canary islands eemian climate sea level fuerteventura

Canary Islands’ past climate warns of future sea level rise

Ancient climate warning from the Canary Islands

Around 120,000 years ago, the planet was gripped by a slow but turbulent climate shift, and the Canary Islands were not spared. This period, known as the Eemian interglacial, saw temperatures across the archipelago rise between two and four degrees above pre-industrial levels — the same temperature increase predicted for the worst-case climate scenario by 2100. The result was a dramatic transformation of the entire ecosystem, including a significant rise in sea level of up to eight metres in some areas, and the presence of Senegalese marine life now confined to Cape Verde and the Gulf of Guinea.

Fossil footprints of a warmer world

The Eemian period has left fossil traces in several enclaves across the archipelago, offering a glimpse of a time when the islands’ coastlines looked nothing like they do today. One such site is Matorral Beach in Fuerteventura, where a fossil deposit of giant Tethystrombus coronatus snails has been found. These snails are now common in Cape Verde but have completely vanished from the Canary Islands. “During that period, they coexisted with other species in the archipelago,” explains biologist José Luis Martín Esquivel, director of Teide National Park.

The Neanderthal era and rising seas

The Eemian was an exceptionally warm period across the entire planet and coincided with the Neanderthal occupation of Europe. Meanwhile, the fossil record on the Canary Islands’ coasts reveals that “the sea fluctuated considerably, rising by between five and six metres, and in some places up to eight metres,” says Martín Esquivel. He is co-author of a new study, published in the journal Frontiers of Biogeography, alongside José María Fernández Palacios and Enrique Fernández Palacios, which warns that current climate change could produce similar consequences, albeit over a very long timescale — more than 100 years.

Sea level projections for 2100 and beyond

“With a two-degree temperature rise, it has so far been estimated that the sea could rise by up to one metre in the Canary Islands,” explains Martín Esquivel. However, if the warming trend continues over several centuries — as it did during the Eemian — sea levels could reach far higher limits, affecting beaches, infrastructure, and the vulnerability of coastal communities.

The slow, relentless melting of the poles

One of the main causes of such a dramatic sea level rise was the melting of the polar ice caps. “When temperatures reached two degrees above normal, it took 1,000 years for the sea level to rise,” the researcher notes. This means that, in today’s scenario, even if global temperatures returned to normal tomorrow, “the glaciers would continue to melt for another 100 years.” Sea levels will therefore keep rising because “there is a synergy that operates slowly.” For this reason, although a sea level rise of one or two metres is forecast for 2100, it is highly likely that the sea will swallow a much larger part of the Canary Islands due to this delayed effect.

Natural vs. human-driven warming

Unlike current climate change, which is driven by human activity — specifically CO2 emissions from industry and transport — the ancient temperature rise had a natural origin. “It was not related to carbon dioxide, which remained at around 300 parts per million (ppm); the temperature rose due to other factors, such as solar cycles or even a possible increase in volcanic activity,” explains the researcher. Despite this difference, and the fact that the warming was much slower than today’s, “the end result would be the same.”

A glimpse of a different archipelago

On a planetary scale, one consequence was that large forests extended much further north than they do today. In the Canary Islands, this brought species now adapted to warmer climates and created a very different picture of the archipelago. Faced with the evidence of the past, researchers argue that the Canary Islands are undergoing an “eemification” of nature.

Already happening: the signs are here

The lowering of the cloud sea, an increase in wildfires, the altitudinal shift of plant species, the tropicalisation of waters, and the arrival of tropical marine and terrestrial species to the islands are all phenomena that completely transformed the Canary Islands during the Eemian and, over recent decades, have begun to appear progressively once again. “We have more DANA weather events than 20 years ago, calima dust intrusions are far more frequent, and ciguatera fish poisoning is now a real issue — to the point that health authorities have specific protocols for dealing with it,” the researcher stresses.

Moreover, data gathered in recent years shows that temperatures have already risen by one and a half degrees — almost three degrees in the case of Tenerife’s summit, the worst affected area. Heatwaves are becoming more intense, sea temperatures have risen by nearly half a degree, and the Canary Islands have already lost ten centimetres of land in the last 30 years.

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