The largest trees on the planet fade

Deforestation and climate change are ending the oldest examples of redwoods, giant ash or baobab


MIGUEL ÁNGEL CRIADO

22 APR Some of the oldest and largest trees in the world were already on the planet when most humans lived literally. in the Stone Age. However, a range of human actions, such as logging, ecosystem degradation and now climate change are killing the older redwoods, eucalyptus trees 100 meters or trees as magical as the baobab.

The worst thing is that there are no longer any conditions for younger specimens to reach the height and age of their ancestors.

Although there are many species of ancient trees, a few grow for centuries to reach the 50, 100 and even 115 meters that exceed some red sequoia.

There is no well defined category of what botanists call LOT, Large Old Trees. There is also no minimum height or span to determine what a large tree is.

An objective fact is the central character they play in their ecosystem. This is why the LOT are the two species of redwoods that grow on the west coast of the USA, the mountain ash (Eucalyptus regnans) that grows for 400 years until the 100 or more meters or the Petersianthus quadrialatus, a species of pink wood that grows in the Philippines.

But also old and large trees are spruces of more than 50 meters in the old forest of Bialowieza (Poland) or the African baobab that in some species reaches 30 meters in height and more than 10 in circumference. Almost all of them are in retreat.

In Yosemite National Park (California, USA), home to redwoods and other giants such as American Royal Pine, which can reach 70 meters in height, another research showed in 2009 that density by hectare of these large trees had been reduced by 25% since the 1930s. While the world's tallest floral tree, the Australian mountain ash, will go from a ratio of 5.1 trees per hectare that had at the beginning of the century only 0 , 7xHa in 2070.
"The decline has accelerated in many ecosystems," says National University of Australia's David Lindenmayer. This researcher, specializing in large trees, recalls that these species are particularly susceptible to drought, but have also suffered and are still suffering from unsustainable logging in many areas.

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"In some northern European ecosystems, there has been an increase, but they started from very small populations," he adds.

The new threat is global warming. "Climate change brings climatic conditions to levels outside the normal range of the ideal niche for tree growth and development," explains Lindenmayer. "For example, reducing rainfall in south-east and south-west Australia will cause these large and old trees to not reach their height and size again. In other cases, conditions when the first germination occurred 500 years ago so different nowadays that they will not be able to re-germinate in the same areas where they grow now, "he adds.

At least two species of baobabs grow in Madagascar will disappear before the end of the century.Gavinevans / Wikimedia Commons Deforestation of both large and small trees has already put at risk the survival of at least 500 species of mammals, birds and amphibians so far this century, according to a study involving BirdLife But the relevance of these almost eternal trees goes beyond ecology.

Many of them have fulfilled social and even religious missions for the human communities that have lived under them. "We believe that recognizing LOTs as part of human identity and its cultural heritage is essential to address the issue of its decline throughout the world," he said.

One of the authors of that paper, Uppsala University researcher, Malgorzata Blicharska, says that hardly anything has been done since then.

If these measures were explicitly incorporated, "conservation could be improved. of the LOT " comments.


But the task is not simple. Right now, in the heart of Europe is preparing a large felling of ancient trees, perhaps millennia, in Białowieża, one of the last remaining primeval forests on the continent. "Even this World Heritage Site is under pressure, with foresters who want to cut old European spruce [a conifer] due to a plague of bark beetle, something that is strongly opposed by both communities scientists and conservationists at local and international level, recalls Professor of the Swedish University of Agricultural Sciences, Grzegorz Mikusinski, co-author of the article on the social and cultural dimensions of LOT.

On Earth Day, Lindenmayer and his colleague from James Cook University (Australia), Bill Laurance, publish in Trends in Ecology & amp; Evolution a series of measures that would have to be taken to save the LOT. But as Laurence says, "We have to make sure we think long term, to coincide with the way these trees have existed for thousands of years."

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  • Adam Floyd