We are reforesting Europe with trees that will not survive until 2100 | Climate

One of the great challenges of forest management is time: trees are long-lived living beings and, with the climate crisis, perhaps a species that is adapted to the conditions of the present will not survive those of the future. A scientific study, published this Monday in the journal Nature Ecology & Evolutionreveals that the tree species that we consider suitable today for reforesting Europe may not survive until 2100 due to changing climate climate.

Scientists assessed the distribution of 69 native tree species across Europe – including oak, pine and willow – in both virgin and reforested forests. To predict the behavior of these species in the future, the authors developed a model capable of estimating their survival capacity until the end of the century. The conclusions of the study indicate that some species may be threatened even in a scenario of climate change moderate.

“The main conclusion is that climate change will have a strong impact on ecosystem forestry. The standards are very regional, so general messages about which tree species to plant across Europe are not possible. However, how the European forest will react [ao desafio] It’s in our hands. What we plant today will shape the forests of the future, and this decision is one of the most pressing right now”, explains to PÚBLICO Johannes Wessely, first author of the study Nature Ecology & Evolution.

When it comes to Portugal, the authors do not provide disaggregated data. “I know you would like to have more specific results for Portugal, but that is quite complicated. What we see in Portugal are many changes. Many of the tree species that are suitable in a region today will not survive in those regions until the end of the century. On the other hand, during the century, different species will become suitable for planting in these locations”, comments Johannes Wessely, in a response by email.

Handpick species

Hand-picking the species we are going to plant is important above all because European forests are already losing too many trees – whether because of hydrological drought, whether due to beetles. “In Europe, for example, tree mortality has increased sharply over the past three decades, and recent waves of tree species mortality were probably unprecedented in the past 170 years,” the article reads.

These changes in the European landscape have brought enormous challenges to forestry policy and management. This is because it is not enough to plant trees to replace those that have died; it is necessary to choose resilient species. As trees have a long life cycle, the species we are choosing to reforest Europe must be adapted not only to the current climate – in which there is frost, for example – but also to that of a warmer future and dry.

The study considers three distinct climate scenarios: one optimistic, one moderate and one pessimistic. These scenarios result from calculations about what the climate could be like in the future due to the growth in concentrations of gases with greenhouse effect. They were prepared by the Intergovernmental Panel on Climate Change (IPCCthe acronym in English) of the United Nations so that the scientific community can work with precise and comparable references.

Wood, carbon and habitat

Forests are a powerful tool in climate action, but at the same time, they themselves are threatened by rising global average temperatures. More intense and frequent extreme climate phenomena – such as hydrological drought or heat waves, which in turn favor forest fires – make it unrealistic to expect these ecosystems to continue to function ecologically in the same way. Climate pressure will therefore threaten the very “services” that the forest provides to society, such as carbon sequestration and the provision of timber or habitats.

In the study, species were also assessed for their potential to provide timber, store carbon and provide habitats in current and projected climate scenarios. Scientists found that the average number of tree species per square kilometer capable of surviving throughout the 21st century could decrease by around 33% and 49% in the most optimistic and most pessimistic scenarios, respectively.

In other words, there will be even fewer species available for the forestry industry in the coming decades. Depending on geography, between a third and half of the tree species that exist today will not survive.

“Our work clearly shows how seriously the vitality of forests is affected by climate change. We cannot rely solely on a new mix of tree species; Rapid measures to mitigate climate change are essential for the sustainable protection of our forests”, says the study’s first author, Johannes Wessely, in a press release from the University of Vienna, Austria.

Where is the diversity?

Furthermore, in the moderate climate scenario, only an average of three species with the potential to provide timber, habitat and carbon storage remain suitable per square kilometer, highlights a note from Nature. This creates a certain “bottleneck” of species possibilities or, in other words, choices are profoundly limited by climate.

“What is rarely considered, however, is that climate change could create considerable species strangulation for today’s forest management: species that are climatically suitable in a given region today may no longer be suitable in a future climate”, reads the article.

This bottleneck means that, in practice, forest managers will have few options if they want to choose species compatible with the current and future climate. This means, in practice, recreating spaces with less diversity – which is not usually healthy for an ecosystem.

“Mixed forests made up of many tree species are an important measure to make forests more robust against disturbances like beetles. However, in some places in Europe, we may run out of tree species to establish such colorful mixed forests”, explains co-author Rupert Seidl, researcher at the Technical University of Munich, cited in the same document.