During 1904’s summer, American chestnut trees in the Bronx experienced distress. Their typically vibrant green and slim leaves began to yellow and curl. Rust-hued markings appeared on some trunks and branches.
By the subsequent summer, the chestnut trees in what is now known as the Bronx Zoo were either dying or already dead. Circa 1940, nearly all American chestnuts in their native eastern U.S. habitat had vanished.
The root cause was a tiny adversary: Cryphonectria parasitica, the fungus behind chestnut blight. This fungus was unintentionally brought over with Japanese chestnut trees.
Upon its introduction in the U.S., it rapidly disseminated, pushing the American chestnut (Castanea dentata) to near extinction. Today, while some continue to sprout, they emerge from the living roots of previously fallen trees and are fated to perish due to the persistent fungus. Thus, they can never grow to their former majestic heights, comparable to nine-story buildings.
The downfall of the American chestnut underscores the havoc fungi can wreak. In her recent work, “Blight: Fungi and the Coming Pandemic,” Emily Monosson delivers a compelling and occasionally unsettling narrative on fungal diseases menacing pines, bananas, frogs, bats, and increasingly, humans.
However, not all fungi are villains. As Monosson notes, the majority are life-sustaining, recycling crucial nutrients by breaking down deceased entities. However global travel and trade expose new territories and species to foreign fungi, leading to potentially lethal outcomes.
The book’s initial section delves into this issue, starting with an urgent question: Are humans at risk from fungi? Thankfully, as Monosson explains, our body temperatures are inhospitable for most fungi. Yet, climate change might force some fungi to evolve for warmer environments.
For instance, Candida auris, a recent fungal threat to humans, is proliferating in medical settings. Similarly, other infections might find new habitats due to rising temperatures.
Monosson vividly describes fungal epidemics in various species, underscoring their potential devastation. For example, Fusarium wilt endangers our primary source of yellow bananas. U.S. caves are strewn with bat remains, decimated by the Pseudogymnoascus destructans fungus responsible for white nose syndrome.
The chilling decline of frog populations in Central America and beyond, due to Batrachochytrium dendrobatidis, or chytrid, horrifies experts. This segment made me despair, reminiscent of HBO’s “The Last of Us” series.
However, as Monosson suggests, nature might have ways to counter these threats. Some species show signs of adaptation against these fungal adversaries. It’s crucial to note that pathogens don’t necessarily become gentler; they evolve to propagate.
Encouragingly, some frog groups previously decimated by chytrid are rebounding. For instance, in Yosemite National Park, chytrid-infected frogs display no symptoms. Certain whitebark pine trees in the western U.S. even possess resistance genes against the longstanding white pine blister rust disease.
Humans are also intervening. Considering our inadvertent role in exacerbating fungal diseases, perhaps we bear a responsibility, posits Monosson. Initiatives like nourishing bats during autumn might help them endure the fat-depleting white nose syndrome through winter.
There are also ongoing efforts, to harness natural resistance, to rejuvenate American chestnuts. Monosson envisions a future where these modified chestnuts might thrive once more, coexisting with oaks and hemlocks.