Inaugural address Frank Sterck: Towards the future with climate smart forests

Today’s forest does not differ fundamentally from a forest three decades ago. The physical and societal environment, however, has altered. The demand for products from forests, such as timber and biomass, has increased, while the demand for forests as a place for leisure has also increased. At the same time, space is limited, especially in a country such as the Netherlands. This means that forests compete with other types of land use. Trees face an additional challenge in depleted and acidified soil, which has been going on for decades and continues to impact the soil.

Extreme drought

One of the biggest challenges forests face is the increase in extreme droughts and heatwaves, which has increased tree mortality rates worldwide, according to Sterck. The forests of today and tomorrow must be able to cushion the effects of climate change. The extreme drought in the spring of 2018 showed that certain tree species, such as the Norway spruce, have a much higher mortality risk than others. This species suffered the most significant impact as it had difficulty adapting.

Sterck’s research shows that species such as the Norway spruce have a higher risk of perishing in drought or heat than other conifers. ‘The needles probably get damaged and are not replaced sufficiently fast. This weakens the spruce, making them more susceptible to fungi and insects.’ Thus, ultimately, perishing.

Resilience

Species with the capacity to replace their leaves or needles quickly have a distinct advantage, Sterck discovered. Moreover, trees that shed their leaves during a drought contribute less to evaporation and desiccation. These species retain their strength for the next year. ‘Strategies such as these make some species more resilient than others, especially with the increasing incidents of extreme weather as a result of climate change’, Sterck stresses.

No two trees are the same

There are also differences in resilience between trees of the same species, Sterck’s recent research shows. Growth ring analyses revealed what trees were more or less doomed decades ago to perish during recent bouts of severe drought. He maps other differences between individual trees using sensors attached to the trunk, 3D imaging of the treetops and mathematical models. The combination of all this data is the key to climate-smart forests, Sterck believes. This new form of management takes climate change into account.

Sustainable management

Politicians increasingly acknowledge the need for climate-smart forests. Sterck: ‘Not only does the climate impact forests, but the forests also impact the climate. Forests contribute to rainfall and have the ability to sequester carbon.’ With this in mind, agreements were established in the 2015 Paris Climate Accord and the European Green Deal (as of 2020).

These agreements provide a considerable push for sustainable forest management, Sterck underscores. He sees increased support among forest managers. ‘Almost everyone is convinced, but we are still trying to find the optimal way to design the forest.’

Intermittent logging

Currently, it is common practice to cut down an entire plot in one go. Following that, the forest can re-grow. ‘It is likely better to avoid cutting down a complete plot but rather harvest small amounts of timber intermittently. This enables saplings to grow, leading to a layered forest, more diverse in structure and species’, Sterck explains. ‘This is not a novel idea, but it has never been properly tested.’ He intends to study what species are best combined, what trees can be felled when and how this should be included in forest management.

Predictions

Based on the extensive data on trees and their environment, both from the present and the past, Sterck wants to be able to more accurately predict their future. Managers can benefit. ‘A forest is not just relevant because of the products we obtain from them, but also to conserve nature and biodiversity. Finding the best management strategies is a delicate matter. Forests play many different roles in society, and the question is how to include all these roles. I try to contribute from a scientific perspective.’