Untold Earth

(gentle upbeat music) - [William] Mushrooms are like the Hooked on Phonics of ecological literacy, and I think that truffles have some of the coolest lessons.

- We're dealing with chemical powerhouses.

They're producing such powerful chemistry that animals can find them from meters away.

- [James] And here's the part of the cycle that needs to be spoken delicately.

The animal poops the spores.

(inquisitive music) - [Narrator] In kitchens around the world, truffles represent culinary excellence and prestige.

But in the forest, they're kind of just crap.

(gentle upbeat music) While truffles may not be as appetizing in their natural habitat, they're actually even more miraculous.

Could these tiny poop mushrooms be key to the survival of the forest ecosystem at large?

(inquisitive) (inquisitive music) - We are in the Oregon Coast Range.

This is probably the most productive area in North America for truffles of all kinds.

It's Douglas fir forest.

This particular stand of trees was an old pasture, and this is the kind of environment where the Oregon truffles thrive.

They're in these human habitats.

(inquisitive music) A truffle is a mushroom that typically fruits underground.

Unlike a mushroom that can discharge it spores into the wind, truffles lack that ability to discharge their spores and instead produce powerful aromas that can attract animals to come eat them.

- They smell a truffle and they say, "Aha, there's lunch."

But the spores don't get digested.

They hit the ground and this little pile of spores, surrounded with some unsavory leftovers of the truffle, they get washed into the soil by rains and start new colonies.

- When you look around, there isn't a lot for a mammal to eat in a forest like this.

There's seeds from the trees and the occasional plant on the ground.

But most of the year there isn't a lot of calories to be found except these truffles, which are all edible, and probably represent the most important source of both calories and protein for most of the forest mammals.

In some level, they form the connection between the plant life and the animal life in the forest.

(inquisitive music) (inquisitive music) To understand the aroma of truffles, you have to kind of think of the challenge from the truffles perspective.

Here it is, six inches underground, in this wet cold soil in the middle of the winter, and somehow it has to attract the attention of an animal, that may not even be nearby, to come find it and eat it.

So to do all of that, the aroma has to achieve several things.

It cannot be water soluble or it would just soak into the soil.

So it has to be a fat soluble aroma.

It has to be volatile at very low temperatures so that it's giving off that aroma even when it's cold out.

And then it has to be strong enough that an animal can detect it from 100 feet away or more, and then also compelling enough to get the animal to change what it's doing and come find it and eat it.

Truffles have achieved those objectives in various ways.

The famous European truffles produce thiols and mercaptans which are like rotten egg smell, they're skunk.

Our sense of smell is very sensitive to those compounds.

And then they are known to incorporate pheromones in their aroma, which as we know, are capable of influencing our behavior.

So in all those ways, truffle aroma is just really designed for the situation where they're living.

(inquisitive music) Oh, look, Luca's got one over there.

Did you notice how far away he was tracking this one?

- [William] Mm-hmm.

- He's like 50 feet away.

(laughs) (inquisitive music) - Most plants in the world have fungal partners.

Here, in these forests, they have a special type of fungal partner called an ectomycorrhizal fungal partner.

- Ecto meaning outside and mycorrhizal meaning that they have an association with the roots of trees.

- We think of tree roots as the part of the plant that does all the nutrient acquisition.

But under the microscope, those fine roots are completely covered with fungus, to the point where the part of the tree that does the nutrient acquisition actually has no contact with the soil at all.

So all of the nutrient exchange and water exchange is mediated by this fungus.

- So there's an exchange going on, then fungus, phosphate and other nutrients to the tree, tree back to the fungus with sugars.

And this has become, over millions of years of evolution, an absolutely essential symbiosis.

(inquisitive music) Some fungi are specific to certain trees.

There's a wide range of truffles that we find only with Douglas fir.

If a fungus is specific to a host, our hypothesis is that that more specific kind of association will give that group of trees an advantage over other combinations of fungus and trees.

(inquisitive music) - So for part of my thesis, I set up a greenhouse experiment in which I had Douglas fir seedlings.

And what we're seeing on these roots is that the majority of them are colonized by Rhizopogon, and this is a genus of truffle.

When the seedling germinates, the Rhizopogon will find its root tips.

And it has been shown to enhance seedling survival and even tolerance to drought.

(inquisitive music) (gentle upbeat music) - Disturbance in any ecosystem benefits some things at the expense of others.

The question isn't whether something is always harmful or always beneficial, it's what does it harm and what does it benefit.

We have a working example of a place that had been grazing cattle right up to the stream, eating all the vegetation.

Over time, the cattle were removed and the site was planted with Douglas fir and the trees grew up and started producing a phenomenally lucrative crop of truffles.

At the same time, they're helping the trees.

So it's a real win-win for both commercial agriculture, and then of course, while the trees are standing, they're sequestering carbon, and they do all of the things the trees do for the natural environment- providing habitat for all sorts of wildlife, generating oxygen, cleaning the air and water.

(gentle upbeat music) - The current cultural perspective is like truffles are a high-end ingredient, something of high class society.

And I think that the more that we show people that there's something to value in nature, something that's upholding the cradle of our environment, I think that truffles are gonna be a key proponent in helping us to protect the environment.

And then there's just that add-on in the fact that they can help to stimulate the economy.

So when we can see more small producers are able to make a living with truffle cultivation, I think that there'll be more ammunition in the political forum to be able to protect the environment.

(gentle upbeat music)