Exceptional floods, repeated droughts, gardens in pain... Threatened by climate change, the Loire Valley châteaux are "navigating by sight"

In recent years, "the sharp decline in the flow of the Loire is not without consequences for the emblematic châteaux bordering the river," warned the Climate Action Network (RAC) in 2024, in a regional mapping of the impacts of the climate crisis in France and its repercussions on heritage.

The Château de Chenonceau, for example, whose foundations are immersed in the Cher, the main tributary of the Loire, "is particularly exposed to climate change and variations in water regimes," explains the chief architect of historic monuments, Étienne Barthélémy, to AFP.

"If the wooden piles used for foundations are sometimes exposed to the air and sometimes in water, the natural rot that sets in is more significant" and weakens them, warns Étienne Barthélémy, citing the notable consequences of the long drought of 2022.

Conversely, during periods of particularly heavy rain, such as this winter, "a strong flow of the Cher can 'wash away' the masonry and create significant pressure on the pillars", which already bear "scars from the impacts of tree trunks hitting them".

As you travel up the Loire, all the Loire châteaux, priceless jewels and must-sees for tourists from all over the world, are ultimately threatened by the direct effects of climate change.

"Gardens to rethink"

The Château d'Azay-le-Rideau, a Renaissance jewel built under the patronage of François I, also carefully monitors the water level of the two branches of the Indre which surround it and decreases from year to year.

The high temperatures have also increased the presence of invasive algae around the building, forcing teams of gardeners to intervene in the ponds every week to limit their proliferation, instead of the usual once a month.

"To manage a historic monument like this, we're constantly navigating by sight, trying to invent solutions as problems arise," admits its administrator, Benoit Grécourt.

A point of view shared by the mayor of Amboise, Brice Ravier, who was until recently concerned about the risk of landslides at the town's royal castle, where "between 6,000 and 9,000 tonnes of earth threatened to collapse" at the beginning of February, a danger "directly linked to the heavy rains" of last autumn.

This major disruption led to the evacuation of more than 50 people, according to the mayor, who was "reassured that everyone was able to return to their homes at the end of June," following a €2.5 million consolidation project.

Another major consequence is that the monuments also lead to reflections around their parks, most of which were designed in the 19th century.

"Major project"

As with the French gardens of Chambord, challenges arise in Azay-le-Rideau, where "the park designed in the 19th century brings together a whole variety of plants and trees that do not tolerate these climatic disturbances well," concedes Benoit Grécourt.

Work "without betraying the original identity" of the places: replacing certain plant species with others that require less water, represents one of the main avenues.

These changes and anticipated achievements involve very significant investments, estimated at "10 million euros for restoration work" for Chenonceau alone, according to Étienne Barthélémy.

Especially since even before the restorations begin, the necessary very expensive electronic studies are not yet included in the estimated cost of the work.

"Over the centuries, old buildings have shown astonishing adaptability, resilience and solidity, but today they are in poor condition," explains Étienne Barthélémy, ensuring that any "alarmism" is avoided.

But "a joint reflection that would mobilize specialists, the political world probably, and patrons" should be conducted, he suggests, to tackle this "very large national project."