Adaptive forestry: Last minute for action
What will happen with our forests if temperatures increase by 2 degrees - the UN target for average global temperature increase? And what will happen if the world leaders do not manage to make an agreement ensuring this target – and the temperature will increase even more? Professionals speaking on Forest Day 3 made it clear that even an average temperature increase of 2 degrees will have major impacts on our forest ecosystems.
If we go above that, the most commonly used word was "catastrophic".
Genetic diversity of trees is crucial
The genetic composition of the tree species growing naturally in a forest has become adjusted to the current climate based on thousands of years of natural selection. Abrupt changes in climate imply that those genes are no longer optimal for the new conditions.
You might think that many common species such as spruce, pine, oak, beech etc can grow under very different climatic conditions and that they will therefore easily adjust to changes in climate. However, Professor Erik Dahl Kjær from the Forest & Landscape Department, University of Copenhagen, demonstrated that even if a species has a large natural geographic range, seeds sourced from one area may not be viable if planted in a different area. The climatic adaptation of the local gene pool is often crucial. As temperatures increase, it can thus be expected that plants growing in a certain place will no longer be adapted for the conditions there.
Forestry is not agriculture
A crucial difference between agriculture and forestry was also highlighted by some speakers. Farmers can switch to different crops which are better adjusted to the new climatic conditions. If the climate is no longer good for barley, then you can switch to corn the next year.
This is not the case in forestry. A tree planted today is not expected to be harvested within the next 100 or 200 years. An individual tree may be well adjusted to the current climate conditions, but as it matures climate will change and by the time the tree reaches harvesting age it may be growing in a completely different climate. That is, if it ever reaches rotation age.
Infrastructural barriers to natural gene flow
The Earth has experienced significant climate changes in the past, so you might think that species can adapt the way they have obviously done before. But current climate changes are happening over an extremely short period of time; the planet has not experienced such rapid climate change for thousands of years.
Furthermore, under natural conditions the global forest cover would be more expansive, and tree species with their genetic makeup would be able to move through the forest ecosystems in response to climate changes much more easily. But due to human impact, a significant part of the forest ecosystems has been replaced by agricultural land or infrastructure. The mobility of species and genes is therefore greatly reduced compared to the conditions prevailing in the natural ecosystem.
Expert advice: establish gene pockets
For years, using local genetic material in forestry to ensure adaptation to local conditions has been considered good forest management practice. This approach does not seem valid in the current situation.
Since we don’t know exactly how our climate will be in 100 years, it is difficult or impossible to give clear guidance on what to do. Speakers at Forest Day 3 provided the following advice:
- Promote mixed stands based on the philosophy that if one species fails, then another may survive and you still have a forest.
- Increase the use of species with low harvesting ages. If trees can be harvested after e.g. 50 years instead of 100 years, then the expected range of climate change during their life time will be smaller and the chances that they will survive until maturity are higher.
- Introduce new genes by using seeds from areas that are likely to match a future climate. This can be done by planting/sowing in smaller patches. Genes from these 'genetic pockets' can later spread if they are more successful under new conditions.
More extreme weather conditions
On top of the challenges surrounding genetic adaption, we can expect more extreme weather conditions such as storms, drought, and flooding. Extreme weather conditions that used to occur only once in a 100 years are now more like to happen every 10 years, and it is predicted that such events will become even more common in the future.
Our forests - already under pressure due to climate change - will thus come under further stress due to extreme weather conditions. This further underlines the importance of selecting the right species and adapting the forest management to future weather conditions.
Need to reconsider certification rules
These issues naturally lead to the important question – are the certification requirements of forest management certification systems such as FSC appropriate, taking into account our current knowledge about the likely effects of climate change?
It appears that there is a clear need for adjustment. Although the FSC rules do already promote forest health and resilience in several aspects, the standards also focus on the use of local genes and protection of natural ecosystems. It might be fatal if forest managers do not start to consider how to adapt silvicultural principles to the future climatic conditions. Adjustment of the certification rules to require adaptive forestry is a matter of urgency.
As former Norwegian Prime Minister and 'mother' of the Brundtland Report Gro Harlem Brundtland expressed it in her keynote speech on Forest Day 3: "Forests are under threat and time is of essence".
