Before the last black ash trees fell to the emerald ash borer's relentless advance, human hands gathered their seeds — an act of foresight that now forms the foundation of a possible return. Researchers at Penn State have spent years decoding the genetic language held within some 35,000 of those preserved seeds, discovering that black ash carries within itself a remarkable diversity of adaptations, shaped by centuries of living in particular climates and soils. Their findings, rooted in science but shadowed by cultural urgency, suggest that restoration is possible — but only if the knowledge o
Scientists map genetic diversity of black ash to rescue species from beetle devastation
Indigenous communities including Wabanaki, Iroquois and Great Lakes tribes face cultural loss as black ash—foundational to basketry and heritage—disappears from landscapes.
Trees growing side by side often produced noticeably different seeds.
Mark
Why does it matter that genetic diversity exists within a single forest, rather than just between forests?
Mimi
Because it means you don't have to search the entire continent to find the seeds you need. Even a single surviving population contains enough variation that some trees will be better adapted to future conditions than others. That's how species survive change—through the raw material of difference.
Mark
The researchers used AI to measure 35,000 seeds. Why not just do it by hand?
Mimi
Speed and scale. By hand, you might measure a few hundred seeds and miss the patterns. The AI let them see what 35,000 seeds revealed—that climate shapes seed traits in consistent, predictable ways. You need that volume to trust what you're seeing.
Mark
If black ash is already gone from most wild forests, what's the point of studying seeds that came from trees that no longer exist?
Mimi
Those seeds carry the genetic memory of how to survive in those places. When you replant, you're not just putting trees back. You're restoring the specific adaptations that made those populations work. A seed from a cold climate carries instructions for thriving in cold. You can't invent that.
Mark
The study mentions that trees from continental climates had better survival. Does that mean we should only replant seeds from those regions?
Mimi
Not necessarily. It depends on where you're planting. If you're restoring a wetland in a continental climate zone, yes, those seeds make sense. But black ash grew across many climates. You need diversity in your restoration, not monoculture. The point is to match seed to place.
Mark
What happens if the climate keeps changing? Will these adapted seeds still work?
Mimi
That's the gamble. The seeds are adapted to the past and present. If conditions shift dramatically, some populations will fail. But the genetic diversity within populations gives natural selection something to work with. Some trees will adapt faster than others. That's why you preserve as much diversity as possible.
Mark
Why do Indigenous communities care so much about black ash specifically?
Mimi
Because it's not interchangeable. The wood has particular properties—flexibility, strength, grain—that make it ideal for basketry. But beyond the practical, it's cultural continuity. The knowledge of how to harvest and weave it has been passed down for generations. Losing the tree means losing a way of being.
The Pulse
- The emerald ash borer has already erased entire wild populations, leaving seed banks as the last living archive of a species that once anchored wetlands and Indigenous heritage alike.
- For Wabanaki, Iroquois, and Great Lakes communities, the disappearance of black ash is not an ecological statistic but the unraveling of a cultural practice — basket-weaving traditions woven across generations — that cannot simply be replanted overnight.
- Penn State researchers used X-ray imaging and artificial intelligence to characterize 35,000 seeds, revealing that trees from warmer regions produce heavier, faster-sprouting seeds while continental climates breed hardier survivors — adaptations that must be matched to the right landscapes in any restoration effort.
- The most surprising finding cut against assumptions: 43 percent of seed trait variation exists within single forests, meaning even one stand of trees holds enough genetic diversity to give natural selection something to work with.
- Three experimental plantings across Pennsylvania, New York, and Quebec are now testing which seeds survive and grow best in their first critical years — a race against time, since black ash takes up to half a century to reproduce.
- Scientists and conservationists warn that rescuing the species will require cross-border coordination between U.S. and Canadian institutions, because the beetle that destroyed these forests has never respected a political boundary.
Before the last black ash trees fell to the emerald ash borer's relentless advance, human hands gathered their seeds — an act of foresight that now forms the foundation of a possible return. Researchers at Penn State have spent years decoding the genetic language held within some 35,000 of those preserved seeds, discovering that black ash carries within itself a remarkable diversity of adaptations, shaped by centuries of living in particular climates and soils. Their findings, rooted in science but shadowed by cultural urgency, suggest that restoration is possible — but only if the knowledge of what these trees were is matched by the will to bring them back across an entire continent.
The emerald ash borer has reduced black ash forests across North America to graveyards, wiping out entire wild populations with a thoroughness that left little behind. What remains lives in seed banks — thousands of seed lots collected before the trees vanished, stored as a kind of genetic insurance. Researchers at Penn State, led by Jill Hamilton and doctoral candidate Kyra LoPiccolo, have spent years asking whether that insurance can actually be cashed in.
Black ash is not a tree easily replaced. It stabilizes wetlands, supports dependent ecosystems, and holds deep meaning for Indigenous communities — Wabanaki, Iroquois, and Great Lakes tribes among them — for whom its wood has been woven into baskets across generations. The beetle's spread has threatened not just a species but a living cultural practice.
