Climate Change Moves Trees Away From Habitats, Leaving Behind Their Fungal Partners

As trees seek refuge from the effects of climate change, their fungal partners are being left behind. Ectomycorrhizal fungi, which form mutualistic relationships with the roots of trees, are essential for nutrient and water uptake. Yet, if trees move to new habitats in search of more favorable conditions, they’ll find themselves without the supportive network of fungi that has helped them survive for millions of years. According to a recent study, climate change could negatively affect many tree-fungi relationships, especially North American pines. Now, scientists are concerned that forest biodiversity and stability could be at risk as these symbiotic relationships deteriorate.

The importance of fungi-tree relationships

Fungi can greatly support tree growth by enhancing their nutrient and water uptake. They colonize tree root systems, extending their reach underground, which helps their host obtain essential nutrients like nitrogen and phosphorus. In return, the tree provides the fungi with carbohydrates made from photosynthesis. 

Trees greatly benefit from this partnership, especially in nutrient-poor soil or during times of drought or disease. The extensive fungal network significantly expands the root system of trees, allowing them to access resources that would otherwise be out of reach. However, if this relationship is disrupted, trees may struggle to adapt to new environments, threatening the overall health of forest ecosystems.

Climate change and tree migration

Because of rising global temperatures, many species, including trees, have been migrating away from their historical habitats into cooler regions in order to survive. However, these new areas often lack the fungi necessary to support tree health. Ectomycorrhizal fungi react differently to climate than trees do, so they remain in place while the trees shift away. 

Scientists have noticed that this lack of fungi is causing a significant lag in the migration process since trees are struggling to establish themselves without their fungal partners. This lag not only affects the survival and growth rates of individual trees but also has consequences for forests as a whole. Although we are not seeing the consequences of this conflict yet, the potential impacts are alarming. 

The study, published in PNAS, revealed that approximately 35% of symbiotic relationships between trees and ectomycorrhizal fungi are negatively impacted by climate change. This figure, derived from extensive modeling and analysis of the distributions of trees and fungi, took into account various climate scenarios and their impacts on these relationships. North American pines, in particular, were found to be especially vulnerable, as they heavily rely on these fungi for their survival (1).

If this pattern continues, the natural composition and diversity of forests could shift, and trees may see higher mortality rates or reduced growth, which could further compromise forest health. 

Addressing the conflict

The researchers of the study emphasize the importance of using advanced data science to map out hidden fungal networks. By doing so, they can understand where ectomycorrhizal fungi are located and how they interact with trees so that conservation efforts can be better focused on the areas most at risk. Monitoring these relationships over time will also provide more information about the long-term impacts of climate change and how effective different intervention strategies are.

“It’s absolutely vital that we continue to work to understand how climate change is affecting mycorrhizal symbioses,” said Michael Van Nuland, lead author of the study and fungal ecologist at the Society for the Protection of Underground Networks (SPUN). “These relationships underpin all life on Earth – it’s critical that we understand and protect them.”