After an asteroid, a volcano or a nuclear weapon, mushrooms could save humanity

Raphael Manet monitors the growth of oyster mushrooms at the "Bunker Edible" (bunker edible) in Strasbourg, France, on February 19, 2018. The organic farm was established in a former spice powder bunker used during the Franco-German period. War of 1870.Vincent Kessler / Reuters

• In a new book, writer Bryan Walsh outlines strategies likely to keep people alive after a disaster, such as an asteroidal impact, a supervolcan eruption or a nuclear war.
• Walsh suggests that because mushrooms, rats, and some insects can thrive without sunlight, humans could begin to grow them with the remains of dead trees after an apocalyptic event.

• Visit the Business Insider home page for more stories.

About 66 million years ago, an asteroid collapsed into the earth 's atmosphere and crashed into the seabed, creating an explosion over 6,500 times more powerful than the nuclear bomb that the United States dropped on Hiroshima.

The impact sent clouds of debris and sulfur into the Earth's atmosphere, blocking the light and heat of the sun for about two years. Photosynthesis stopped, which prevented the growth of plants. The surviving dinosaurs died of extinction.

But the fossil record shows that the mushrooms have prospered as a result.

According to TIME science journalist and editor Bryan Walsh, mushrooms are essential for human survival if such an apocalyptic event occurs in the future.

Walsh's new book, "End Times," examines how catastrophic events, natural or man-made, threaten our existence. He points to three types of potential disasters – asteroid impacts, supervolcan eruptions and nuclear war – all of which have one thing in common: they could end up blocking the sunlight needed to feed the plants.

"Erase the sun, and even the best-prepared survival specialist, a desert master, will starve with everyone else," writes Walsh in the book.

To survive, he says, people should adopt sunless farming – growing mushrooms, rats and insects.

Asteroids, supervolcans and nuclear wars could block the sun

The mushroom of the Castle Bravo nuclear test of March 1st, 1954.NOAA

Research suggests that the consequences of supervolcan eruptions and nuclear bombs could be similar to the consequences of the asteroid that condemned the dinosaurs.

About 74,000 years ago, for example, the eruption of the Toba supervisolcan sent clouds of sulfur dioxide into the atmosphere, reducing the sunlight by 90%. According to one analysis, this volcanic winter may have reduced the world's human population to only 3,000 people.

If enough nuclear bombs (thousands) explode, it could also lead to a nuclear winter reducing sunlight levels by more than 90%, according to an article written in 1983 by Carl Sagan. Global temperatures could drop to 45 degrees Fahrenheit in this scenario.

"Such rapid and radical cooling could make agriculture impossible, even in regions spared by missiles," writes Walsh.

The eruption of Mount St. Helens in 1980 killed 57 people and caused billions of dollars in damage. The Toba super-eruption was equivalent to 2,800 eruptions at Mount St. Helens.AP

In other words, without sun, our food system would degrade.

The solution for growing mushrooms in Walsh's book comes from David Denkenberger, a civil engineer who suggested it in a 2014 book on post-apocalyptic agriculture, titled "Feeding Everyone, Nothing." to do."

"Maybe when humans disappear, the world will be ruled by mushrooms again," Denkenberger told Walsh. "Why not just eat mushrooms and not disappear?"

Mushrooms grow on trees, with or without sun

A field of almond trees dead after a drought is sighted in the Central Valley of California on May 6, 2015.Lucy Nicholson / REUTERS

If clouds of debris or ashes were to clear the sun and cool the climate quickly, trillions of trees would die. Humans would not be able to digest this dead wood, of course, but mushrooms could not – no photosynthesis required.

Walsh does the math: a log 3 feet long by 4 inches wide should produce 2.2 pounds of mushrooms in four years, according to his calculations.

It does not seem like much, but with a small population after a disaster and an effective mushroom production, Denkenberger thinks it could work.

The oyster mushrooms grow in a substrate block at the "Bunker Edible" (the "edible bunker") in Strasbourg, France, on February 19, 2018.Vincent Kessler / Reuters

While we use wood to grow mushrooms, we could also use the leaves of dead trees, he said.

"The crushed leaves could be turned into tea to provide the missing nutrients such as vitamin C, or used to feed ruminant animals such as cows or rats," Denkenberger told Walsh.

Dead trees can feed other life forms, such as rats and insects

Rats, just like mushrooms, can digest cellulose, the sugar that makes up 50% of the wood. Thus, whatever the mushrooms leave could be fed to rats, suggests Walsh. In this way, all human survivors could eat meat.

Rats are trapped in a cage at Vertou, near Nantes, June 5, 2019.Stéphane Mahe / Reuters

In addition, rats breed quickly and they probably do not need sunlight to do so, adds Walsh. It takes only six weeks for a rat to reach sexual maturity, then 70 days to produce seven to nine babies. According to Denkenberger's calculations, all of humanity could eat rats after only two years.

Insects could also provide protein, and many of them would survive a solar disaster.

"The same qualities that make insects so abundant and persistent would allow many species to resist even the most extensive and climatic existential disasters," writes Walsh. "Beetles can feast on dead wood, and humans can feast on beetles."

People taste pralines of mealworms.REUTERS / Jerry Lampen

Insects are already a staple in some parts of the world and are starting to gain ground elsewhere. Walsh describes an insect fair held in Richmond, Virginia, where he tasted a pasta dish with ground cricket dumplings, called "Orthopteran Orzo" and fried mealworm larvae.

"They were both passable," he writes. "If I were hungry, though, I would manage."

Survivors would regroup

Walsh's book refutes another popular idea of ​​how to feed us during an apocalypse: cannibalism.

This would be of no help in the aftermath of a disaster that would put humans at risk of extinction, he says, because other people are just not a sustainable food source. Walsh refers to a 2017 study in which a group of undergraduate students calculated the lifespan of the human species if we lived only through cannibalism. They found that there would only be one person after 1,149 days (about 3 years).

He adds, however, that the creation of a new farming system would require collaboration. He thinks such collaboration would be likely in the event of a disaster.

Women work in a cabbage field at Fundo Aracal, expropriated, in the state of Yaracuy (Venezuela), August 27, 2007.Reuters

"Despite all our fears as to what would come next, all our dark stories, collapse and conflicts are not consequences after a disaster," writes Walsh. "Human beings help each other, even in times when it does not seem to be in their interest, and it is probably that Homo sapiens survived its closest disappearance – the super-eruption of Toba – and that's the only way to survive the next one. "