The rebuilding of Paris’s fire-ravaged Notre Dame Cathedral is continuing apace, but new conservation concerns are being raised over the up-to-1,000 ancient oak trees needed to restore the building’s iconic spire.

Eugène Viollet-le-Duc’s 300-foot-tall original spire was erected in 1859, a wood-and-lead icon that was, somewhat ironically, the last in a long line of replacement spires that had been raised over the course of the Gothic cathedral’s 850-year life. For much of the two years since the fire that gutted the UNESCO World Heritage Site, a debate raged over whether to replace the spire as it stood or with something more modern; historic accuracy has since won out and in July of 2020 it was decided the spire would be rebuilt as it stood pre-fire. Of course, adhering to historical accuracy has brought with it a slew of new problems.

In the race to repair Notre Dame ahead of the 2024 Summer Olympics in Paris, officials are combing ancient state-owned and private forests for up to 1,000 150-to-200-year-old oak trees for the spire replacement alone; replacing “the forest,” the tangle of triangular timber supports that propped up the roof of the cathedral, will require about another 1,500 oak trees.

According to The Guardian, the trees needed for the spire must be between 20 and 36 inches wide, straight, between 26 and 46 feet tall, and must be cut down before the sap rises through the trunk in March (they missed the target this year). After being cut down, the trunks need to dry for 12-to-19 months before they can be turned into workable beams.

At the time of writing, the 85 150-year-old oaks (59 from the Villefermoy forest and 26 from forests owned by the National Forestry Office) have already been cut down and are on their way to be cut up before the drying process, according to Artnet. Although timber from Villefermoy has historically been used to erect cathedrals in the past, and many of the historic oaks used were planted with the intent to eventually use them for shipbuilding or construction, the harvest hasn’t been without its detractors. A petition with over 42,000 signatures at the time of writing is calling on the French government to reconsider, calling the plan “ecocide” and questioning the historic value of a simple reconstruction, no matter how faithful it may be to the original spire.

The slow pace of tree delivery seems like it could be a major issue for the project’s timetable, but right now focus is on stabilizing the building’s burned remains—the melted scaffolding stuck to the cathedral’s masonry was only disassembled and removed last November owing to the pandemic. Restoration work isn’t slated to begin until 2022, and on April 2, Notre Dame rector Patrick Chauvet admitted to the Associated Press that reconstruction efforts could last for “15-to-20 years.”