Frequently asked questions

With climate change, we observe an increase in frequency and intensity of disturbances causing majors forest mortality (droughts, forest fires, pest outbreaks…). Those are expected to further increase over the next decades, in Europe and all around the world.

Climate change causes a form of South-to-North climate migration. This pushes species, both animal and plant, to adapt or move in order to “follow” the conditions that enable their development. The climatic niches of the different tree species will be modified to a greater or lesser extent in north-western Europe.

The rapid pace of change today places severe constraints on the adaptation and migration of tree species. Estimates of the migration rate required for species to keep pace with climate change are commonly higher than 1000 m a year, which is much higher than the capacity of trees to migrate. Indeed, it is thought that tree species dispersal capacities allow them to migrate less than 500 m a year (and often less than 100 m a year).

In order to prevent the potential collapse of certain species' populations, and to maintain forests and the services they provide (wood production, carbon storage, water regulation, etc.), this movement can be encouraged by man. This is known as assisted migration.

Assisted migration is a general term that encompasses a variety of different potential actions, which have substantial differences in terms of risk, ecological implications, and policy considerations. Here are some of the commonly used terms that distinguish between different forms of assisted migration:

• Assisted population migration (also assisted genetic migration or assisted gene flow) – moving seed sources or populations to new locations within the historical species range. Example: planting in Belgium of sessile oaks (Quercus petraea) from Southern France.
• Assisted range expansion – moving seed sources or populations from their current range to suitable areas beyond the historical species range, facilitating or mimicking natural dispersal. Example: planting in Belgium of maritime pines (Pinus pinaster)
• Species introduction - (also species rescue, managed relocation, or assisted species migration) – moving seed sources or populations to a location far outside the historical species range, beyond locations accessible by natural dispersal.  In other words, species introduction happens when species are translocated beyond physical barriers that could not be crossed naturally (oceans, deserts, …) Example: planting in Belgium of liquidambar (Liquidambar styraciflua)

In the context of MigFoRest, only the 2 first forms of assisted migration are experimented.  

Within the MigFoRest framework, only movements of origin and species from the European continent will be considered. This is a stricter vision of assisted migration, in which only movements that might occur naturally in response to climate change are included. Intercontinental movements are excluded. The species proposed are indigenous to the target region (e.g. sessile oak  (Quercus petraea)of southern provenance) or to regions close to it (e.g. Hungarian oak : Quercus frainetto). As these species have evolved in the presence of a complex of European organisms (fungi, bacteria, insects, etc.), the risks (invasive and sanitary) associated with such introductions are limited. The term “introduction” is used in this document to describe these intra-continental movements. This approach should not be confused with the introduction of totally new species.

Typically, good candidates for assisted migration are species with a wide distribution in Europe, with populations present in southern regions in particular, and certain provenances of which are therefore “pre-adapted” to the climatic conditions expected here, such as sessile oak (assisted provenance migration, see above). The same applies to species found only in latitudes lower than ours and likely to migrate naturally northwards, such as downy oak (Quercus pubescens).

Thus, only European species will be planted.

The ten selected species belong to four genera:

🌲 Abies (firs) : ​silver fir (A. alba), Greek fir (A. cephalonica), Spanish fir (A. pinsapo);​

🌳 Quercus (white oaks) : sessile oak (Q. petraea), pedunculate oak (Q. robur), pubescent oak (Q. pubescens);

🌳 Tilia​ (lime trees) : small-leaved lime (T. cordata), large-leaved lime (T. platyphyllos);

🌳 Sorbus (rowans) : wild service tree (S. torminalis), ​service tree (S. domestica).

These are the species from which genetic diversity will be studied and seedlings will be produced by the project partners. 

 In addition to these, other species could be planted, depending on their availability in the nurseries: Hungarian oak (Quercus frainetto), Pyrenean oak (Quercus pyrenaica), zean oak (Quercus canariensis), silver lime (Tilia tomentosa), whitebeam (Sorbus aria), Oriental beech (Fagus orientalis), etc.

 🌍 All of these species originate from Europe.

• Increase the resistance and resilience of our forests by enhancing the genetic diversity, particularly in currently vulnerable stands
• Assisted population migration and assisted range expansion may not add much cost to existing practices of forest regeneration for species that are routinely planted
• Provenance trial data are available for many widespread, commercially valuable tree species, which will help managers make informed decisions about the performance of seed sources from outside their local area
• The genetic diversity of seed orchards can be controlled or increased to provide a suitable seed source for commercially valuable trees
• Assisted migration can help maintain crucial ecosystem functions (wildlife habitat, carbon sequestration, etc.), particularly when local species are already declining or are anticipated to decline in the future