Reviving the “Functionally Extinct” American Chestnut
▼ Summary
– The American chestnut, once a dominant Appalachian forest species, was nearly eradicated by invasive Asian fungal pathogens, with an estimated 3 billion trees killed.
– The species persists outside its native range in drier western areas and through saplings that sprout but typically die before reproducing due to the persistent fungus.
– Researchers are using modern genomic techniques and extensive testing to find the best methods for restoring the chestnut to its original ecosystem.
– Potential restoration paths include breeding from large surviving trees (LSACs) that show natural resistance and utilizing a virus that attacks the blight fungus.
– Successful restoration may depend on interbreeding resistant trees to create a strain that can both survive the pathogens and thrive in the Appalachian environment.
The majestic American chestnut, once a towering giant of the Appalachian forests, was nearly erased from existence by invasive fungal blights. Today, this iconic tree is considered functionally extinct, no longer shaping the ecosystem it dominated for millennia. Yet, a determined coalition of scientists and conservationists is leveraging cutting-edge genetics and traditional breeding to orchestrate a remarkable comeback, aiming to restore the chestnut to its native hills.
Several promising strategies are emerging in the fight for restoration. While the blight fungus thrives in the warm, humid conditions of the eastern United States, American chestnuts planted in the drier climates of the Pacific Northwest have continued to grow healthily. This demonstrates the species can still prosper outside the pathogen’s ideal range. Furthermore, a curious natural phenomenon offers a glimmer of hope: a virus that attacks the blight fungus itself allows a scattering of trees to survive in areas where this virus is present.
Perhaps most intriguing are the rare large surviving American chestnuts (LSACs) found within the tree’s original territory. These mature individuals, which somehow reached adulthood despite the pervasive blight, hint at a possible genetic legacy of natural resistance within the historic population. Researchers are intensely studying these survivors. The goal is to crossbreed them, combining any distinct resistance traits to develop a new generation of trees robust enough to withstand the fungi and flourish once again in Appalachian soils.
This work is painstaking, given the tree’s long growth cycle, but a recent scientific publication details the application of modern genomic tools to accelerate the process. By meticulously mapping genes and conducting exhaustive field tests, teams are identifying the most effective genetic pathways to blight resistance, whether found in rare American specimens or carefully introduced from related Asian chestnut species. The revival effort represents a multifaceted mission, blending deep ecological understanding with advanced biotechnology to return a foundational species to the forest.
(Source: Ars Technica)
