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Ibiza and Australia dispute the largest and oldest living plant on the planet

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At the bottom of the strait that separates the islands of Ibiza and Formentera grows plant more extensive and long-lived of the planet: an immense meadow of Posidonia oceanica (an underwater seagrass) that actually forms a single specimen with a minimum estimated age of 100,000 years and an extension and length of around eight kilometers. In fact, it is the “largest living organism that has been documented so far” worldwide, according to an international team of scientists in 2006, made up of experts from the CSIC, the University of the Balearic Islands and others from Portugal, the Caribbean and the United States.

However, during the last days another study has just proclaimed it as “the largest and oldest plant in the world” another different species, located in Australiabut which curiously shares many similarities with the Posidonia oceanica from Ibiza and Formentera. What’s more: it is actually also a plant of the same genus, called Posidonia australis.

Researchers from the University of Western Australia (UWA) have discovered a meadow of this marine plant in Shark Bay, in the west of the country, which according to their calculations would be 4,500 years old and would extend over 180 square kilometers, with a length of about 10 kilometers, As published in the scientific journal Proceedings of the Royal Society.

Scientists were studying the genetic diversity of the Shark Bay seagrass meadows when they realized that these seagrass beds were actually made up of a single plant, or a ‘clone’ from the same seed, which would have replicated successively.

The lead author of the study, Jane Edgeloe, from the UWA, explained in a statement that her team generated a ‘fingerprint’ using 18,000 genetic markers to check the diversity of this grassland: “The answer left us speechless: there was only one plant, which has spread over 180 square kilometers in Shark Bay, which makes it the largest known plant on Earth,” he added.

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To calculate the age of the specimen, the scientists counted the estimated total area of ​​the prairie in the area and divided it by the range of annual extension of the rhizome (from 15 to 35 centimeters per year). Thus, a minimum age of 4,500 years was obtained.

But, despite the announcement made by the Australian team, the oldest via plant in the world is still the one that lies under the seabed of the Pitiusas Islands. Between Ibiza and Formentera there is a gigantic specimen of similar proportions to the one in Australia, but much longer. Its 100,000 years far exceed the 4,500 of Posidonia australis.

The posidonia of Ibiza and Formentera, “the longest on the planet”

But how is it possible that, being younger the Australian, has expanded to reach the same surface as the Ibizan, in much less time?

Oceanographer and posidonia expert Carlos Duarte offers the answer. Familiar with the research at the University of Western Australia (he himself was the director of its ocean institute in the past decade), Duarte explains that this is because “the Australian angiosperm species grows much faster than the Mediterranean one”.

In any case, the meadow between Ibiza and Formentera “is still the longest-lived plant on the planet,” he clarifies.

“This is not a Guinness Book of Records competition, but the new study confirms that marine angiosperms are the largest living organisms on the planet, in addition to playing a fundamental role as carbon sinks,” says Duarte, who He currently works at the University of Saudi Arabia.

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In the entire Mediterranean there are about 50,000 square kilometers of this plant, endemic to this sea, and of this surface, five percent is found in the Balearic Islands, which means between 2,000 and 3,000 square kilometers of underwater meadows.

However, the Posidonia oceanica could have the days numbered. The annual loss of this species in the Mediterranean exceeds 5%, according to the University of the Balearic Islands, due, among other causes, to the ‘tropicalization’ suffered by this seawhere water temperatures rise even more than air temperatures, which favors the expansion of numerous invasive alien species and weakens the native ones.

In addition, it must be taken into account that Posidonia grows very slowly, at a rate of less than two centimeters a year, and also has a low seed production, which, according to scientists, makes any loss it suffers practically irreversible. , because its recovery takes centuries.

“Champion in sequestering CO2 from the atmosphere”

Professor Carlos Duarte has highlighted the exceptional role played by these underwater meadows in capturing CO2 from the atmosphere, to the point that this scientist qualifies said plant as “champions of carbon sequestration in our biosphere”. “One hectare of Posidonia meadows in the Mediterranean sequesters as much carbon as 15 hectares of Amazonian forest and, in addition, it does not burn”, he affirms in reference to the fires that the aforementioned tropical forest suffers.

The uncontrolled anchoring of yachts that this meadow suffers in summer, which supports a tourist pressure incompatible with its conservation, as well as the polluting discharges from submarine outfalls and ships, in addition to the heating of the water, put this very important species in a very compromised situation.

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Environment section contact: crisisclimatica@prensaiberica.es

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