Fungi are odd lifeforms, indistinguishable from plants for most people. Indeed, certain types are edible and even enhance some of our favorite foods – Roquefort, anyone? However, like plants and animals, fungi form their own kingdom of an estimated five million lifeforms (though under 200,000 are identified).
When we hear the word fungi, mushrooms often leap to mind. But those are just a single example (like yeast and mold), and most fungi remain invisible subterranean denizens of the forest. Most of them are decomposers, leeching nutrients from other lifeforms for food. But some have unique properties that react chemically with other lifeforms, changing their behavior. Scientists are just starting to understand how vital fungi are for Earth's ecosystem.
Fungi Have a Complicated Relationship with Atmospheric Carbon
Those of us who remember high school bio know that photosynthesizing plants take CO2 from the atmosphere, gobble up the carbon, and breathe fresh oxygen back out for us to enjoy. The carbon forms part of the plant's structure and, when the plant dies, part of the soil. Right? Not necessarily.
Fungi complicate things. From what scientists have been able to determine, they have a highly variable and poorly understood relationship with the carbon cycle. The two most significant downsides to this are -
They could be making climate change worse!
None of our predictive climate models account for fungi.
For example, mushrooms growing on dead trees will take carbon (among other things) from them, change it back into C02, and breathe the greenhouse gas back into the atmosphere. This process, and similar ones on the part of fungi, may partially account for the highly variable ability of plants to either sequester or emit carbon.
Even Forests Have Variable Sequestration Rates
Well, since fungi may be unreliable in the fight against climate change, at least we have the forests. Despite the egregious amounts of CO2 we emit daily, not all of it remains in the atmosphere for a long time, thanks to trees' ability to pull it from the atmosphere and store it.
Forests can absorb about a third of all human CO2 emissions at current rates, using it as plant food. So the longer carbon remains in the woods, as plant matter or sequestered in the soil, the better for the environment.
But scientists have noticed that similar to soil, forests have highly variable abilities to absorb atmospheric CO2. Much of this variation is due to temperature. As forests get warmer, their ability to absorb and store carbon decreases.
Since we know that the most common home of fungi is the forest floor, does that mean that they, too, are reducing the ability of forests to act as carbon sinks and even turning some into net emitters? Again, not necessarily.
Mycorrhizal Fungi Supercharge the Carbon Cycle
Forests are enduring bastions of biodiversity, hosting a complex web of symbiotic life that makes them robust and adaptable. For example, fungi dwell on the roots of over 90% of plants worldwide, sending out filaments through the soil that pull in nutrients and direct them back to the host plant. These filaments are so fine that one meter of soil can contain up to 12,000 miles of them.
As it turns out, mycorrhizal fungi play a role in 85% of plant life and often inhibit decomposition. Unlike the surface-dwelling variants that emit CO2, these root dwellers make plants even more effective at sequestering carbon, supercharging their ability to stave off climate change. This effect is so pronounced that forests with high levels of mycorrhizal fungi are the most effective at pulling CO2 from the atmosphere. Essentially, they are the hero fungi who may be our biggest ally in the battle against carbon emissions.
Too Much Nitrogen Poses a Threat to Climate-Friendly Fungi
Unfortunately, mycorrhizal fungi are under threat. This is because they are particularly vulnerable to excessive soil nitrogen. Nitrous oxide, like CO2, is a GHG that humans emit in large quantities. In addition, natural and synthetic fertilizers, often appearing in conjunction with widespread deforestation, cause high-nitrogen runoff that upsets the nutrient balance in forest soil.
We Must Avoid Synthetic Fertilizers and Deforestation
Atmospheric nitrogen has fallen over the last several decades in the US. This positive trend results from employing nitrogen scrubbers, using less industrial fertilizer, and the increasing proportion of green energy sources. This is excellent news for the ability of North American forests to absorb and sequester carbon.
However, developing nations are increasing their nitrogen pollution, mainly through the fertilizer needed to feed growing populations. The effects of this process are especially pronounced in Amazonia, where deforestation continues. That said, supporting global initiatives to reduce nitrogen pollution will go a long way toward preserving mycorrhizal fungi and their essential role in absorbing CO2.
Mycorrhizal Fungi Are a Precious Resource for Climate Preservation
The diversity of the fungi kingdom makes it no surprise that individual species fall on different sides in the struggle for the environment, at least concerning carbon absorption and sequestration. However, the shocking prevalence of mycorrhizal fungi on the roots of so many plants worldwide is a massive benefit to the ability of forests to do their critical work for the atmosphere.
Although mycorrhizal fungi are vulnerable to nitrogen pollution, affluent nations have made progress in that area, making it easier for their forests to remain efficient carbon sinks. But there are still many opportunities to improve worldwide. Given all the uncertainty about how fungi work in their environment, one thing is sure: they have an essential and complex role in the global carbon cycle that scientists have only now just begun to understand.
Key Takeaways
Tend Your Garden – Chances are that fungi keep most plant species in your garden healthy. When you care for the garden, you promote this beneficial symbiosis. So irrigate well without disturbing the soil, and refrain from synthetic fertilizers containing too much phosphorus and nitrogen.
Mulch – Mulch provides protection and habitat for fungi as it decomposes. Wood-chip mulch is excellent around the base of trees, while leaf and other organic mulch are perfect in plant beds.
Don't Choose a 'Cide – Fungicides are a no-no. But herbicides and pesticides are also harmful and can kill the beneficial fungi that help keep your plants healthy. You are better off using organic or alternative pesticides to keep the animals and insects away.
