Ash trees are unlikely to go completely extinct, but they are closer to that edge than most people realize. Five of the six most prominent ash species in North America are classified as Critically Endangered, one step from extinction on the IUCN Red List. The sixth is listed as Endangered. The cause is a single invasive insect, the emerald ash borer, which has already killed hundreds of millions of ash trees across the United States and continues to spread.
The more realistic outcome is not total extinction but something called functional extinction: ash trees become so rare in the wild that they no longer play a meaningful role in their ecosystems. Whether that happens depends on a handful of conservation efforts now underway, including breeding programs, biological controls, and a small population of naturally resistant trees that scientists are racing to understand.
How the Emerald Ash Borer Kills Trees
The emerald ash borer (EAB) is a metallic green beetle native to Asia that likely arrived in the United States during the 1990s, hidden in wood packing materials. The adults aren’t the problem. It’s the larvae, which hatch beneath the bark and feed on the inner tissue that transports water and nutrients. This feeding essentially strangles the tree from the inside out, cutting off its circulation. A single tree can die in as little as two years. An entire stand of ash can be wiped out within five.
The mortality rate of infested ash trees is nearly 100 percent. Forest Service models have used a 100 percent host mortality assumption, and real-world observations support it. One projection estimated that EAB could eliminate ash from forests across 20 states by 2050.
How Many Trees Are at Risk
Green ash, white ash, and black ash are the three most common species in North America, together accounting for nearly nine billion trees in the forested lands of the contiguous U.S. Hundreds of millions have already been killed since the beetle was first detected near Detroit in 2002. The insect spreads at roughly 20 kilometers per year, and it has now been confirmed in more than 35 states and several Canadian provinces.
Black ash is the most vulnerable species. By 2035, EAB is expected to affect about 75 percent of its native range in the eastern United States and Canada. Black ash tends to grow in wet, low-lying areas where few other hardwoods thrive, so its loss leaves gaps that are especially hard for forests to fill.
In cities, the financial toll is staggering. Removing and replacing dead urban ash trees could cost municipalities more than $12 billion nationwide.
The 1 Percent That Survived
In areas where EAB swept through years ago and killed virtually everything, a very small number of ash trees are still standing. A 2010 survey along 10 kilometers of floodplain forest in northwest Ohio, where most ash had died by 2008, found that 2.6 percent of ash trees were still alive. Only 1 percent were actually healthy.
Scientists call these survivors “lingering ash,” and they represent the best hope for the species’ long-term future. The open question is whether these trees carry genuine genetic resistance to the beetle or whether they simply haven’t been found yet. Research is ongoing to determine if resistance traits can be identified, isolated, and bred into future generations of ash. If even a fraction of these survivors are truly resistant, they could become the foundation for restoring ash populations across the continent.
Biological Controls and Conservation
Since EAB cannot be eradicated at this point, the strategy has shifted to slowing it down and building resilience. One major effort involves releasing tiny parasitoid wasps from the beetle’s native range in Asia. These wasps don’t sting humans. They target EAB at different life stages: one species can parasitize up to 90 percent of EAB larvae in a given area, another kills up to 50 percent of larvae, and a third destroys up to 60 percent of EAB eggs. Federal agencies have released these wasps at sites across the country and monitored their establishment for years afterward. The goal isn’t to eliminate EAB entirely but to reduce beetle populations enough that ash trees, especially resistant ones, can survive and reproduce.
The U.S. Forest Service has also been banking ash seeds and genetic material from trees across the country. The collection strategy aims to gather seeds from at least 50 trees per ecoregion for each species, preserving genetic diversity even if wild populations collapse. Each tree typically yields between 2,500 and 12,500 seeds. These seed banks function as an insurance policy: if wild ash disappears from a region, stored seeds could eventually be used for replanting, ideally with stock bred for beetle resistance.
What Forests Look Like Without Ash
Forest Service modeling from 2010 to 2060 suggests that in most non-urban forests, the loss of ash will not cause a dramatic ecosystem collapse. Ash typically makes up a small percentage of total forest composition in the Midwest and Northeast, and other tree species gradually fill in the gaps. The transition takes decades, but forests do recover in terms of overall canopy cover and wood volume.
The exceptions matter, though. In wetland forests where black ash dominates, there are few species ready to take its place. These areas can shift from closed-canopy forest to open marshland, fundamentally changing the habitat for birds, insects, and other wildlife. Urban and suburban areas also suffer disproportionately because ash was planted heavily as a street and park tree in many American cities, sometimes making up 20 percent or more of the urban canopy.
Cultural Loss for Indigenous Communities
For many Native American and First Nations communities, the decline of black ash carries a weight that goes beyond ecology. Black ash is considered a keystone cultural species for tribal nations across the United States and Canada. Tribes have used it for thousands of years to make baskets, and basketmaking is deeply tied to identity, self-expression, and community structure, particularly among Anishinaabek tribes in the Great Lakes region.
The cultural connections run even deeper than craft. In Ojibwe tradition, black ash is linked to the story of Black Elk and a sacred tree. In Wabanaki creation stories, brown ash (another name for black ash) is the tree from which people originated. Researchers have explored alternative materials for basketmaking, but as one Forest Service scientist put it, there are culturally no substitutes for black ash. Tribal nations and the Forest Service are now collaborating on conservation efforts, but the timeline is working against them as EAB pushes deeper into black ash territory.
Protecting Individual Ash Trees
If you have an ash tree on your property, it can be protected with insecticide treatments, but the commitment is ongoing. Professional treatments typically cost around $0.80 to $2.40 per centimeter of trunk diameter per year, depending on the method and location. For a large shade tree with a trunk roughly 50 centimeters across, that could mean $40 to $120 annually, every year, for the life of the tree. Soil injections tend to be cheaper than trunk injections but may be less effective on very large trees. Treatment makes sense for healthy, high-value trees in areas where EAB has been detected but hasn’t yet caused significant damage. Once a tree has lost more than half its canopy, treatment is unlikely to save it.
Will Ash Trees Survive as a Species?
Total extinction of ash in North America is unlikely. Seed banks preserve genetic material, some trees show natural resistance, and biological controls are reducing beetle pressure in certain areas. But the wild ash forests that once stretched across the eastern half of the continent will look very different in 30 years. Models project that ash could functionally disappear from forests in 20 states by 2050 without intervention.
The realistic best-case scenario is that resistant trees are identified, bred, and eventually reintroduced into the landscape over a period of decades. The worst case is that the lingering survivors turn out to be lucky rather than genetically resistant, and ash becomes a tree that exists primarily in managed settings: arboretums, seed vaults, and the occasional chemically protected yard tree. The species would persist, but its role in American forests and indigenous culture would be fundamentally diminished.