Slowly but surely: France’s forest assets
After Notre-Dame’s multi-secular roof timber frame was destroyed by fire last week, discussions have raised about the possibility to rebuild it identically from new lumber chosen in mainland French forests. The venerable frame, which had been built during the reign of Philippe Auguste (grandfather of Saint Louis) in the 13th century – with lumber some of which could have reached the age of 300 to 400 years, meaning they grew in Charlemagne’s empire – was composed of oak wood, one of the most common tree in Western Europe and one of the most lasting one (indeed!), with a highly symbolic value.
French forest cover is one of the largest in the European Union, with 17 million hectares (corresponding to an average of 31% of land territory, but with a high degree of discrepancy between regions), behind Sweden (28 Mha, 69% of forest cover), Finland (22 Mha, 73%) and Spain (18 Mha, 37%). The vast majority of the French forest is naturally generated (only 12% of planted forest); in Sweden, Finland and Spain, the share of the planted forest is respectively 50%, 30% and 16%. This is important as naturally generated forests are proven to host more biodiversity and provide a higher variety of ecosystem services.
About two-thirds of French forest volume is composed of hardwood species (broad-leaved trees), while Scandinavian forests are mainly softwood (conifers). In France, oak represents more than 40% of hardwood volume, from which new lumber could be extracted for Notre-Dame. About two million cubic meters of oak wood are produced for noble use (mainly building and cooperage) every year (Le Monde). Some of the oldest existing oaks were planted in the 17th century, under the direction of Louis XIV’s minister Jean-Baptiste Colbert in anticipation of the Royal Fleet’s future needs (these trees are now protected). Forest surface area is now twice larger than in the 18th century, due to the decline of wood usages (charcoal in particular).
Three-quarters of the forest is private in France. Among the remaining 4.3 Mha of forest that are public, 1.5 Mha directly belongs to the State (i.e. 9% of total France’s forest) while 2.7 Mha are communal forests (16% of total forest). This represents assets of respectively 52 bn € (private), 11 bn € (communes) and 5 bn € (State) considering 2017 average market price of 4110 € per hectare (which varies considerably, however, according to the different regions). However, estimates brought by the Chevassus-au-Louis report, which attempted in 2009 to measure monetarily all services provided by natural ecosystems in France, would raise this natural capital stock to around 440 bn €, 90 bn €, and 50 bn € respectively. These values are only rough estimates; notable differences are observed from one forest to another, starting with the type of trees (hardwood or softwood). It is also worth mentioning that public forests show a higher wood volume per hectare on average than private forests.
Among the different threats that could pose a risk to the perpetuation of this national patrimony, the temptation of increasing wood productivity is not the least, especially in tough economic times. The French forestry sector is in crisis, and the public forest administration struggles to decrease its deficit. More wood could be extracted from forests, but this is not without danger: natural ecosystems are fragile, and an increase of anthropic pressure can have disproportionate consequences, like on biodiversity.
Storms, insect infestations and droughts are the other common threats to forest ecosystems, and we may add climate change to this (especially in the Mediterranean region), as it drives all three phenomena. Forests are viewed, furthermore, as a solution to climate change: as is well known that forests play a major role in the carbon cycle with carbon sequestration, an important ecosystem service that could help to mitigate emissions. However, current sequestration rates in European forests are not sufficient to offset the enormous quantities of carbon that are emitted otherwise, and including fast-growing species to improve this sequestration would be canceled by an albedo effect, as fast-growing trees – conifers – are also darker, i.e. they have more warming effect.
Hadrien Lantremange, Natural Resources Research
Source: Beyond Ratings, FAO, Le Monde, INIGF, CNPF
 UN Food & Agriculture Organization (FAO).
 Le Monde, La forêt française est prête pour la reconstruction de Notre-Dame, 18th April 2019
 Institut National de l’Information Géographique et Forestière
 Centre National de la Propriété Forestière – Forêt Privée Française