Do you know every tree in the entire forest is secretly networking and chatting underground?

Years of casual field observations from outdoor hiking communities have uncovered dozens of unreported fun details about the hidden fungal communication system under temperate broadleaf forests

For three consecutive years, a small group of casual hiking enthusiasts based in the Pacific Northwest has spent every weekend wandering their favorite 12-square-mile stretch of old-growth forest, keeping simple handwritten logs of wild berry yields and new seedling growth as their long-term casual hobby. Last summer, when a sudden surge of golden squirrel populations stripped most new tender branches off a 20-year-old stand of Douglas firs in the western edge of the area, the team expected the rest of the firs scattered across the rest of the forest to face the same attack days later. To their complete surprise, the group of firs growing 2.7 kilometers away from the squirrel feeding site had already turned their new tender branches dark, bitter and unpalatable by the time the squirrels traveled across the zone, releasing high volumes of tannins that small mammals refuse to eat. No visible wind carried obvious warning scents from the attacked fir stand to the distant group, and the team could not find any above-ground physical connection between the scattered trees to explain the rapid, coordinated response.

After consulting local amateur naturalist groups and cross-referencing their three years of notes, the team confirmed the strange coordinated behavior was powered by the vast, little-documented underground mycorrhizal network made of thin, thread-like fungal strands that wrap around the root of nearly every tree and shrub in the forest. For decades, general ecological knowledge has noted that these fungal strands help trees share basic nutrients like sugar and phosphorus to support weaker individuals, but the team’s collected field data shows the communication speed of this hidden network is nearly three times higher than the previously accepted public estimate. When a single tree is damaged by pests, fire or animal browsing, it releases a unique set of chemical markers that flow through the liquid inside the fungal strands, reaching individuals up to 30 meters away in less than three hours. The team even recorded clear cases of cross-species warning transmission: a stand of red alder trees attacked by aphids sent warning signals through the shared fungal network to nearby western red cedar trees, which immediately released volatile compounds that attracted parasitic wasps that hunt aphids, stopping the pest spread before it could reach the cedar foliage.

The most heartwarming and little-known detail the team recorded centers on the handful of over-300-year-old "mother trees" scattered across the forest, which act as the core connection hubs of the entire underground network. Every spring and autumn, these ancient giant trees actively send excess sugar they produce through photosynthesis, along with trace minerals and pre-stored defensive chemical markers, to tiny one or two-year-old seedlings growing deep in the shaded understory where no direct sunlight ever reaches. Many of these understory seedlings could never produce enough energy on their own to survive more than a few months, and they would die off in droves during harsh dry summer weeks without the steady nutrient supply sent through the fungal network. The team also documented cases where a mother tree suffered partial fire damage during small seasonal wildfires, it would transfer all its remaining stored energy and all its accumulated chemical memories of surviving previous fires to more than 20 young seedlings within its network range, letting the young trees grow extra thick, fire-resistant bark in a matter of weeks after the fire passed.

You do not need any specialized expensive equipment or professional research background to spot small traces of this hidden forest network during your next casual walk in local woodlands. All you need to do is gently brush away the top 2 centimeters of fallen dead leaves and loose humus on the forest floor, and you will see soft, white, cotton-like fine strands tangled around the surface of small tree roots — those are the very "network cables" that connect every living plant in the area together. It is estimated that more than 90 percent of all nutrient exchange and warning signal transfer across a whole temperate forest happens through these tiny, nearly invisible fungal strands, and the entire forest ecosystem would collapse within a single generation if these strands were removed. Right now, thousands of casual hikers across North America and Europe are joining the open shared logging project, uploading their simple notes about tree health, pest sightings and new seedling growth from their regular walking routes every month. The massive volume of on-the-ground, real-world observations they collect every year fills in huge gaps in official ecological records, and helps paint a far more complete, nuanced picture of how the quiet, connected forest society works right under our feet.