Whispering willows, talking trees and forests rich with conversation – these seem like fantasies taken from the writings of Tolkien, C.S. Lewis, or children’s fairytales. However, what was once considered the realm of imagination is now grounded in scientific research. Beneath the canopy, trees engage in a fascinating dialogue, creating a complex network of relationships, alliances and rivalries that competes with the most riveting of human dramas.
Darwin’s ‘survival of the fittest’ paradigm, often accepted as an established model of how trees compete, is challenged by emerging findings. Contrary to the notion of ruthless competition, a growing body of scientific evidence suggests that trees of the same species exhibit communal behaviour and can even forge alliances with trees of other species. Forest trees have adapted to flourish in communities, exhibiting a hive-mind-like intelligence facilitated by an often-overlooked natural system: fungi.
Mycorrhizal networks
Specialised fungi establish connections with the root systems of multiple trees via their hyphae (branching elements common in fungi), forming a ‘mycorrhizal network’. This underground alliance allows for the exchange of essential nutrients, such as phosphorus and nitrogen, whilst giving fungi greater access to carbon. This fosters a symbiotic relationship that enhances the resilience and vitality of the forest ecosystem. Through these internet-like connections, trees can share resources, warn each other of potential threats such as pests or diseases, and transfer information about environmental changes. Wise old mother trees have been shown to share resources with their sapling progeny, nourishing them with liquid sugar whilst warning neighbouring trees of impending threats.
Recent research from the University of Lisbon and the Chinese Academy of Sciences has shown that around 80% of terrestrial plant species form mycorrhizal associations. While some mycorrhizal fungi may exhibit host-specific tendencies (e.g. Rhizophagus irregulars), most function as generalists, colonising a wide range of species. This versatility allows for the exchange of information and resources even between different plant species.
Volatile communication
While this subterranean network unfolds, further dialogue plays out above ground. Plants release BVOCs (biogenic volatile organic compounds) such as isoprenoids, green-leaf volatiles and aromatic compounds from various organs including their leaves, flowers, and roots. These emissions are regulated by plant hormones, which respond to environmental factors. Within minutes of insect feeding starting, volatile compounds are released and can be continuously emitted until several hours after damage initiation, alerting nearby plants to the danger. This behaviour has been observed in many species. For example, in caterpillar-infested willows, it has been suggested that, upon attack, the release of plant ‘pheromones’ induces resistance to herbivory (being eaten) in their neighbours. Similarly, scientists from the University of Eastern Finland have observed birch trees releasing an ‘un-birch-tree-like’ compound upon herbivory by aphids, dissuading the green insects from ravaging nearby trees.
Caring for our green planet
Interspecies communication is increasingly recognised as a vital element in maintaining the overall health of forests and natural ecosystems, with birch leaves even being shown to adsorb and re-release insect-repelling compounds produced by rhododendrons. This fascinating interplay highlights the interconnected nature of our forests and the importance of ecological diversity.
With 31% of the planet’s land area being forested, 30% of which is managed for timber production, humans have a responsibility to ensure the health of global forest populations. Extensive logging practices have led to a growing prevalence of monoculture forests, disrupting the balance of historic woodlands. Now more than ever, it is imperative for logging industries to prioritise the safeguarding of intricate forest networks by maintaining ancient mother trees and promoting species diversity. Such measures would not only benefit the forests but also improve the sustainability of the timber industry – all while preserving the beauty of our ancient forests for generations to come.
Image credit: *AMS* on Flickr.