It might be quite a surprise to discover that, like many animals, Trees also communicate with each other and are able to pass on a legacy to new generations. A fascinating underground network connects trees, allowing for a collaboration between them that is much more complex than previously thought. This phenomenon has been demonstrated by Professor Suzanne Simard of the University of British Columbia, through her work that challenges traditional assumptions of Darwinian competition between organisms. Although Charles Darwin assumed that Trees are organisms While individual trees compete for survival, trying to reach for more height and light, Simard has shown the opposite. According to his research, trees survive best when they cooperate and support each other, sharing essential nutrients through an underground network of fungi known as mycorrhizae.
The role of mycorrhizae in communication between trees
Mycorrhizae are a network of fungi that symbiotically associate with tree roots. Through this connection, the fungi absorb carbohydrates from trees, while in turn providing essential nutrients such as nitrogen, phosphorus, and water. This interdependence is key to forest health, as the Nitrogen and carbon are shared by this network, ensuring that all trees in the ecosystem receive the resources they need to stay healthy. The mycorrhizal network can be compared to a gigantic underground 'internet', often called the Wood Wide Web, which connects individual trees to each other and facilitates the exchange of information and resources. This network is so vast and effective that it has been observed that the largest and oldest trees, known as 'mother trees', act as nerve centers of this network, distributing nutrients to smaller, younger trees that need help to grow.
Mother trees and their crucial role in the ecosystem
Simard has extensively studied the role of mother trees. These trees, which typically have deeper roots and a greater number of connections to the mycorrhizal network, are the life support of the entire forest. These connections allow mother trees to share important resources, such as carbon, with young seedlings that are not yet able to capture enough light or nutrients on their own. An experiment conducted by Simard in British Columbia revealed how these mother trees transfer isotope-labeled carbon to the seedlings around them, promoting their growth and survival. Surprisingly, seedlings isolated from the mycorrhizal network did not receive these nutrients and showed a much lower survival rate. Before dying, mother trees also accelerate this process of transfer of resources, ensuring that the next generation has a solid foundation to grow on. This process underlines the interdependence of trees within the forest ecosystem and how they act more like a cooperative community than isolated competitors.
The exchange of warning signals between trees
In addition to sharing nutrients, trees also use the mycorrhizal network to send each other warning signs in case of danger. When a tree is attacked by insects or pathogens, it can alert its neighbours through these underground connections. This chemical dialogue allows nearby trees to activate their defences, such as the production of resins and toxic compounds, before they are attacked. For example, in a controlled experiment, some Oregon pines were infected with insect larvae, and the trees connected by mycorrhizae responded by activating their immune systems. Interestingly, the pines that had been isolated from the mycorrhizal network did not show any defensive response and were more vulnerable to attack. This phenomenon shows that trees do not only act individually, but cooperate to protect the entire ecosystem, alerting each other to possible imminent dangers.
Air communication: volatile compounds
Although the underground mycorrhizal network plays a crucial role in communication between trees, trees also communicate through the air using volatile organic compounds (VOCs)These chemical compounds, such as ethylene, are released by the leaves and roots of trees when they are under stress or attacked by herbivores. A classic example is that of African acacias, which generate ethylene when they are nibbled on by herbivores such as giraffes. This compound, in turn, is detected by other nearby trees, which respond by increasing the production of tannins, compounds that make their leaves less palatable and even toxic to herbivores. This chain reaction allows nearby trees to prepare for the same danger before it arrives. This type of volatile communication also plays an important role in attracting pollinators and natural predators that feed on the insects that are attacking the trees. In this way, trees can use other species as part of their defense strategy, making the ecosystem even more interconnected.
The impact of climate change on forests and their communication network
Climate change is drastically affecting forest ecosystems and, therefore, the communication networks between trees. Rising temperatures, reduced rainfall and more frequent forest fires are altering the composition of forests and their capacity to regenerate. A study carried out in the Iberian Peninsula revealed that Tree species are migrating to higher, colder areas to adapt to new climatic conditions. For example, beech forests are moving to higher altitudes, while oaks are being replaced by more drought-resistant species, such as kermes oaks. Climate change is also affecting the regeneration cycle of trees. Flowering has come forward by up to 20 days in some areas, which has desynchronised the relationship between trees and pollinating insects. This lag could have serious consequences for forest biodiversity in the future.
The crucial role of forests in mitigating climate change
Forests are not only victims of climate change, but also a crucial solution to mitigate its effects. Trees act as a carbon sink, absorbing vast amounts of CO2 from the atmosphere during photosynthesis. Trees globally are estimated to contain around 7.600 billion metric tons of carbon, equivalent to about 1,5 times the annual emissions of the United States. But for forests to continue to play this vital role, it is essential to protect them from deforestation and promote their regeneration. Deforestation, in particular, is progressing at an alarming rate in regions such as the Amazon, which is putting the planet’s ability to absorb CO2 and regulate the global climate at risk. Forests are also essential to maintaining biodiversity, as they are home to approximately 80% of the planet’s terrestrial species. The loss of forests not only contributes to climate change, but also threatens the survival of thousands of animal and plant species. In short, trees are not solitary organisms.They interact, cooperate and help each other through an underground network of mycorrhizae and through chemical signals in the air. This interconnection allows them to share nutrients, warn each other of imminent dangers and collaborate in the defence of the forest. However, the threats of climate change and deforestation are endangering these ecosystems, so it is vital to recognise their crucial role and work towards their preservation.