By: Varvara Vasylchenko

Trees possess the extraordinary ability to tackle multiple environmental problems at once. Known as Earth’s oxygen generators, they absorb carbon dioxide, improve air quality, cool the environment, prevent soil erosion and provide habitat for countless species – from birds and squirrels to insects and microorganisms. Yet trees in modern, human-managed forests often appear to be less resilient than those in ancient, untouched woodlands. So what secret do natural forests hold? 

For a long time, trees were seen as solitary beings competing for water, sunlight and nutrients. However, recent research has completely overturned this view. It was revealed that trees are not isolated at all; instead, they form an underground network, helping each other to survive. Their communication is made possible by a remarkable symbiosis with another species – fungi. The thread-like vegetative body of fungi, known as mycelium, acts like a cable, linking trees by weaving around and through their roots. This “wood wide web” allows trees to share resources, warn each other about pests and balance nutrient distribution. In essence, it functions like a “social support” system that ensures no struggling members of the tree community are left behind. 

Remarkably, despite differences in age, access to sunlight, amount of water and composition of soil, trees in ancient forests photosynthesise at nearly the same rate. This would be impossible in a purely competitive environment because weak and sick trees would never match the performance of strong plants. In the natural environment, cooperation overrides competition. In contrast, commercially exploited forests show large differences in performance. Clearings create physical gaps that disconnect the root systems, making it harder for trees to exchange nutrients. Therefore, the redistribution is less evident because trees cannot reach each other.

Research by María A. Crepy and Jorge J. Casal has shown that trees can even behave altruistically in favour of their family members. When an Arabidopsis plant is located close to its genetic relative, it adjusts its leaf position to allow its neighbour more sunlight. This kind of considerate behaviour is particularly evident in ancient forests, where generations of related trees have been living side-by-side for centuries. By giving space to each other, trees maximize the total leaf area exposed to sunlight, benefiting all members of the tree community. As a result, trees growing among their kin produce more seeds and biomass. 

Even more astonishingly, trees can recognise and nurture their own offspring. Through underground root networks, “mother” trees identify their seedlings and send them water, nutrients and sugar solutions. This support is vital for young trees, whose roots are too short to access deeper groundwaters, making them more vulnerable to droughts. In a packed forest, most water from the rainfall also never reaches the ground, becoming trapped in a dense leaf canopy. As a result, small trees would barely satisfy their thirst with scarce summer droplets. Without parental care, most saplings would not survive harsh weather conditions. 

Unfortunately, the modern forestry industry rarely considers these natural bonds while planting trees. Some saplings are lucky enough to have a large tree nearby, but those growing with no trees around become unprotected “orphans,” left vulnerable to storms, devastating droughts and hungry herbivores. Greater “social” distance also limits their access to the underground network, reducing their chances of receiving support from neighbouring trees. 

Forests composed entirely of young trees are also less efficient at saving water for the future. Shallow saplings’ roots cannot physically uptake as much water as mature trees would, so most of the liquid seeps underground. The absence of older trees weakens one of the tree community’s climate-regulating functions: cooling the temperature. Mature trees store huge amounts of water, evaporating it during the hot season and acting like forest’s natural air conditioners. Small trees cannot absorb the same volume, so newly planted young forests do not regulate the temperature as efficiently as intact woodlands do. 

Nonetheless, it should be admitted that growing in dense forests comes at a price. Large trees create a shade, which prevents most of the sunlight from reaching the sapling. Parental supply of sugar solutions does not fully compensate for the lack of sunlight, which makes young trees grow extremely slowly, often remaining under the mother’s shade for decades or even centuries.

In forestry, restrained growth is generally seen as a problem. In order to accelerate it, the industry came up with thinning – a practice of removing “competing” trees so that the remaining ones receive more sunlight. Appreciating the opportunity, survivors grow faster and taller, reaching maturity within several decades. However, speedy development comes with its hidden costs. A slow growing pace in the shade allows trees to develop strong wood, making them more resistant to storms. Their solid trunks leave little room for fungi to invade, so they are also less susceptible to disease. In contrast, trees that expand rapidly have lighter and more porous wood. They are structurally weaker, break more easily, and live shorter lives. Reaching maturity sooner, they exhaust their resources quicker and die sooner as well. Their shorter lifespans undermine one of the forest’s crucial functions: long-term carbon storage. Trees expand in diameter with every passing year, taking up more carbon as they become older. Beeches and oaks, for instance, sequester carbon dioxide at the same rate for 450 years before slowing down for a little. In fact, one large tree stores more carbon than a lot of small saplings taking up the same space. Unfortunately, fast-growing trees rarely reach old age, which significantly limits the amount of carbon they can store.

Sometimes poor nursery practice can also harm the most delicate and intelligent part of a tree – its roots. Roots do not just transport resources and store water – they are sensory organs used for detecting dozens of parameters, including temperature, moisture, soil chemistry, gravity and the presence of other plants and bacteria. Based on this input, trees alter their water intake, cooperation with other organisms and growth direction. In the wild, a 40-centimeter beech extends its roots to 1 square meter, striving to access as many locations as possible. This makes replanting a tree that has a developed root system nearly impossible without causing damage. This would imply transporting a block of soil as well, so nursery trees are often trimmed before planting. 

While pruning does stimulate root growth, serious harm prevents future roots from growing as deep and wide as they could have. This leads to reduced water and nutrient absorption, slowing down the growth rate. Damaged roots also produce less root exudates (sugars used for interaction with soil microorganisms), which disrupts communication and symbiosis with other species. Such trees with less developed root systems are poorly attached to the ground, which affects their stability and increases the likelihood of being blown down by strong winds. Therefore, storms might have a more devastating impact on modern forests than untouched ecosystems.

All in all, forests are not mere collections of trees – they are living communities that need cooperation to thrive. Ancient woodlands remind us that true power lies not in the vicious cycle of competition but in reciprocal relationships. If we hope to restore self-sustaining and climate-resistant forests, we must look beneath the surface and acknowledge their invisible networks.

Some insights are from ‘The Hidden Life of Trees” by Peter Wohlleben