Tree hugging

Size matters! In search of Mauritius’ biggest…….

By Dr Christine Griffiths, 6 January 2023

As everyone knows, size does matter for so many things! But how do we find the largest? How do we measure it? Is it the girth or the length that makes it the biggest? And why is it so important?

Owen fired off these questions as we hiked through the forest at our newest conservation site at Providence. We went from looking where we were stepping to stumbling around as we searched for the biggest tree. But it couldn’t be any tree! Owen insisted it had to be an endemic or native hardwood!

That day, Adisha claimed to have found a strong contender. A bois d’olive, Cassine orientalis, with a circumference of 2.93m!

A joyful Adisha thinking she has found one of the largest native trees in Mauritius.

But Owen was not satisfied! We had only covered about a square kilometre, less than one per cent of the whole island, 2,040 km2. There must be larger native trees out there. We were now not only on the hunt for mature endemic trees, as part of a project co-funded by Fondation Franklinia and in collaboration with the Forestry Service, to reduce the threat of extinction of mature endemic trees, but to record the largest trees!

Five hundred years ago, native forests once covered the whole of the island. Fast-forward to today and you will struggle to find native forest, or even a native tree! Less than 2% high-quality native forest remains. And it’s rapidly disappearing!

tree mauritius comparison

Little native forest remains of the once expansive forests

There’s a high chance that the next time you are out for a forest hike, the commonest trees you will encounter are those that have been introduced by humans, either accidentally or intentionally. While not all non-natives are bad for biodiversity, those species that have become invasive are often killers. Smothering, strangling, expanding and suppressing slower growing natives.


Why size matters?

So why are we so keen to find the largest tree?

Two reasons. Firstly, like every plant, trees provide oxygen as a by-product, when they use carbon dioxide to produce sugar. Large trees produce more oxygen, store more carbon and are better buffers to climate change. Large trees also provide more microhabitats and thus are crucial for healthy forest ecosystems. Today such large trees are incredibly rare in Mauritius.

Secondly, we want and need to raise awareness of just how important are our native trees and forests. Plants are the life-support system for pretty much all of the island’s native and endemic flora and fauna, ranging from orchids, snails, birds, butterflies and crickets. The list is endless! Our wildlife is knocking on the door of extinction. More needs to be done and we are running out of time. Only a handful of organisations manage forests to control invasive plants, such as Ebony Forest, National Parks & Conservation Services, Forestry Services and Ferney Valley. And it’s not enough. Weeding is costly and requires long term commitment as invasive weeds are relentless. Native plants have to be reintroduced!


Identifying a champion

Did Adisha discover one of the largest native trees in Mauritius? According to Dr Vincent Florens of the University of Mauritius there are much larger natives in Mauritius such as bois colophane, Protium obtusifolium, with a circumference of 4.95 m. Adisha’s just going to have to keep looking!

The easiest way to find the largest tree is to measure tree circumference. To standardize measurements, scientists take these measurements at breast height, set at 1.3 m above the ground. The diameter of a tree is generally correlated with its height. Taller trees need larger trunks to support their mass.


World Titans

The tallest tree in the world is Hyperion, a majestic giant sequoia in California’s Sequoia National Forest, peaking at 115.92 m tall. The Mexican town of Santa María del Tule hosts the widest tree in the world, El Árbol del Tule, a cypress tree with a diameter of 11.62m. Just for some context, it would have a circumference of 36.5 m!! The title for the World’s largest tree, based on volume, is General Sherman, another sequoia giant!

Alas, but what about Mauritius? Who are our giants?


Intrepid nature lovers, find that giant

No one knows! That is why we are calling for everyone to find the largest native tree!

Have you spotted a large endemic or native tree? Perhaps it is the largest? Simply take a photo of yourself with this fine specimen and make a note of where you found the tree. If you have a smart phone turn on your gps details and record these. Send us pics of your tree giants and we’ll share them with you nature lovers. Remember, we are after those natives!


Small acts

of Kindness can
go a long way