Impact of human settlements on island ecosystems — ScienceDaily

The research has shed new light on the impact of humans on the biodiversity of the islands. The results show how human colonization has altered the forest across the islands of Macaronesia, including the loss of landscape authenticity.

Ocean island ecosystems are unique and often contain species restricted to specific islands or groups of islands. They are also vulnerable to disturbances.

To provide a timeline of how humans have altered these territories over the centuries, a team led by the University of Southampton studied several indicators of landscape change buried in sediments deposited over time periods of up to ten thousand. year. The team examined samples including fossilized pollen, fungal spores decomposing feces that indicate the presence of large herbivores, charcoal fragments indicating the use of fires as well as the composition of the sediment -same.

Their findings, published in the journal PNAS, showed that while island forests have changed naturally over thousands of years, the arrival of man to the Canary Islands around 2000 years ago and Cape Green 500 years ago led to increased fires and rates of soil erosion, the latter associated with the introduction of non-native livestock such as goats and pigs. A particular type of forest typical of Macaronesia, called thermophilic forest, and characterized by emblematic species such as the dragon tree, was the most impacted. In Cabo Verde, data suggest that island vegetation is undergoing a process of homogenization due to human pressures and that the uniqueness of individual island ecosystems is being lost.

The team also found that the early use of Canarian forests by indigenous settlers appeared to have limited impact on native vegetation, such as the laurel forest on the island of La Gomera. This may be due to smaller populations, which generally interact and trade with other nearby islands. In contrast, colonial-era settlers who arrived in the 15th century adopted far more aggressive acts of deforestation, land-use change, and the introduction of non-native species due to much broader trade networks that had a much greater effect.

Dr Sandra Nogué Bosch, senior lecturer in paleoenvironmental science at the University of Southampton, said: “The contrast in the long-term history of different ecosystems, such as island forests, helps put into perspective the strength of transformation that humanity is releasing all over the world.

Professor Mary Edwards, Professor of Physical Geography at the University of Southampton, said: “We hope that local and international institutions tackling environmental challenges in the region can use the new knowledge about the composition and variability of the past. ecosystems to restore natural parks and other parts of island landscapes. “

Dr Alvaro Castilla-Beltrán, who completed his PhD at the University of Southampton, explained: “This evidence from past environments provides valuable evidence about how forests have responded to human actions and how best to restore these landscapes, which have in some cases suffered serious damage, transformations and loss of species.

The team plans to continue using state-of-the-art methodologies to be able to answer these questions, unlocking the potential of geochemical tools and searching for ancient DNA preserved in sediments.

After analyzing the consequences of human impacts on the Canary Islands and Cape Verde, the team plans to continue its studies on other archipelagos to deepen the evolution of island habitats.

“Other important research questions remain open, for example, what was the role of climate change in these processes in the past, and how will global warming affect future ecosystems? What has been the local impact of extreme natural phenomena such as volcanic eruptions – such as the one currently active in La Palma – and how has island life changed the cultures of those peoples who settled them?We will also continue work on other archipelagos to offer a new perspective of the human footprint in these fascinating territories”, concluded Dr. Nogué Bosch.