Forty-Two Thousand Trees
About 42,000 plane trees lined the Canal du Midi, and a fungus that reached Europe in a wartime packing crate is killing every one of them. The replanting is deliberately mixed, because the avenue's beauty and its vulnerability were the same fact.
The Canal du Midi was finished in 1681 and the trees came much later. Planes were planted along both banks through the nineteenth century, in ranks, for 240 kilometres between Toulouse and the Étang de Thau. They were not decoration. Roots bind a bank that is otherwise loose earth, and a closed canopy over the water slows evaporation on a waterway that has no river feeding it and has to be topped up from a reservoir in the mountains.
There were about forty-two thousand of them. Voies navigables de France, the state body that runs the canal, expects to lose all of them, and more than thirty thousand have already come down. The disease was identified on the canal in 2006, near Villedubert in the Aude, and there is no treatment, no resistant spray and no way to save an infected tree. The only response the law permits is a chainsaw.
A fungus that arrived in a crate
Chancre coloré is caused by Ceratocystis platani, a fungus native to North America, where the local planes have lived with it long enough to tolerate it. The tree planted along the canal — a hybrid with one American parent and one oriental — has not. It is generally accepted to have crossed the Atlantic in the packing cases of American military supplies at the end of the Second World War and to have established itself first around Marseille, from where it spread inland over sixty years.
The canal is close to a perfect delivery system for it. Plane trees planted in a line at close spacing graft their roots together underground, so the fungus walks from one to the next without ever surfacing. It also travels in water, which the canal supplies in quantity, and on contaminated steel — a blade that cuts an infected trunk and then a healthy one has done the work. When a case is confirmed, the tree and its neighbours within a set radius come down, the timber is burnt or chipped and incinerated on the spot rather than carted away, and the stumps are ground out.
What a monoculture costs
The nineteenth-century planting was one species, repeated. In places it was one species propagated from very few individuals, which is closer to a single organism spread over hundreds of kilometres than to a forest. That is exactly why it looked the way it did — the uniform height, the matched trunks, the tunnel of light that every photograph of the canal is taken in. It is also why a single pathogen can take the whole thing.
The avenue was planted as one idea repeated forty-two thousand times. That is why it was beautiful, and it is why it is going.
Who pays for an avenue
The replanting is deliberately unlike the original. A resistant plane hybrid, Platanor ‘Vallis Clausa’ — the only plane clone French law allows to be planted in an infected zone — goes in on some stretches, but so do oaks, limes, maples, nettle trees and white poplars, mixed rather than uniform, so that the next arriving disease can only take a share. The cost of felling and replanting the length of the canal has been put at around €200 million spread over two decades, which VNF's ordinary budget does not cover; a public subscription, Replantons le Canal du Midi, has been running since 2013 to close part of the gap.
The canal has been a UNESCO World Heritage Site since 1996, and the listing is for the engineering — Pierre-Paul Riquet's water supply from the Montagne Noire, the summit at Naurouze, the reservoir at Saint-Ferréol, the tunnel at Malpas that was the first ever dug for a canal. None of that is the trees. Heritage status raises what people expect of a place without providing the money to meet it, and the trees are what visitors came for.
What is actually there now
Long open stretches with stumps ground flat and a view across vineyards that nobody riding here twenty years ago ever had. Then a kilometre of mature canopy that has so far escaped, dark and ten degrees cooler. Then young trees at three metres with guards around them, planted close and staked, which will be an avenue again around 2070 for somebody who is not you.
The practical consequence is heat. On the felled sections in July there is no shade at all between one village and the next, the canal water is not drinkable, and the towpath holds the temperature. Ride before ten. The compensation is that with the screen gone you can finally see what the canal is: a contour line drawn across Languedoc by a salt-tax collector who worked out where the water was before he worked out where the boats would go.