Close to half of Europese tree species are threatened, according to a recent report by the IUCN, the groupin charge of the so-called ‘species red lists’. Causes of this dramatic number? Ongoing forest cutting of course. Yet, most importantly and rather surprisingly: invasive species topped the list of suspected culprits.

Horse chestnut: early autumn for the species all over Europe

Both invasive deseases (for example the horse-chestnut leaf miner, a little moth living in the leaves of the chestnut) and invasive tree species (like the American cherry, ruler of the forest understory) are threatening our native trees. Once again, this highlights the critical impacts of our diversity on the move.

Largest problems are in southern Europe: there, we find the highest amount of threatened tree species, among others due to the much higher tree species diversity in the south, especially in mountain regions. Additionally, however, important knowledge is lacking on many of these southernmost species, making their future particularly hard to predict.

Young beech seedling (Fagus sylvatica). Invasive tree species can cause fierce competition for the native tree seedlings (yet for now, the beech is safe).

So what to do now? More space for forests, and aiming for diverse, natural forests will be key. Botanical gardens can also help conserving endangered genotypes, while we frantically keep working to improve the knowledge of our most threatened tree species.

I got interviewed about this report by our local newspaper recently (here, yet in Dutch and behind a paywall), a great opportunity to spread these important warnings to the broader public.