How a gigantic fungal network orchestrates a circle of life
The quest by evolutionary biologist Toby Kiers to stick her nose in the earth has taken her to the world’s remotest island.
Toby Kiers, an American evolutionary biologist, loves to stick her nose in the earth – literally – to sniff out its secrets: she is on a mission to chart a vast fungal network she believes is key to the health of our planet.
This quest recently took her to the world’s remotest island, a coral atoll in the middle of the Pacific. She and two British colleagues were the first scientists to explore its underground realm of tangled filaments.
They have uncovered evidence of a symbiotic fungal network that harvests nutrients from bird droppings, which it feeds to trees in exchange for the carbon it needs to survive. Making this “trade” all the more extraordinary is the apparent capacity of the network to increase or diminish supply on demand.
Kiers, 46, a professor at the Amsterdam Free University, believes protecting the “woodwide web” is essential to fight climate change.
She shared her preliminary findings with The Sunday Times after returning with soil samples – now under analysis – from the uninhabited Palmyra atoll 1600km south of Honolulu, the Hawaiian capital. It is so remote that most of its seabirds may never have seen humans.
The network of lagoons and islets covering some 19sq km is part of a “marine national monument” monitored by the US Fish and Wildlife Service and the Nature Conservancy, a global organisation based in Virginia.
The tropical forest, powder-white beaches and coral reefs are of interest to scientists as a uniquely pristine environment.
It took Kiers and British biologists Stuart West and Charles Cornwallis four years to get all the permits they needed to visit.
On arrival they had to put their clothes in a freezer for 24 hours to avoid importing alien life forms that might alter the ecological balance. “It was like going to Mars,” Kiers said.
They braved shoals of baby blacktip sharks as they waded through parts of a lagoon too shallow to enter by boat.
The “dominant terrestrial player”, as Kiers put it, is a fearsome-looking creature, the coconut crab, which can live for 60 years, growing up to 4kg and one metre across from one leg to another. “Picture a spider-like crab as large as a rubbish bin lid with human hand-sized pinchers,” said Alex Wegmann, lead scientist for the Nature Conservancy and its former Palmyra director.
Kiers believes the crabs play a role in a hitherto unknown type of “nutrient cycling” that goes on around the pisonia trees, also known as “bird-catcher” trees because of their sticky seeds, which attach themselves to feathers in what is thought to be nature’s way of dispersing them to other islands.
At the centre of this cycle is the vast fungal network that supplies its partner trees with nutrients such as phosphorus from guano (excrement) deposited by a screeching horde of red-footed boobies, sooty terns and frigate birds. Some of this guano then seeps into the sea where it nourishes the coral.
The crabs dig their burrows under pisonia trees.
“We think they are helping to introduce the fungi shoots to new tree roots through their digging,” Kiers said.
“The fungi control the nutrient supply between the rainforest and the coral reef.
“They are essential for the trees to grow. If the trees grow, the birds come and nest. If the birds come, the reef benefits from ‘pulses’ of nutrients.
“Over millions of years an intricate opera of interactions has evolved – we are discovering how the hidden players, like the fungal networks beneath the surface, keep these interactions in tune.”
With her Society for the Protection of Underground Networks, Kiers wants to create an atlas of all the underground fungal systems. Next month she will visit Lesotho in southern Africa to sample the dirt there.
“Once you begin to follow the world of fungi, obsession quickly follows,” she said.
The Sunday Times
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