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10 févr. 2023 · Cette espèce est en danger d’extinction, et une étude publiée en 2021 a démontré que le changement climatique pourrait provoquer un déclin conséquent de son habitat d’ici à la fin du siècle. Le tronc de l’arbre présente des signes évidents de dégradation et pourrait donc bientôt tomber.
23 mai 2024 · 23 mai 2024. Les scientifiques ont résolu le mystère de l'origine des anciens baobabs. Selon des études d'ADN, ces arbres emblématiques sont apparus à Madagascar il y a 21 millions d'années. Par...
3 déc. 2020 · Parmi les 9 espèces de Baobabs, trois figurent sur la liste rouge des espèces menacées de l’UICN (l’Union Internationale pour la Conservation de la Nature) : Adansonia suarezensis, Adansonia Grandidieri et Adansonia Perrieri. Ces baobabs pourraient être rapidement en danger critique d’extinction.
Selon les auteurs, le point d'origine le plus probable pour la souche initiale est bien Madagascar. Baobabs à Madagascar. Crédit : Sheng-Wei Wang. Après 20 millions d'années, lors d'un évènement...
- Overview
- An island of rare and threatened species
- A new climate for an old habitat
- Traveling trees could survive
- Is the baobab doomed? Not necessarily.
Photos reveal the beauty and threats facing the island country's famous landscapes.
The world’s rarest baobab species is Adansonia perrieri, seen here growing in the Ankarana Special Reserve, a protected forest in northern Madagascar. Scientists estimate only around 200 trees from these species remain in the wild. They are threatened by climate change and may be at risk of going extinct in its habitat in the future.
If you visit the southwest corner of Madagascar, you might find a tree so old its name is Grandmother. She has three stems, fused together, so that her trunk resembles a massive rounded pot rather than a solitary sentinel. The oldest stem dates to A.D. 1600, meaning it took root a few decades before Atilla the Hun launched his rampage.
Grandmother is a baobab tree, one of a species beloved worldwide not only for its longevity but also for its distinctive crown: a tangle of scraggly branches extends from the trees' top like electrocuted hair. Or, less flamboyantly, like misplaced roots. In creation myths, the baobab is known as the tree the gods planted upside down.
“When you’re close to the trunk, you feel something powerful,” says William Daniels, a photographer who traveled through Madagascar’s forests to capture the stunning images of the baobab’s mystic charisma that appear with this story. “It’s some good energy.”
But baobabs are in trouble, potential victims of the warming globe. Scientists sounded the alarm more than five years ago, when they investigated why some of the oldest and largest baobabs in southern Africa had died. In subsequent studies, scientists found these long-lived mammoths are vulnerable to climate change and predicted that four of the world’s baobab species could become extinct by 2021. That includes Grandmother, one of the Malagasy species.
Baobab trees are native to sub-Saharan Africa and Australia, where a single species can be found, and baobabs have been introduced to India, South America, and zoos and gardens around the world.
But their presence in Madagascar is crucial.
The island has some of the richest biodiversity in the world. Once part of the African continent, Madagascar became an island more than 80 million years ago, and lies off the coast of Mozambique in the Indian Ocean. Ninety percent of the plants and animals that developed over eons of isolation are found nowhere else on Earth today. Of the seven baobab species on the island, six grow only on Madagascar.
“That’s one of the most amazing things about the Malagasy baobabs,” says Nisa Karimi, a botanist and evolutionary biologist at the University of Wisconsin, Madison. “One species occurs all across continental Africa, and then you get to Madagascar, and you have six.”
Madagascar’s wealth of baobabs is due, in part, to its diverse geography. The island, comparable in size to California or Sweden, has wide ranges in elevation, and networks of impassable rivers that create distinctive ecosystems where trees, mammals, reptiles, and flowers must find a niche.
Like baobab trees, thousands of the island’s plants and animals face environmental threats. Tortoises, chameleons, and periwinkle flowers are among the island's threatened species.
Complicating the picture for the baobab’s survival is a host of other man-made threats— including entrenched poverty in one of the world’s poorest countries, which can drive deforestation, as farmers search for more arable land. In the last 20 years, the country has lost nearly a quarter of its tree cover, primarily to logging, according to a recent study published in Science outlining threats to Madagascar’s biodiversity.
To provide further protection to the country’s biodiversity, the study’s authors suggested a series of steps, including more conservation, expanding protected areas, reforming agricultural practices, and addressing social issues that contribute to tree loss. A case in point: The drought over the past two years in southern Madagascar also produced a famine. At the same time, eastern Madagascar endured record rainfall that resulted in flash flooding. Both drought and extreme rainfall are predicted to become more common on the island, and the country lacks the resources to respond to worsening weather disasters.
As the changing climate causes rising temperatures and recalibrates rainfall patterns, trees all over the globe are on the move. In temperate regions, trees have begun migrating toward the poles to find cooler places to grow.
When scientists modeled how rising temperature and changing rainfall patterns could affect Madagascar’s baobab forests, they predicted that their habitat would shrink over the next century. Baobabs in the north would need to migrate even further north to find suitable growing conditions, but they may be out of luck. As they reach the northern coast, they’ve nowhere else to go. Scientists concluded that some of Madagascar’s northernmost baobab species could disappear by 2100.
“We know that climate change will change a lot of the island,” says Ghislain Vieilledent, an ecologist for CIRAD, a French research center, and co-author of the research, published in Global Change Biology 2021. “We don’t know precisely what will be the outcome, but we know the change will be profound, and the biodiversity will be profoundly affected.”
The worst-case climate scenario used in Vieilledent’s model is far from certain. It correlates to 4.9°C of warming by 2100, far above the U.N.’s goal of keeping warming below 2°C, but it shows the potential of climate change at its most deadly.
In addition to working with local communities and creating protected areas for baobabs, scientists are also stockpiling baobab DNA. Scientists are collecting bits of baobab genetic material in hopes of finding certain traits, like drought tolerance, that might be bred into future trees.
Karimi, the University of Wisconsin botanist, says certain baobabs could adapt to new conditions, such as saltier water or drier landscapes. She and her colleagues are searching for a diverse collection of baobab seeds to preserve the trees that have the best chance of bringing forests back to life in a changing world.
“We make sure we’re collecting seeds for reforestation under dramatic climate changes,” she says.
William Daniels works on long-term documentary projects, with an interest in people’s search for identity and the consequences of climate change. His project on baobabs is ongoing.
Selon une nouvelle étude publiée dans Global Change Biology, quatre des sept espèces de baobabs présentes à Madagascar pourraient disparaître d’ici 2100. En cause pour trois d’entre elles : l’augmentation de la saisonnalité, soit les variations climatiques au cours de l’année.
14 sept. 2021 · Madagascar. L’impossible adaptation des baobabs de Madagascar au changement climatique. Quatre des sept espèces présentes dans l’île pourraient ne pas survivre à l’augmentation de la saisonnalité...
