Great Barrier Reef’s mangrove islands are expanding despite the advance of the sea

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(ORDO NEWS) — Similar processes are taking place in other Pacific islands (Tuvalu), but it has not previously been noted that they are accompanied by an extremely rapid expansion of coastal mangrove forests.

Scientists from the University of Wollongong (Australia), led by Sarah Hamilton (Sarah Hamylton) explored the islands of the Howick group in the north of the Australian state of Queensland. They are part of the Great Barrier Reef and, like all of its islands, were previously thought to be in danger of near extinction under the rising waters of the oceans.

However, the researchers found the exact opposite process there: the area of ​​the islands is growing, and the mangrove forests that occupy them are experiencing an unusually rapid expansion. This is written by The Sydney Morning Herald.

Australian scientists began to explore the area in 1928, at the same time fixing in detail the boundaries of the islands and their size on the map. In the 1970s, maps were refined using detailed aerial photography. Now researchers have also used satellite imagery. The results were somewhat unexpected.

“What is particularly interesting is that many of the islands in the Howick group are growing,” said Sarah Hamilton. “Most of the islands we explored are mostly made up of small pieces of coral.

Waves carry them to the shores of the island, laying them there. These coral deposits are “guilty” of the growth of the islands. Add to this mangrove forests, <…> some of them advance [on the sea] by five to six meters a year.”

The researcher notes that such islands formed in a similar way. At first, in their place was the sea, then the fragments of corals (after death, some of them inevitably collapse) were carried out by waves to the same points of shallow water.

Gradually, “hills of debris” began to rise above the water, and then they were colonized by mangroves. These tropical plant communities, often using stilted roots, gradually anchor and fix the coastline, making it easier to further expand islands in similar locations. After all, earlier strong storms could begin the destruction of local shores, and after their “fixation” by roots, this is much less likely.

Great Barrier Reefs mangrove islands are expanding despite the advance of the sea 2

The scientist notes that, by comparing the maps of 1928 with aerial photographs of 1974 and satellite images of our years, she revealed a serious increase in their area – especially rapid after 1974. However, satellite imagery may not accurately capture the boundaries of such islands, since mangrove vegetation often makes it difficult to find the true coastline – especially during high tide, which floods a large part of the mangrove forests. To clarify the boundaries of the expansion, Hamilton’s team deployed low-altitude, high-accuracy drones.

Oksana Repina, who participated in the research, noted: “This place is one of the most diverse and iconic ecosystems on Earth. Of course, the media headlines portray this [Great Barrier] Reef as dying or dead, but that’s an oversimplification… Let’s not write the reef off.”

It should be noted that the Great Barrier Reef has reliably existed over the past hundreds of thousands of years, including the period of the Mikulin interglacial.

At its peak, about 120,000 years ago, temperatures were two degrees warmer than today’s pre-industrial levels, and sea levels six meters higher. Obviously, Repina is close to the truth, so it’s too early to discount the reef in today’s conditions, to put it mildly.

The situation in which the islands of the Pacific Ocean, declared in the press as doomed to sinking, is actually growing, is not unique to the Great Barrier Reef.

As Naked Science already wrote , Tuvalu’s foreign minister, before the climate summit in Glasgow, also claimed that the islands of his state were disappearing under sea waters. However, he kept silent about the fact that, according to satellite images, their area, on the contrary, is growing. The mechanism of growth there is the same – the removal of material by waves, which is ahead of the rise in sea level.


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