FRANCE – Montmorency: planting the sessile oak to replace diseased chestnut trees and so protect biodiversity

Foreground: a planted plot; background: a plot to be planted ©ONF

This project is already funded!

Background & challenges

In 2018, chestnut trees in forests to the north of the Ile-de-France region were found to be dying out due to a pathogen causing the devastating chestnut ink disease. Provoked by an organism present in soil water, this disease penetrates the root system of trees and triggers rapid necrosis. The tree can then no longer take in water and becomes extremely susceptible to drought. It can die in just a few days.

The chestnut tree is an emblematic species of Ile-de-France and particularly well established in the forest of Montmorency with an occupancy rate of 70%. The damage is such that in 2018 the forest was classified as being in a health crisis. When the trees are diseased or dead, the ONF must then resort to sanitation cutting. Next, planting is carried out to restore healthy afforestation with more resistant species.

Through sanitation cutting and replanting 1,000 trees on a plot of land, the project aims to:

  • restore forest cover that is more resilient to climate change thanks to the species installed;
  • protect the habitat of deer, wild boar, foxes, badgers, endemic birds like the woodcock, amphibians, as well as many species of beetles and lepidoptera. Finally, the forest is also home to the royal fern, a species protected because of its rarity;
  • restore rainwater filtration to the forested area. The forest of Montmorency is key to tackling erosion in the region;
  • carbon sequestration in the soil, branches, and trunks. According to ONF calculations, over the long term (160 years) this project on the plot could sequester some 720 tonnes of CO2 per hectare, i.e. 820 tonnes of CO2 for this project;
  • ultimately produce timber by exploiting this forest for the next 160 years.

Project type



The inhabitants of neighbouring communes who regularly visit this forest

Number of trees

A total of 1,250 to be planted to retain 1,000 (80%) following the first thinning operation 35 years after planting

Species planted

The sessile oak, with a natural increase in the birch, whitebeam and chestnut trees (disease-free) already growing on the plot


Office National des Forêts

Planting teams from Office National des Forêts in action ©ONF

Works timeline

Beginning of December 2019: soil preparation using mechanical digger

February 2020: planting

2021 or 2022:  partition grinding if necessary

2023:  replenishing  if regrowth is under 80%

2025-2030: the first clearing operations to be every five years

First thinning operation 35 years after planting

Logging of the forested area after around 160 years

Planting partner

The territories under the wing of the Office national des Forêts (ONF) cover nearly 11 million hectares of forest, of which 6 million in French overseas departments and 4.7 million in metropolitan France. With a workforce of around 9,000 deployed across the whole territory, the ONF is responsible for the renewal and upkeep of 1,300 state-owned forests and 15,600 community forests. Managing public forests reconciles three inseparable objectives: meeting human needs by producing and harvesting timber, environment protection, and welcoming the public. The approach is based on the forest regime, which provides a regulatory framework and set of guarantees for preserving forests over the long term, while ensuring renewal of timber resources.


The total budget to be collected is 16 000€, i.e. 16€ per tree, broken down as follows:

  • Study and development of the plot: 1.41€.
  • Soil preparation : 2,56€.
  • Plants (purchase and installation): 2,43€.
  • Protection (purchase and installation): 4,10€.
  • Technical follow-up of the plantations: 2,30€.
  • A Tree for You collection, follow-up and communication costs (20%): €3.20


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