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The human footprint causes more changes in the vegetation of the islands than the climate

The island of Iceland It was colonized about 1,000 years ago by Vikings, a navigating Nordic people with a strong negotiating character. The raw materials and resources offered by the remote island in the Arctic Ocean aroused strong interest from newcomers, who forever turned the economy of the area, northern Europe and most of the world upside down. But the Vikings left a mark on the natural environment that would never be erased again, like many other peoples who have colonized islands around the world.

In Iceland, although the vegetation shows changes in the climate prior to human arrival, from the year 920 the activity of the first settlers accelerated changes in the vegetation, intensified the erosion and destroyed forests in favor of pastures. The wood needed to build boats, stone and metal from such a resource-rich island were looted for years.

The changes caused by human action on the islands are irreversible and are constantly reproduced, centuries after colonization.

Today, most inhabited islands around the world have experienced at least two waves of settlements different, each with characteristic changes and increasingly complex legacies. This is due to the irreversible condition of the changes that have occurred, which are increasingly rapid.

The article, published in the journal Science, indicates that the alterations in the plant life of the ecosystem of an island produced by human colonization are 11 times greater than those due to the climate or effects such as previous volcanic eruptions. The research has been carried out on 27 islands around the world.

This modification caused by human action is irreversible and is constantly reproduced, centuries after colonization. The first author of the article is the researcher Sandra Nogué, from the University of Southampton (United Kingdom) analyzed the data and shaped the work while she was a visiting researcher at the Center for Ecological Research and Forestry Applications (CREAF, for its acronym in Catalan), a period in which she collaborated with the researcher Josep Peñuelas.

The islands, an ideal laboratory

The study makes it possible to quantify the human impact on a landscape. Until now it was difficult to separate the effects of climate and other environmental impacts from those caused by early humans on the continental masses.

The team has studied fossilized pollen 5,000 years ago, extracted from sediments from the 27 islands, which has allowed us to understand the composition of the vegetation of each one and how it changed from the oldest pollen samples to the most recent ones.

The islands are ideal laboratories to measure human impact, since most were colonized in the last 3,000 years, when climates were similar to today

Sandra Nogué, principal investigator of the work

“The islands are ideal laboratories to measure human impact,” says Sandra Nogué, “since most were colonized for the last 3,000 years, when the climates were similar to the current ones. Knowing when an isolated territory was colonized makes it easier to scientifically study the changes in the composition of its ecosystem in previous and subsequent years, and provides a dimension of its magnitude ”.

That is why it has been key to know that the population of the islands of the Polynesia it arrived 3,000 years ago to remote areas such as Poor Knight (New Zealand, South Pacific Ocean) and also to Fiji (South Pacific); It is 2,800 years ago that they arrived in New Caledonia (Pacific), and 370 years ago that Europeans landed in Cape Verde (North Atlantic), considered the first tropical European colony in the Atlantic. To some islands of the archipelago of the Canary Islands (Atlantic) the European population arrived between 1,800 and 2,000 years ago, while in the Mauritius Islands (Indian Ocean) only 302 years ago that European colonizers set foot.

“The environment of those that were colonized by more modern populations, such as the Galapagos (Ecuador, Pacific Ocean, inhabited for the first time in the 16th century) or the New Zealand Poor Knight, received more impact,” explains Nogué. “On the other hand, those previously occupied received more primitive populations, who developed a life more linked to the natural rhythm and more sustainable and, therefore, the territory was more resilient to colonization.”

As an example, the study shows that islands reached by humans more than 1,500 years ago, such as Fiji and New Caledonia, experienced a slower rate of change.

Although ecosystems are not expected to recover their original situation, the work can help guide restoration efforts and understand the capacity of the territory to respond to change.

“This difference in change could mean that the previously populated islands were more resistant upon the arrival of humans. But it is more likely that the land use practices, technology and species introduced by the later settlers were more transformative than those of the former, ”explains the lead researcher.

Although ecosystems cannot be expected to recover their pre-settlement situation, the work can help “guide restoration efforts and understand the territory’s responsiveness to change,” says Josep Peñuelas.

From Fiji to Cape Verde

The trends they were observed in geographic locations and climates as diverse as those of the South Pacific Ocean, the Indian Ocean, the South Atlantic or the Arctic, among others. Changes in ecosystems can also be due to various natural factors, such as earthquakes, volcanic eruptions, extreme weather conditions, and changes in sea level.

Anthropogenic impacts on islands are long-lasting components of these systems that often involve initial cleanup and are exacerbated by the introduction of species and the spread of endemics.

However, the research team has found that disturbances caused by humans outweigh all these phenomena and the change is usually irreversible. Therefore, they advise that conservation strategies take into account the long-term impact of humans and the degree to which current ecological changes differ from those of pre-human times.

The results show little evidence that the ecosystems affected by human colonization resemble the dynamics present before their arrival. Thus, anthropogenic impacts on islands are long-lasting components of these systems that often involve initial cleanup (for example, through the use of fire), and are exacerbated by the introduction of a number of species and the extinction of endemics. , in addition to continuous disturbances.

Reference:

Nogué, S. et al. “The human dimension of biodiversity changes on islands”. Science (2021). DOI: 10.1126 / science.abd6706.

Rights: Creative Commons.

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