotte