Species at Risk: Islands Under Pressure
Living on an Island Can Be Risky Business
Perhaps at one time or another you’ve dreamed of exploring islands such as Madagascar or the Galapagos. If that’s true, you’re not alone. For hundreds of years, naturalists have been fascinated with the unusual wildlife found on islands, especially “endemic” wildlife — wildlife that naturally lives nowhere else in the world.
When it comes to the loss of species, islands can be especially vulnerable for several reasons: Compared to large continental landmasses, islands have limited areas of natural habitat with relatively low animal populations. Often, islands have no large and/or aggressive predators, and therefore native animals have never evolved survival skills to protect themselves from predators. And so, when a human, rat, domestic cat or another predator suddenly shows up on an island, the result can be a natural disaster.
Case Study: Brown Snake Invades Guam
Just after the World War II, the brown tree snake was accidentally brought from its native habitat on several South Pacific Islands including New Guinea to Guam, probably in lumber shipments. The snake, which grows up to eight feet long, arrived without any of its natural predators that would normally keep its numbers under control.
Since that time, the bird-eating brown snake has eliminated the following birds from Guam’s wild habitats:
• nightingale reed-warbler
• Mariana fruit-dove
• Guam flycatcher
• Guam rail
• Micronesian kingfisher
• bridled white-eye
• cardinal honeyeater (Guam subspecies)
• rufous Fantail (Guam subspecies)
• white-throated ground dove (Guam subspecies)
On other vulnerable islands such as Madagascar, humans have eliminated more species — including all of the island’s giant lemurs and elephant birds — than any other animal arriving on its shores. Widespread hunting and cutting forests did the job. But the result was similar: remarkable species vanished for all time.