Source: French to English Tester Published on: 2026-04-28
Source: The Conversation – in French– By Estelle Razanatsoa, Junior Research Fellow, University of Cape Town
Madagascar is home to seven species of baobabs, six of which are found nowhere else on the planet. Many of these trees are over 1,000 years old. These ancient trees have become symbols of Madagascar itself. They also provide a wealth of information for climate science.
Imagine these trees as filing cabinets containing the history of the climate. Each year, when a tree grows, it forms a new ring, and inside this ring are chemical footprints that reveal the amount of rain that fell that year.
These archives could provide the company with the information it needs about the climatic history of Madagascar. But until now, this information was hidden in the trunks of trees.
We are a team of applied paleoecologists and climatologists who have made it our mission to providethe very first recordingprecipitation from tree rings reconstructed from isotopes present in the rings of Madagascar baobabs.
Isotopesare different forms of the same chemical element that have the same number of protons but a different number of neutrons in their nucleus. Baobabs absorb carbon dioxide, which contains three isotopes of carbon: carbon 12 (light, most common), carbon 13 (heavy, stable but less common), and carbon 14 (rare and radioactive).
The chemical process is elegant: during dry years, trees absorb more carbon in its heavier form, because they close their stomata to conserve water, which leads to increased absorption of ¹³C compared to normal conditions. During wet years, this signal decreases. By linking enough of these signals and combining them with theradiocarbon datingwhich makes it possible to determine the age of the trees, we obtain a natural rain gauge covering several centuries – the first of its kind ever produced for Madagascar.
Our research aimed to enrich the paleoclimatic archives of Madagascar. These are records of temperature, precipitation, and climate covering centuries and millennia. When combined with other paleoecological indicators such as pollen, they help understand the functioning and evolution of ecosystems over hundreds of years.
Read more:
How bats and moths preserve Africa’s baobabs
Most of Madagascar’s paleoclimatic archives are found in mineral deposits such asspeleothems,stalagmitesand sediments, and to date, they are few in number.
Although the scientists havealready usedthis method for establishing a rainfall record over 1,000 years from baobabs in South Africa, this had never been attempted in Madagascar.
Our goal was not solely academic. This type of long-term data has a direct and concrete interest for biodiversity conservation, land management, and strengthening resilience to global warming.
From the field to the laboratory
We collected samples from four large baobabs in southwestern Madagascar, the driest region of the island. We inserted a long auger to extract samples from their core. This operation did not damage the trees. The hole was then sealed with a sealing product to prevent any deterioration caused by insects or fungi.
We took subsamples along the entire length of each core in order to analyze the isotopes at different times. More than 2,000 samples were sent toLaboratory of the Mammal Research Institute of the University of Pretoriafor isotopic analysis, and radiocarbon dating was carried out atiThemba LABS. This allowed us to reconstruct a continuous record of precipitation dating back to the year 1300 – more than 700 years of climate history, recorded in the wood.
These data tell a dramatic story. The southwest of Madagascar experienced its wettest period between 1350 and 1450. This was followed by a prolonged and severe drought from 1600 to 1750. From 1750 to today, the southwest of Madagascar has experienced a long-term trend of decreasing precipitation.
We did not stop there. We also collected sediment samples and analyzed charcoal deposits, pollen grains, and isotopes preserved in the nearby wetlands. These too are natural archives that trace changes in fires and vegetation over the same period. We compared them with the samples taken from the baobabs — and something important emerged.
Humans and climate have transformed Madagascar
When comparing the rainfall data from wet and dry periods obtained from baobabs with the pollen and charcoal samples we collected, it revealed that evergreen and deciduous trees had decreased due to drought, and had been gradually replaced by grass over time. Human agricultural practices contributed to maintaining grass-dominated landscapes through fire and clearing.
In other words, we discovered that landscape changes in southwestern Madagascar were not caused solely by humans or the climate. Drought and human activityhave jointly reshaped the territory.
We also noted that, remarkably, the landscape proved resilient. As precipitation decreased, drought-adapted plant species took over from water-demanding species. Humans (who are thought to have settled in Madagascar about 2,000 years ago) also abandoned hunting and gathering to embark onlivestock farming and rice cultivation, except for the Mikea communities who have adoptedseasonal practicesin the field of agriculture and hunting-gathering.
This shows that populations have actively found new ways to survive increasingly unpredictable rains inadaptingtheir livelihoods to the evolution of the landscape.
What this means for Malagasy people today
This study seems to be the story of an isolated island, but its implications are immediate and global.
By precisely determining when the driest region of Madagascar was humid, dry, and everything in between over a period of 700 years, scientists now have a new solid reference base to assess what could happen with current climate change.
Our discoveries about the baobabs, combined with pollen and charcoal samples, have made it possible to create a picture of the vegetation cover of southwestern Madagascar over the centuries. The use of this long-term data (paleoclimatic, vegetative, and charcoal data) across the entire island has contributed toexisting researchwhich refute the colonial narrative that Madagascar was entirely forested before humans settled there and destroyed the forests. On the contrary, our results also show the presence of sparser vegetation and indicate that the populations and the landscape adapted together to climate change.
What to do next
Our previous researchhave provided scientists and governments with the necessary information to understand how ecosystems might respond to global warming and how populations might adapt their livelihood strategies during periods of drought.
This new study shows that there is a deep connection between human societies and the natural world. Strengthening resilience to climate change today means understanding how this relationship has developed over centuries, not just decades.
This will enable integrated conservation and livelihood strategies to rely on climate data, and for communities to obtain the support they need to continue adapting and to find new and different ways to survive in a warmer and drier climate.
Our study will be combined with others conducted across Southern Africa, linking data from Madagascar with those from Botswana, South Africa, and elsewhere. This will help scientists create a complete picture of the regional climate.
This research must feed into policies. Long-term ecological data of this type are directly relevant to global objectives in the field ofclimate action, biodiversity protection, of poverty reduction and international scientific collaboration. The past has much to teach us – if we take the time to decode and read it.
Estelle Razanatsoa benefits from funding through the doctoral scholarship of the Faculty (University of Cape Town, ER.) 2015-2018 and from the project of the Applied Centre for Climate and Earth Systems Sciences (ACCESS NRF UID 98018, ER), the consortium accredited by the University Research Committee (URC) of UCT, a junior research fellowship (2023-2026) and additional COVID-19 related assistance from the URC of the University of Cape Town, 2019-2020. These funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Lindsey Gillson benefited from funding from NRF/SASSCAL (Southern African Scientific Services Centre for Climate Change and Adaptive Land Management, grant number 118589, LG), the NRF/African Origins platform (grant number 117666, LG), and the competitive NRF program for rated researchers (grant number 118538, LG). These funders had no role in the design of the study, data collection and analysis, decision to publish, or preparation of the manuscript.
Malika Virah-Sawmy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
–ref. The baobabs of Madagascar hold 700 years of climate secrets: what they reveal –https://theconversation.com/the-baobabs-of-madagascar-contain-700-years-of-climatic-secrets-what-they-reveal-281371