earth is home to around 1 billion trees that belong to over 60 thousand species and they live on every continent but antarctica and while they may seem extremely vulnerable to environmental changes seeing as they can’t get up and leave when the climate no longer suits them trees have actually been around for close to 400 million years they’ve survived all four extinction events that they’ve been around for and their ability to break down rocks create soil and siphon carbon dioxide from the air and replace it with oxygen is what made our planet habitable for humans but however grateful foresters poets and lumberjacks might be for their presence trees have always been a bit difficult to understand when it comes to finding similarities between trees and animals there’s not a lot to work with trees are immobile don’t have blood or lymph or nervous systems and only need sunlight and water to produce their own supply of food they can live for thousands of years growing slowly taller and wider one great base in bristlecone pine is over 5 000 years old and even in a forest they seem like solitary individuals competing for access to sunlight but otherwise having no interactions with their neighbors but as it turns out there’s more to trees than meets the eye it was only a matter of looking deeper down to the roots instead of up to the canopy while we might only see and hear the birds and squirrels filling forests with noise there’s a vast network of communication happening right under our feet trees sharing resources passing on warnings and passing down information over the generations a network of trees talking it allows the forest to behave as if it’s a single organism and makes scientists rethink the evolution of tree life is it based on competition or cooperation and by understanding this network we might be able to unlock secrets that will help in our fight against deforestation and climate change as a whole on our planet mutualism is a fundamental part of many organisms biology the clownfish that gets protection from an anemone the anemone that gets nutrients from the fish the cleaner ras who eats parasites from reef fish the reef fish staying healthy the bees that gather nectar from flowers while the pollen stuck to their bodies pollinates it but perhaps the most widespread and ecologically significant symbiosis is one we can’t see a partnership between soil fungi and land plants in 1885 german botanist albert bernard frank first proposed the idea that plant roots and the fungi around them were working together and like with many bold scientific assertions he was basically laughed out of the room but in the last century nearly all of frank’s major hypotheses have been unequivocally demonstrated we now know that plant and fungal associations known as mycorrhizal associations are present in almost all ecosystems from deserts to tropical forests and that about 90 percent of terrestrial plants are connected to some form of mycorrhizal fungi network mycorrhizae are a fungus which grows in association with the roots of a plant in a symbiotic relationship the most common fungal networks are made of arbuscular mycorrhiza which are named for the latin arbiscule meaning little tree the threads of this fungi penetrate the root cells of their host and form tiny structures inside of them this is how they interact with the trees and share resources with them the other major class of fungi are ectomycorrhizal fungi these fungi form a sheath around the roots of their hosts and grow between the plant cells to exchange nutrients they have a symbiotic relationship with fewer plants than the arbuscular mycorrhizae but their hosts tend to be the most economically important trees as they are often the most widespread trees that we use for timber while the two classes of fungal networks belong to very different species their relationship with the host plants are pretty similar the fungi pick up water and nutrients from the soil including phosphorus and nitrogen which are both important for plant growth and transfer them to their plant hosts in return the plants transfer their fungal friends between four and twenty percent of their photosynthate the sugars they produce by photosynthesizing this relationship is the backbone of all our forests on earth and without it life on land as we know it may have never emerged but in recent decades scientists have realized it’s not just the individual tree and the fungi that have a relationship sharing resources back and forth but that the trees themselves are connected by this intricate vast network the first inkling that trees might actually work together came in a study in the early 1980s scientists planted pines side by side in a box in the lab then inoculated their roots with the mycorrhizal fungi to establish an underground fungal network then they tagged the photosynthetic sugars produced by the donor pine with radioactive carbon they did this by sealing one plant in a box with radioactive carbon dioxide they then allowed the pine to absorb it and convert it into radioactive sugars through photosynthesis then they placed photographic film over the side of the root box hoping to see where the radioactive particles traveled from one plant to the other or if they traveled at all when they developed the film they saw the path that the charged particles had taken and the path was through the mycorrhizal fungal network traveling from one tree to the other the idea that trees may share resources presented scientists with an evolutionary paradox trees have always been known to evolve by competing not cooperating trees grow tall to reach the most sunlight their roots branch far and wide to suck up the most water those that get shaded or reach less water often don’t survive if trees of the same species or even of different species shared resources scientists would be forced back to the drawing board with their understanding of how trees have evolved and this idea is what got researcher suzanne simmered excited in one of her early experiments she looked at nutrient exchange between douglas fir trees and paper birch trees two different species that grow together in forests and sometimes compete for space and light she planted fur birch and cedar seedlings in a trio she labeled the paper birch with the radioactive isotope carbon 14 and labeled the douglas fir with a stable isotope carbon 13. that way she could tell not only if carbon was moving from birch to fur but could tell if it was moving from fur to birch the cedar plants acted as a control cedar can’t form mycorrhizal networks with the fur or birch for the simple reason that it forms arbuscular mycorrhizae not ectomycorrhizal like the other two if cedar roots acquire any of the labeled sugars created by fur or birch it would mean that they had leaked through the soil not through the fungal network she then covered the fur with a shade tent reducing the amount they were able to photosynthesize if the two trees were linked in a microrizal network cooperating with one another then the surplus of photosynthetic sugars from the birch should flow into the roots of the fur and what she found was that the birch and fir trees indeed share resources in fact the more shade the fur was covered by the more carbon 14 it received from the