At a greenhouse facility in Lawrence, Kansas, hundreds of tubes of soil are crammed into a row of refrigerators and a nearby cold room. Although they are not very noticeable, microscopic beads in the dirt sparkle like jewels when viewed under a microscope. Some resemble amber teardrops, some are lemon yellow, and some are white pearls with brown dots that resemble eyeballs that are staring back at you.

Spores from fungi are these tiny jewels. Jim Bever, a plant ecologist at the University of Kansas and co-curator of the collection, says, "The spores are actually very pretty." Beyond their allure, spores like these could be essential to reviving threatened plants and their ecosystems, whether they are Colombian cloud forest patches, critically endangered tallgrass prairie.

The spores will spawn mycorrhizal fungi, the oldest and most widespread partner of plants — the two have lived and worked together for some 500 million years. Up to 90 percent of plants have mycorrhizae living among their roots (mycorrhizal means root-dwelling). In exchange for food, the fungi help the hosts obtain water and nutrients, ward off pathogens, and improve tolerance to drought. As a community, mycorrhizae form a subterranean pit crew for maintaining plant health, akin to the gut microbiome in the human body.

Today, ecologists like Bever are wielding mycorrhizal fungi as nature-based tools for conservation. Done correctly, they say, inoculation with these fungi can help to revive endangered plants or ecosystems with less reliance on fertilizers and pesticides than other approaches. But there’s nuance: When introduced where they’re not welcome, mycorrhizal fungi can bring unexpected consequences that may take years to recover from.

Seeing plants only from an aboveground perspective without considering the complex dynamics below ground can mean “missing half of the picture,” says Adriana Corrales, a mycorrhizal ecologist at the University of the Rosary in Bogotá, Colombia, and with the Society for the Protection of Underground Networks (SPUN) based in Colombia.

Creating fertile ground

In a healthy environment, plants and their mycorrhizal partners can find each other on their own. But when ecosystems are too degraded and the native mycorrhizae have all but vanished, researchers have to play plant-fungus matchmaker.

Such is the case with the tallgrass prairie ecosystem that once blanketed the American Midwest before the landscape’s transformation into the Corn Belt. In the last few decades, as conservationists try to return these overprocessed croplands to something more like their ancestral states, they’ve discovered that simply planting tall grasses can’t restore natural biodiversity.

Bever’s mycorrhizae efforts started with a rather primitive experiment in 1998. His team salvaged a patch of pristine prairie and sprinkled some of its fungus-containing soil onto tallgrass seedlings in experimental plots of prairie grass. Encouraged by the vigorous seedling growth, the team scaled up their efforts to larger tracts of land across multiple Midwestern states. Over the years, mycorrhizae doubled the amounts of prairie grass foliage and tripled the plants’ survival rate.

But using native soil to inoculate swaths of former prairie isn’t scalable, because that soil is as rare as the few remaining islands of prairie. So Bever’s group cultures the mycorrhizal fungi for their spores. The team stocks a growing collection of around 60 species for cooking up cocktails with which to inoculate plants, and makes them available to anyone interested in restoration, from land managers to farmers to private companies wanting to start their own inoculant stock.

Most mycorrhizal fungi worm their filamentous bodies inside the root cells of plants, but one kind — called ectomycorrhizal fungi — lurks outside the cells, usually close to the root surface. These fungi, which prefer to associate with trees from temperate and boreal forests, may be a last-ditch solution for ancient black oaks in the cloud forests of Colombia. Black oak (Trigonobalanus excelsa) is a relict species that populated the Northern Hemisphere for millions of years; today it grows only in fragmented patches of forest due to logging for timber and clearing for cropland.

When cultivated for conservation purposes, black oak seedlings often struggle to reach maturity. So Corrales’s team turned to the soil beneath the oaks and its 200-plus ectomycorrhizal taxa. In informal trials, black oak seedlings inoculated with the forest soil had much higher survival rates, potentially because of the fungi, says Corrales. Since 2021, Corrales’s team has produced more than 1,200 seedlings for reforestation, some of which have been replanted in deforested land and fragmented patches of oak forests on private grounds.

Fungi are also lending a hand in Hawaii, where many native plants found nowhere else in the world are struggling under the combined threats of climate change, fires, habitat loss and competition with non-native species. Fungal ecologist Nicole Hynson of the University of Hawaii is using mycorrhizal fungi to help critically endangered gardenias, woody trees most famous for their fragrant blossoms that were once woven into leis. In the case of one of the archipelago’s three endemic species, Gardenia brighamii, only 10 or so individuals remain in the wild despite conservationists’ best efforts.

Hynson says that she’s contacted by land managers who have “tried everything in their playbook, and nothing has worked.” But, she adds, “the mycorrhizal portion is potentially the missing link that they haven’t explored.”

Compared with the black oak and prairie initiatives, Hynson’s team is much finickier, feeding their gardenia seedlings with slurries of select beneficial spores, rather than spore-enriched soil. This helps to eliminate pathogen transmission, and mimicking the wild gardenias’ fungal community gives the plants their best chance of long-term survival.

So far, mycorrhizal inoculation looks promising. In early greenhouse experiments, fungi-fortified seedlings grew three times as fast as their uninitiated brethren, according to unpublished data. Hynson hopes that she’s giving young gardenias the best start in life for when they’re eventually transplanted in outdoor restoration sites.