MSU research examines how an invasive pest threatens ecosystems and Indigenous basket making traditions
New research from Michigan State University explores the link between the invasive emerald ash borer, ecosystem health, and Indigenous basket making traditions.
The invasive beetles — native to east Asia — were first identified in Canton, Michigan in 2002, and feed on the black ash trees that generations of Indigenous people have used to make decorative and functional baskets. Black ash trees are also critical to wetland ecosystems.
Deb McCullough is a professor of forest entomology at MSU and is a lead author on the study. She has witnessed the destruction of the forests that she studies by the ash borer.
"We've lost a few hundred million ash trees in Michigan alone. As ash borer is expanding and spreading and killing black ash at these incredibly high rates, it's not going to be very long before we run out of black ash," she said. "We're talking about an invader with the potential to come very close to extirpating black ash in less than fifty years."
McCullough said black ash trees are a foundational species in their ecosystems and that their death has a cascading effect.
They have unique adaptations that allow them to thrive in very wet — or hydric — environments: along rivers, lakes, and streams. Their canopy provides crucial shade for other organisms, while the leaves that fall every year provide nutrients to the ecosystem. The trees are also used by nesting and feeding birds. When a stand of black ash dies and is no longer taking up water, it causes the water table of the forest to rise, often drowning out other vegetation.
While the ash borer larvae feed on other ash species, some research has demonstrated that the insect has a strong preference for black ash. This is worrisome for the tribes who have used black ash for centuries.
"Way before this country was even a country, there were Indigenous people, Native American people, First Nations people in Eastern Canada that have always valued black ash as a cultural resource, and in some tribes, even a spiritual resource," McCullough said.
The black ash has certain properties that make it desirable for basket making: individual growth rings of the tree can be separated by pounding the logs, leaving behind thin and flexible strips that are ideal for weaving.
Scientists and indigenous groups have collaborated for years to try to preserve black ash stands and seeds. While complete eradication of the ash borer is difficult, populations of the pest could potentially be isolated and managed with a combination of insecticides and tree girdling.
The insecticides are systemic: they are injected into and taken up by the trees. After the injections, select trees are girdled. Girdling kills those ash trees but leaves them standing. The girdled trees still attract adult EAB which lay their eggs, but when the hatched larvae try to feed on the girdled tree, they consume the insecticide that was injected instead of any live tree tissue. This kills the EAB larvae. These "tree traps" could be strategically placed within black ash stands to reduce the EAB population there.
Other methods of eradication have not stopped the spread of EAB, but the researchers and tribes hope the tree traps could help preserve black ash stands. McCullough said it's not just ecosystems that are at stake:
"Within individual tribes, if your family is a basket-making tribe, that's your identity, and it has been for generations."