Mushrooms make it rain in the Amazon

By John Upton

It’s not enough for mushrooms to simply produce spores. A little more than one-third of the world’s known fungal species, including mushrooms, puffballs and rusts, use a neat canon-ball trick that sends those spores sailing through the air toward newfound territory.

Clouds forming over the Napo River, Peru / Flickr: Photographer 23

This trick relies on the detonation of a fluid-filled sac to send so-called ballistospores airborne. It turns out that this neat trick not only helps fungus spread: Scientists recently discovered that these explosions may help keep the rain falling over the Amazon rainforest.

Water cannot condense into a rain drop unless it has something solid, a “seed,” to grow around, such as a speck of dust or a grain of pollen. Lawrence Berkeley National Laboratory researchers searching for the seeds that help clouds form in the Amazon think they have found what they were looking for.

They reported in Science late last month that potassium salts coalesced with organic material to form the seeds that create the Amazon’s clouds. Based in part on an abundance of ballistospores in the atmospheres, the researchers think the salts are squirted out when these spores are ejected from fungus during the night.

“The source of potassium could only have been natural forest organisms,” researcher Mary Gilles said in a press release published by the Lab on Monday.

Fungi are already known to play a critical role in breaking down old wood and leaves on the forest floor, recycling the nutrients and making them available for plants and animals; and now it appears that they also help to keep the Amazon wet and rainforesty. A pretty neat trick.

Mushrooms form ballistospores in their gills / Flickr: jo-h