Largest French biodiversity reserve with 5,500 plant species and 1,400 animal species, Guyana is not spared by climate change.
A phenomenon that risks modifying the functioning of the equatorial forest or disrupting the reproduction of certain species such as sea turtles.
"According to projections, global warming will be by 2100 in French Guiana from +1.5°C to +4°C", indicates Ali Bel Madani, climatologist of Météo-France Antilles Guyane.
These data, from the new GuyaClimat report, revise upwards the latest estimates from Météo-France, which in 2013 predicted +1°C by the end of the century.
A rise in the thermometer with “significant” consequences for flora and fauna, already visible in green, olive ridley and leatherback sea turtles which have found a high breeding ground in Guyana.
Turtle reproduction declines
Because in turtles, it is the warmth of the nest that determines sex.
“The warmer the nest, the more females there will be.
With the rise in temperatures, we are witnessing a feminization of populations which jeopardizes reproduction,” explains Benoît de Thoisy, president of the Kwata association, which specializes in the conservation of turtles.
In ten years, lute clutches have dropped in Guyana.
From 9,516 in 2009 to 828 in 2022 according to the association.
The warming of the oceans would also be responsible.
"After the spawning season, they migrate to the convergence zone of hot and cold waters at Canada level, rich in plankton and jellyfish, in order to fatten up there", explains Benoît de Thoisy, "but, according to our data, the migrations are longer and longer because the cold waters are receding”.
Additional kilometers synonymous with exhaustion of the reptiles which start their fat stock to migrate, at the expense of reproduction.
“In the 1960s and 1970s, lutes could lay 5-6 broods per season.
Today, we are at 4-5 at the most and rather at 2-3 on average, ”adds the president of Kwata.
Tree growth decreases
In addition to wildlife, this rise in temperature is also disrupting the forest that covers 97% of Guyana.
"When the heat is high, the trees tend to close their stomata, this small opening which allows them to breathe and exchange with the atmosphere", indicates Olivier Brunaux, director of the research center at the National Forestry Office of French Guiana. .
“As a result, the trees sweat less, photosynthesize less and grow more slowly,” he says.
The reduction in growth implies a reduction in carbon storage capacity – 1.5 gigatonnes for the Guyanese forest – one of the most important ecosystem services provided by trees.
In addition, according to a study by the UMR EcoFog (CNRS), past 31°C, the humid tropical forest evolves into a dry tropical forest.
"For the moment, Guyana is rather preserved, unlike other places in the Amazon basin, in particular the Brazilian state of Roraima where rising temperatures and falling rainfall have transformed the forest which has become, at the extremes, a savanna “, according to Olivier Brunaux.
Because the other threat of climate change on the Amazon, identified by scientists, is the drop in precipitation.
The IPCC, the group of experts on the climate of the UN, estimates it at -20 to -30% by 2100.
However, to remain a humid forest, a certain threshold must not be reached.
“The real impact is less than 1,500 mm of water per year.
In Guyana, we are 4,000-5,000 mm to the east of the department and 2,000-2,500 mm to the west”, testifies Olivier Brunaux.
And still it is necessary that these rains are distributed over all the months of the year "with at least 150 mm of water per month", continues the researcher of the ONF.
Among GuyaClimat's projections: the lengthening and intensification of the dry seasons which would lead to "hydric stress, the period during which, without water, the soil reserve is empty".
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Guyana
Climate change
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