Quick, which is the biggest symbiotic association on Earth? Did you guess the mycorrhizae? They are the huge symbioses between fungi and the roots of most terrestrial plants. Their total size is not easy to measure because not all the fungal filaments in soils are mycorrhizal nor are the mycorrhizal ones always mycorrhizing (a new verb?). Even so, one can make the case that the combined mass of the participating fungi and plant roots is colossal. A friend, the soil microbiologist David Lipson, tells me that the mass of mycorrhizal fungi on the planet is estimated to be somewhere around 1-3 x 1010 tons (that’s between 1.4 and 4 tons per person). We are obviously talking about a topic that deserves much more of our attention than it has received to date.
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