In their study, Jetz and Buckley confirmed that reduced numbers of predators and competitors accompany high lizard densities on islands across the world. The two biologists concluded that an average acre of mainland contains 52 lizards while an island acre contains 777 lizards. This difference in density persisted when the scientists controlled for location and environmental conditions.

The ecology of islands is particularly important because, while the worlds more than 100,000 islands constitute only 7 percent of the global land surface, they contain many of the earths species with numerous species restricted to single islands, says Buckley. 500 million people depend on island ecosystems for their food and livelihoods.

The study suggests that islands are particularly sensitive to the loss and gain of species. Species introductions have had dramatic consequences for islands. Introduced mongooses have devastated island populations of lizards and introduced snakes have caused the loss of birds and lizards on islands.

Cases of species introductions wreaking havoc on islands are likely to become more common as the islands face increasing pressures from population growth, tourism, development, and climate change, says Jetz. The consequences of island vulnerability have already been observed as island species account for half of known animal extinctions and a full 90 percent of known bird extinctions in the last 400 years. Our study suggests that islands will continue to be vulnerable worldwide.

Many people, myself included, enjoy visiting islands for their spectacular wildlife, adds Buckley. Our research suggests that we must be particularly careful to limit th
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Contact: Kim McDonald
kmcdonald@ucsd.edu
858-534-7572
University of California - San Diego
1-May-2007