birch and the cedar did not receive either of the isotopes further experiments showed that these two species are also able to share nitrogen and share resources in both directions depending on the season and conditions the two species exist in an alternate feedback system helping each other when the other needs it allowing them both to remain healthy but it’s not only a matter of sharing resources other experiments have looked at the chemicals trees produce to signal that they’re being damaged by voracious insects pathogens or human activity one experiment looked at tomato plants all linked up through an arbuscular mycorrhizal network when the researchers infested some of the plants with leaf-chewing caterpillars healthy neighbors had activated four defense-related genes within 6 hours in other words they knew trouble was coming and they were preparing for it as it turns out this preparation helped them the plants that had time to produce defensive enzymes against the pests fared better and the caterpillars munching on those second plants didn’t grow as large and there’s also evidence that trees of the same species have some form of kin recognition through their fungal networks they can identify which trees are most closely related to them and direct more resources towards those trees these experiments show us that trees aren’t solitary individuals but live in a cooperative harmony with one another but if they’re so cooperative does this challenge the prevailing theory that cooperation is less important than competition in evolution it might seem like the law of natural selection would cause trees to only compete for resources but their cooperation isn’t purely selfless if neighboring trees die gaps open up in the protective forest canopy with more sunlight the remaining trees can carry out more photosynthesis yes but they’re also more vulnerable more hot sunshine reaches the delicate forest floor heating up and drying out the cool damp evenly regulated microclimate that forest trees need winds are able to penetrate the forest more easily and without neighboring tree crowns to stabilize against it the chance of being uprooted increases reasons like this is why they’ve evolved to help their neighbors trees live longer and reproduce more often in a healthy stable forest and if we can understand this network we can minimize some of the worst impacts that humans have on the planet in her research on tree connection and communication suzanne simmered and her team found that the biggest oldest trees what are called the mother trees are the hubs of these below ground fungal networks they are the most connected nodes in the network of the forest mother trees share their excess carbon and nitrogen through the mycorrhizal network with the understory seedlings which can increase seedling survival in a single forest a mother tree can be connected to hundreds of other trees but the problem is this we’re great at clear cutting and great at clear-cutting mother trees we always either log the entire forest or go for the biggest oldest trees because they’re the most valuable but if too many of these mother trees are logged too many of the nodes removed the forest as a whole will start to decline disease can start to spread insects start campaigns of destruction but with this research hopefully a shift can start to happen understanding that trees in a forest are connected underground to their kin and to their neighbors could change the way trees are logged when forests are harvested the retention of mother trees can provide resilience smaller hope trees can be removed without causing the network to collapse leaving enough hub trees and enough of the mother trees within the network allows for the flow of communication and the trading of resources to continue retaining mother trees can also help the forest regenerate seeds from the mother tree will sprout nearby and are able to quickly tap into the mycorrhizal network and receive resources from their community that boost their chances of survival additionally experiments have shown that the retention of old trees and their extensive networks can reduce loss of carbon from the ecosystem both above and below ground researchers are now investigating how the connections between mother trees seedlings and other plants enhance resilience of the forest community maintaining the network of connections between trees in a forest should help them resist the stress of climate change and recover more rapidly when climate-related disturbances do occur connected forests are better able to cope with climate change and be more productive healthy and diverse our need for trees is not going away anytime soon so learning how to best utilize this resource for its health and ours will be imperative in years to come and now that scientists are starting to have a better understanding of the mycorrhizal network they’re looking for ways to utilize it not just in the forests but in our agricultural fields the majority of staple food crops are known to form relationships with mycorrhizal fungi if the soil is in good enough condition for the fungi to flourish these fungi could provide crops with nitrogen and phosphorus which means the farmers wouldn’t be so reliant on fertilizer it could be a natural scalable and elegant solution to chip away at the damage agriculture causes on the planet while absolutely necessary for humanity agriculture is one of the most damaging things we do to the planet a lot needs to change but on a personal scale it’s sometimes hard to feel like we can make a difference while we may not be able to change land use practices in brazil or influence lobbyists in the u.s the least we can do is try to be responsible in our own lives and until recently i wasn’t really doing that after moving into my own apartment last year i became so bad about wasting food i didn’t know how to grocery shop for one person and would inevitably overbuy and even if my planning was okay sometimes you just need a tablespoon of sour cream for a recipe not an entire container that will sit there and go moldy and this is why i decided to give hello fresh a try i love to cook but was so tired of the food waste i was creating hellofresh gives you pre-portioned ingredients to make quick delicious meals like these little packets of sour cream so not only are you not wasting entire tubs of sour cream you don’t have to fuss with measuring things out i feel like it’s a small thing i can do to reduce my environmental impact and something i can do to care for myself too plus you can easily change your delivery days or food preferences and skip a week whenever you need and on top of this the packaging hellofresh uses to ship your food is also almost entirely made from recyclable and or already recycled material upping your sustainability points so if you’re ready to free up your time eat healthy meals and help the planet go to hellofresh.com and use code realscience12 to get 12 free meals including free shipping that’s almost two weeks of free dinners and if you’re looking for something else to watch right now you can watch our previous video about mad cow disease or watch real engineering’s latest video the truth about biofuels a great video debunking many common beliefs about the biofuel industry you
