Research has shed new light on the impact of humans on Earth’s biodiversity. The results suggest that the rate of change in plant life in an ecosystem increases dramatically in the years following human settlement, with the most dramatic changes occurring in settled places over the past 1,500 years.
An international research team has studied fossilized pollen dating back 5,000 years, extracted from sediments on 27 islands. By analyzing the fossils, they were able to gain an understanding of the make-up of each island’s vegetation and how it went from the oldest to the newest pollen samples.
The study was led by Dr Sandra Nogué, Senior Lecturer in Paleoenvironmental Sciences at the University of Southampton, UK and Professor Manuel Steinbauer of the University of Bayreuth, Germany and the University of Bergen, in Norway. Doctoral student Dr Alvaro Castilla-Beltrán was also a member of the Southampton team.
Dr Nogué said: “The islands provide the ideal environment to measure human impact, as most have been colonized in the past 3,000 years, when climates were similar to current conditions. Know when the settlers arrived on an island means scientists can study the makeup of its ecosystem. changed in the years before and after. “
The results, published in Science, showed a consistent pattern on 24 of the islands where human arrival accelerated the renewal of vegetation by a factor of eleven on average. The fastest changes have occurred in islands that have been colonized more recently – like the Galapagos, first inhabited in the 16th century. Islands where humans arrived over 1,500 years ago, such as Fiji and New Caledonia, have seen a slower pace of change.
“This difference in change could mean that previously populated islands were more resistant to human arrival, but it is more likely that land use practices, technology, and species introduced by later settlers were more resilient. transformative than those of the early settlers, ”explained Dr Nogué.
The trends have been observed in a range of geographic locations and climates, with islands like Iceland producing similar results to Tenerife and other tropical and temperate islands.
Ecosystem change can also be driven by a number of natural factors such as earthquakes, volcanic eruptions, extreme weather conditions, and sea level changes, but the researchers found that the disturbances caused by humans overcome all of these events and that change is often irreversible. They therefore advise that conservation strategies must take into account the long-term impact of humans and the extent to which ecological changes today differ from prehuman times.
“While it is unrealistic to expect ecosystems to return to their pre-colonization conditions, our findings can help inform targeted restoration efforts and provide a better understanding of islands’ responsiveness to change. », Concludes Dr Nogué.
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