The Penn State team obtained more than 700 seed lots from U.S. and Canadian germplasm collections, then used X-ray imaging and an AI model trained on those images to characterize roughly 35,000 seeds without damaging them. What emerged was a portrait of a species shaped by its geography: trees from warmer, drier climates produced heavier seeds that sprouted faster and grew taller in their first year, while trees from regions of extreme seasonal swings showed stronger early survival. These were not accidents — they were adaptations, evidence that black ash had evolved differently across the continent.
The most consequential discovery, however, came from within individual forests. After germinating 22,000 seeds and establishing experimental plantings near Penn State, in Syracuse, and in Quebec City, the researchers found that 43 percent of seed trait variation existed within single populations. Trees growing side by side could produce strikingly different seeds — a reservoir of diversity that natural selection could draw upon as conditions shift.
Published in Annals of Botany, the findings carry a clear message for restoration: seed origin matters. A seed adapted to warmth will not thrive in cold; one shaped by continental extremes may fail in milder ground. Because black ash takes up to 50 years to reproduce, first-year survival and growth become the earliest and most critical signals of whether a planting will endure.
Hamilton described the seed banks as a Noah's Ark for the species — many of the populations now preserved in those collections no longer exist anywhere in the wild. But preservation alone is not enough. The emerald ash borer crossed every border it encountered, and the response must do the same. Sustained collaboration between state, federal, and university partners across the United States and Canada — sharing seeds, science, and strategy — is the only path toward returning black ash to the landscapes, and the communities, that once depended on it.
Across North America, the emerald ash borer has turned black ash forests into graveyards. The beetle, an invasive species, has killed so many trees across such vast territory that entire populations have vanished from the wild. But before those trees disappeared entirely, foresters managed to collect seeds—thousands of seed lots gathered from across the continent and stored in seed banks like a genetic insurance policy. Now, researchers at Penn State have spent years analyzing what those seeds contain, mapping the hidden diversity within them, and asking a crucial question: can we use this knowledge to bring black ash back?
Black ash is not just another tree. It stabilizes wetlands, holds soil in place, and supports the creatures that depend on those ecosystems. For Indigenous communities—Wabanaki, Iroquois, and Great Lakes tribes among them—it is irreplaceable. The wood has been woven into baskets for generations, a practice that carries cultural weight and identity. As the beetle has spread, that heritage has been threatened with erasure.
The Penn State team, led by Jill Hamilton and first-authored by doctoral candidate Kyra LoPiccolo, took on a massive undertaking. They obtained more than 700 seed lots from the U.S. Department of Agriculture's National Plant Germplasm Network and Canada's National Tree Seed Centre. Using X-ray imaging, they looked inside seeds without damaging them, measuring their form and structure. They then trained an artificial intelligence model on those images to automate the process, ultimately characterizing approximately 35,000 seeds. The work revealed something striking: black ash seeds vary enormously depending on where the parent trees grew. Trees from warmer, drier climates produced heavier seeds that sprouted faster and grew taller in their first year. Trees from continental climates—places with extreme seasonal swings—showed better survival rates and faster early growth. These were not random differences. They were adaptations, evidence that black ash populations had evolved to thrive in their particular corners of the continent.
But the most important discovery lay within individual forests. When the researchers germinated 22,000 seeds and established three experimental plantings—one near Penn State's campus, one in Syracuse, New York, and one in Quebec City—they found that 43 percent of seed trait variation occurred within single populations, not between them. Trees growing side by side often produced noticeably different seeds. This meant that even a single forest contained substantial genetic diversity, raw material that natural selection could work with if conditions changed. That diversity is now the foundation for any restoration effort.
The team published their findings in Annals of Botany, and the implications are clear. When the time comes to replant black ash across North America, seed selection will matter enormously. A seed from a warm climate will not thrive in a cold one. A seed adapted to continental extremes may fail in a milder region. The researchers used first-year survival and growth as early indicators of fitness, knowing that trees take up to 50 years to reproduce. What happens in those first months and years will determine whether restoration succeeds or fails.
Hamilton called the seed banks a "Noah's Ark for black ash." Many of the populations represented in those collections no longer exist on the landscape. The beetles have seen to that. But the genetic material remains, preserved and now understood. What comes next requires something the trees themselves cannot do: cross-border collaboration. The emerald ash borer does not recognize political boundaries, and neither should the response. State, federal, and university partners across the United States and Canada will need to work together, sharing resources and knowledge, to devise a plan that can rescue black ash across its entire range. Without that coordination, without sustained investment in understanding tree genetics and pest resistance, the species that once anchored wetlands and carried cultural meaning will remain a memory.
Notable Quotes
We like to consider this a little bit like Noah's Ark for black ash. Many of the populations represented in these collections are trees that don't exist on the landscape anymore.— Jill Hamilton, Penn State associate professor and study senior author
Even trees growing side by side often produced noticeably different seeds. This is important because it means each population contains a lot of genetic diversity, which gives natural selection raw material to work with if environmental conditions change.— Kyra LoPiccolo, doctoral candidate and study first author
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