The Forest of the Future

Forests across Germany are dying off on a massive scale. Many native tree species are not sufficiently adapted to the changes brought about by climate change, such as prolonged droughts and insect damage. This year’s debate focused on whether forest restructuring is necessary – that is, whether new provenances of native tree species or even non-native species could help secure the future of forests, or whether the forest might recover on its own.

Mapping Temporal Changes in Space

Dr. Christian Kölling, former head of the Soil and Climate Department at the Bavarian State Institute of Forestry, opened his talk by emphasising the urgency of the issue. “We are in the midst of a forest crisis,” said the forestry scientist, who has been researching forests and climate change for over two decades. He pointed out that, for instance, the Scots pine thrived in Middle Franconia for 650 years, becoming the dominant tree species of the region, but is now under threat from widespread dieback caused by increasingly extreme heat and drought. Similarly, spruce in Upper Franconia faces a comparable fate.

Kölling argued that climate changes are largely predictable, and both temporal and spatial dimensions are key to understanding them. By examining “twin regions” – areas where the current climate matches the expected conditions of a given region in the coming decades – it is possible to identify tree species suitable for future climatic conditions. “If the climate moves, the forest cannot stand still,” Kölling stated, advocating for the concept of assisted migration, which involves supporting the relocation of non-native tree species to climatically suitable areas to make forests more resilient and maintain their ecological functions.

Seed Sources Matter

Integrating Exotic Tree Species

The implications of forest restructuring go beyond forestry to affect entire forest ecosystems, as illustrated by Professor Elisabeth Obermaier (Ecological-Botanical Garden, University of Bayreuth) and Professor Johanna Pausch (Professorship Agroecology, University of Bayreuth).

In her presentation, Professor Obermaier highlighted the critical role of insects, which not only represent a significant portion of global biodiversity but also perform essential ecosystem functions as pollinators and food sources. Findings from her “Common Garden Experiment” – which investigated numerous species across four genera of trees and compared them with a native reference species – revealed that insect diversity decreases as the evolutionary distance between exotic and native tree species increases. To preserve biodiversity, evolutionary relatedness should take precedence over geographical proximity when selecting non-native tree species.

Professor Pausch demonstrated how interactions between trees and fungi influence the carbon cycle in forest soils. Mycorrhiza – the symbiotic relationship between fungi and plants – is the oldest known symbiosis on Earth. The fungal networks in soil store vast amounts of carbon, and the two types of mycorrhiza – ectomycorrhiza and arbuscular mycorrhiza – differ in their functionality, their impact on soil carbon, and the tree species they associate with. Therefore, mycorrhizal symbiosis must be considered when selecting tree species.

Non-Native Tree Species: Hope or Risk?

Continuing the overarching theme, Professor Andreas Bolte (Director of the Thünen Institute of Forest Ecosystems in Eberswalde) illustrated the debate on non-native species through a current controversy: the selection of the northern red oak as the Tree of the Year 2025. While it is a neophyte – a species introduced outside its native range after the late 15th century – its invasiveness is a contentious issue. Factors such as dispersal biology and management options must be considered when discussing neophytes. Given that the mortality rate of native species like spruce is at a record high, and their climate mitigation potential is diminishing due to climate change, Bolte argued that the inclusion of “immigrant” tree species through assisted migration is essential to fill this gap.

Jana Ballenthien, a forest policy officer for Robin Wood – a grassroots environmental organisation – concluded the lecture series with a talk titled “Let Nature Be Nature.” Shifting the focus away from tree species, she emphasised aspects that should also be considered in the forest transformation debate, such as embracing deadwood, old-growth forests, and native species, as well as promoting sustainable ecological forestry. She called for financial support for forest owners to achieve these goals.

During the subsequent Q&A session, the need for stronger communication between forest owners and conservationists was highlighted. The final panel discussion found a broad consensus: while a divide exists between forest owners and conservationists, neither party is responsible for the current state of forests. Instead, society must be made aware of the vital role forests play in human survival, and the challenges posed by climate change must be brought to public attention. However, a clear plan is needed to shape the forest of the future.

A Path to the Forest of the Future

On the second day of the Forest Controversies Forum, participants took part in an excursion in the Bayreuth area. At the Schmellenhof trial site of the Bavarian State Institute of Forestry near Schnabelwaid, where tree species are being tested for their suitability under current and future climatic conditions, the discussions were particularly contentious. Although such trial sites provide valuable insights, results often come too late, whereas twin regions can already provide clues about future climatic conditions. This was followed by a visit to the Bindlach nursery of the Bavarian State Forests, where questions about the availability and propagation of plants were explored. The final stop was a research site belonging to the student-led Climate Forest Project, supported by Bayreuth’s municipal forestry office and the Forum Future Forest association. Here, participants examined the potential of natural regeneration as well as the opportunities and risks associated with native and alternative tree species. The consensus was that while natural regeneration should be allowed, expectations must be tempered due to climate change.

At the close of the intensive Forest Controversies Forum, one thing was clear: climate change poses a serious threat to the future of forests. While introducing new provenances of native or even non-native tree species offers a potential solution, the risks associated with introducing foreign species to ecosystems must not be overlooked. Above all, it is vital to raise awareness of the importance of forests for society and to communicate the challenges facing forests in the context of climate change to the broader public.