An Ecosystem Balancing Lesson

January 23, 2009


The island of Macquarie, which is south of Australia and administered by the Australian state of Tasmania, is facing major “environmental devastation” caused by the removal of feral cats from the island. The island is a UNESCO Biosphere Reserve, a World Heritage Reserve, and a Tasmanian State Nature Reserve. It has all these classifications to give it the maximum protection possible. Regardless, species that are not native to the island are killing the native plants and animals.

Cats were killing tens of thousands of native seabirds, some of which are classified as threatened.  In a project to stop the birds from becoming extinct, cats were eradicated from the island after several decades of attempts. Now the rabbit and rodent non-native populations, which were being kept in check by the cats, have exploded. Rabbits are destroying the vegetation and the rats and mice are eating the seedlings, bird’s eggs and fledglings.

This is what happens when you meddle with the ecosystem, even with the best of intentions, without thinking long and hard, says the article. “The lessons for conservation agencies globally is that interventions should be comprehensive, and include risk assessments to explicitly consider and plan for indirect effects, or face substantial subsequent costs.”

Rabbits, rats and mice will start to get eradicated in 2010 to help the island and it’s native plant and bird species recover from the invasion that has lasted about a century. For more details go the the January 13, 2009 article by Michael Casey and the Sydney Morning Herald April 12, 2007 article.

This can be used when teaching the balance of an ecosystem in Intermediate Science and Living Environment Core Curriculums.

Other cases of ecosystems affected by nonnative species are in New Zealand, Hawaii, Pacific Islands, Aleutian Islands, etc.

Which cases do you know about?