What role can the French forestry and timber sector play in attenuating climate change?

“Make our planet great again”… The French forestry and timber sector is already making a major contribution to the fight against climate change, which was relaunched by this slogan from the French President, Emmanuel Macron, on 1^st June following the announcement by the US President that his country would be withdrawing from the Paris climate agreement. Carried out by INRA in collaboration with IGN (National Institute of Geographic and Forest Information), this study focused on how the forestry and timber sector as a whole could pursue, or even increase, its contribution, by simulating the effects of several scenarios between now and 2050. These were mainly based on more or less active forest management methods and on how much timber is harvested each year to feed the sector and participate in developing the bioeconomy. These scenarios were also subjected to the effects of climate change and to series of random events such as storms, fires or pest invasions, etc.

Whichever scenario was applied, the forestry and timber sector demonstrated a carbon storage capacity which remained high and could even increase. Although limiting in situ carbon stocks to some extent, the intensification of forestry could participate in efforts towards attenuation through the greenhouse gas (GHG) emissions avoided by the use of wood-based materials or energy rather than competitor products from sectors emitting more GHG. For this reason, it improved the resilience of the sector in the event of crises: climate, fires, storms or pest invasions.

The forestry-timber sector considered as a whole

This study counted up all the carbon stored by forests and timber products, as well as the emissions avoided by using wood instead of competing fossil-based materials or energies, taking account of the forestry-timber sector as a whole. It covered all forests in mainland France available for the production of timber, the industries processing timber products and the social actors contributing directly to this chain of primary production and processing.

An extensification or intensification of forestry: the issues under debate

Three forest management scenarios, the effects of which were simulated at the horizon of 2050, were envisaged during this study:

• An "Extensification" scenario under which current harvest levels would be maintained, thus reducing removal rates, and where actors would be more passive with respect to climate change, counting on the adaptive capacities of forests;
• A "Territorial dynamics" scenario, under which current removal rates would generally be maintained, thus increasing intensification;
• And finally an "Intensification plus replanting" scenario which would combine the removal rates of all areas where this can be envisaged with a deliberate replanting policy targeting 500,000 ha over ten years, in order to replace stands with low yields or in a sylvicultural impasse with new, more productive plantations.

Whatever the scenario, the results showed a probable increase in the role of the French forestry and timber sector in attenuating greenhouse gas (GHG) emissions between now and 2050 (a near horizon for forests). In a different manner depending on the scenarios, this role would combine the carbon storage capacities of the forest ecosystem and the substitution effects limiting GHG emissions permitted by the use of wood products. However, the first and more favourable effect of the "Extensification" scenario might be limited by the effects of the ageing of current stands on the global productivity of the forest. The second effect, more in favour of the "Intensification" scenario, might be accentuated if its uses and related technological evolutions set wood apart from its competitors even better than today because the latter generate more GHG, as soon as the benefits of the replanting plan would start to be felt (after 2050).

To these management scenarios the study added an increase in the effects of climate change which, although it would have a marked impact on the evolution of this resource would only slightly limit growth in the use of wood products, a factor which would amortise the negative effects on carbon storage by the ecosystem.

Changes to the climate might also favour the onset of crises, and the scientists envisaged three types. Fires occurring after a period of drought (even of the severity seen in 2003) would not have an effect on the global carbon balance of the sector at a national scale. Severe storms (such as Lothar and Martin in 1999) followed by a cascade of risks (attacks by bark beetle on conifers, fires, etc.) would at least temporarily cause a reduction in the forest carbon sink that would only partly be compensated for by an increase in dead trees, the storage of timber products and substitution effects. Finally, several types of pest invasions were envisaged: attacking all types of oak or just common oak, or just maritime pine. The simulations demonstrated that pest invasions would cause as much damage as storms, but over longer periods of time. It is under this latter scenario that the forestry and timber sector would be less able to compensate for the losses.

Whatever the scenario (rise in temperatures, storms, pest invasions), it nevertheless remains that the carbon storage capacity of the sector between now and 2050 remains positive, and would increase under active forest management.

The intensification of forestry would preserve heritage forests…

The "Intensification" scenario included a replanting plan to cover 500,000 ha in ten years, as suggested in a report from the CGAAER (2015). That study focused mainly on a detailed analysis of the feasibility of such a policy with respect to the forested areas that might be concerned. It was able to identify areas that were both accessible, suffered from poor yields or were in a sylvicultural impasse from an economic point of view, as well as the different high-yield species for which grain stocks would be available within the necessary timeframe: some ten species were thus identified. It thus excluded heritage forests from the start, although they also represent major challenges in terms of biodiversity and leisure.

… but require major collective efforts

The economic analysis conducted using the FFSM model developed by the Forest Economics Laboratory (INRA-AgroParisTech Joint Research Unit, LEF) in Nancy nevertheless revealed economic obstacles to the intensification envisaged under the third scenario, or even under the second. It would prove difficult and costly to the public purse to increase current removal rates because this would require major incentives to both drive consumers to purchase wood-based products and to encourage forest owners and industry towards intensification. Despite the efforts required, the economic gains for the sector could be considerable. Consumers, owners and processors would therefore benefit greatly from these changes.

After the 2050 time horizon

This study on the forestry and timber sector and climate change used the MARGOT resource model developed by IGN and identified opportunities to improve such models. The objective may now be to exceed the horizon of 2050 in order to provide forest managers with greater foresight regarding their long-term activities.