Sign In
Australia; New Zealand; Pacific; International; ACT
Media release
From:
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.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Matiu Prebble, Research Fellow, School of Earth and Environment, University of Canterbury; and School of Culture History and Languages, College of Asia and the Pacific, The Australian National University
An international research team studied fossilised pollen dating back 5000 years, extracted from lake and swamp sediments on 27 islands. Associate Professor Janet Wilmshurst, Principal Scientist at Manaaki Whenua, and I are two New Zealand-based co-authors who contributed several fossil datasets from the Pacific Islands and Aotearoa to this global study.
Our team's research has found that the rate of change in island biodiversity increases significantly after initial human settlement, with the most dramatic changes occurring on islands settled relatively late. This includes Aotearoa New Zealand and many Pacific Islands.
Islands, especially in our region, provide excellent case studies to measure the ecological impact of people as they are highly sensitive to biodiversity changes. Because we know precisely when people arrived on different islands, we can study how the composition of its ecosystem changed before and after using fossil pollen.
The results, published today in Science, showed a consistent pattern on 24 of the islands where human arrival accelerated the turnover of vegetation by, on average, a factor of eleven. The most rapid changes occurred in islands that were settled most recently that include Aotearoa and French Polynesia. But even greater rates of change are observed on the Galápagos Archipelago, first inhabited in the 16th Century. Islands where humans arrived around 3000 years ago, such as Fiji and New Caledonia, saw a slower rate of change.
It could be interpreted that islands such as Fiji were more resilient to human arrival, but it is more likely that the land-use practices, technology and introduced species brought in during later European colonisation of other islands had a more profound impact than those of the earlier settlers.
These trends were observed globally including in the North Atlantic and Mediterranean islands, with very different climates, and while ecosystem change can also be driven by natural factors such as volcanic eruptions, earthquakes, extreme climate events, and changing sea levels, the researchers found that human activity outweighs all of these factors.
In Aotearoa and French Polynesia, we found that regardless of human arrival histories, vegetation change is still profound, even on some islands that have had little recent human settlement. This fits with what we find globally, that once an island has been occupied, the biodiversity changes are often irreversible.
Our research team advises that current island biodiversity protection strategies must account for the long-term impact of people and the degree to which ecological changes today differ from pre-human times.
Aotearoa is renowned for its biodiversity conservation successes, especially on island reserves, but we have found that legacy of human activity makes any aim of restoring pristine wilderness mostly implausible. Regardless, the cultural interests of mana whenua now rightly take precedence with recognition of substantial cultural heritage on the offshore islands, as well as acknowledgement of enduring living traditions of sustainable biodiversity management. It may be encouraging that it is likely that the rate of biodiversity change will slow, albeit in hundreds of years.
