When humans arrive on an island they have an immediate and dramatic impact on the ecosystem, according to a new international study which included scientists from The Australian National University (ANU).
The study looked at 27 remote islands across the globe and found they had something in common.
"When humans arrive on these islands the ecosystem immediately starts to change. But even more importantly, it keeps changing - it's still changing now in most cases," ANU co-author Dr Simon Connor said.
"The change is also permanent. There's no going back because our impact as humans is so profound. This is worrying because the islands have really special biodiversity, including species that aren't found anywhere else in the world."
According to the study's authors, this is the first time this human impact has been documented globally.
The research team used pollen records dating back 5,000 years, which offer a clear picture of the vegetation that grew in the landscape.
"On some islands we see the complete loss of classic lowland tropical rainforest ecosystems, and they're replaced with more savannah type landscapes," co-author Associate Professor Janelle Stevenson said.
"The transformation doesn't always mean loss of biodiversity - the diversity can change to something that wasn't there to begin with. With sea travel becoming more common you also get a lot more introduced species."
The researchers say these islands are like tiny microcosms that represent what happens around the globe generally when humans arrive.
"This study shows humans are capable of really dramatically altering an ecosystem in irreversible ways. We have to be really careful about how we manage our own environment here in Australia," ANU co-author Professor Simon Haberle said.
The research has been published in Science. The study was led by Dr Sandra Nogué from the University of Southampton.