Green ash / Fraxinus pennsylvanica

People tend to think of trees as strong. They are tall, long-lived and deeply rooted. We see their branches waving during a storm, capable of resisting tremendous wind stress. Wood alone carries connotations of strength. While it isn’t obvious just by looking at it, this green ash tree is on life support, kept alive through chemical treatment. It has been treated with emamectin benzoate so that it can resist the emerald ash borer, an invasive beetle that threatens all ash trees on our continent. Ongoing treatment will be required for the rest of this tree’s life.

This and other ash trees marked with an orange band around the site have been treated for emerald ash borer. The rest of our ash trees are dead or dying. Many have already been felled and burned. Although our black walnut trees were in general bigger than our ash trees at the time of property purchase, ash trees were more numerous. The loss of our ash trees is a major disruption to our landscape from which we expect it will take decades to recover. Going forward, we will work to restore and improve on the level of ecosystem integrity that we inherited. A lot of this effort will involve making sure that the space formerly occupied by ash trees, killed by an invasive insect, isn’t immediately claimed by an invasive plant, like autumn olive or common buckthorn, both present on this site and both intentionally introduced to this continent as ornamental plants.

Since the discovery of the emerald ash borer in Michigan in 2002, this pest has killed hundreds of millions of North American ash trees already and all remaining ash trees are at risk. A whole genus of trees across an area as large as a continent is threatened by one species of insect. We don’t need to write about the emerald ash borer because others have done that more thoroughly and effectively than we can. Check out to learn more about this destructive invader.

This ash tree, like the other ash trees on our site, is already a relict, a living reminder of a landscape that has moved on. While any living landscape is in a constant state of flux at some level, non-native forest pests are the only forest disturbance agents that have effectively eliminated entire tree species or genera from United States forests within decades (Lovett et al, 2016). The sudden loss of a key species like a dominant or co-dominant tree species irrevocably alters an ecosystem. One reason we have so many ash trees to lose now is because ash trees were a popular choice to replace the millions of elm trees which succumbed to Dutch elm disease in the 1970’s (Williams, 2009). Dutch elm disease was itself caused by an non-native fungus.

The implications of species loss cannot be predicted in advance because ecosystem functioning and how it interconnects to our health and our culture is so complex that accounting for all related dynamics is beyond our capability. Twenty years ago, who would have predicted that Major League Baseball players would be hoarding ash bats due to the threat posed by an iridescent beetle (Nesbitt and Rosecrans, 2022)? We already know that approximately 42 percent of threatened or endangered species are at risk due to invasive species (The National Wildlife Federation, 2022) so invasive species undoubtedly threaten many more. It is estimated that the emerald ash borer was present but undetected on this continent for over a decade. What will show up in North America in the early 2030’s?

It’s easy to look at a place and see that everything looks green and figure that the landscape is healthy. Perhaps it is. Perhaps it’s not. Biodiversity is a better indicator of ecosystem health than whether or not everything looks green. Our ecosystems were historically robust yet their vulnerability is demonstrated through seeing the ruinous impact of invasive species on system functioning. Our trees are vulnerable, too. It’s hard to see vulnerability and strength at the same time but if we see only the strength and fail to see the vulnerability, we will fail to provide the support they need. This ash tree exposes a fallacy in one of our most common conservation concepts. When a species is plentiful, we figure that the population is healthy and that it doesn’t need support or protection. When there are just a few members of a species left, we call that species endangered and try to protect it. However, by the time such protections are put in place, that species now considered endangered is likely already functionally extinct in terms of not being a major contributor to the functioning of any ecosystem. The system loss has effectively been incurred. The support comes too late. Anyone who considered ash trees endangered in 2001 would have been ridiculed.

A healthy ecosystem protects its most vulnerable members through a web of complex biological, chemical and geological interactions. Protection needs to be provided to the functioning and integrity of the system itself so that the system itself can in turn protect its vulnerable members, which it turns out is all of them.

Black Squirrel Farms strives for accuracy but everyone makes mistakes sometimes. We’re happy to update our information if needed. Please contact us if you spot an error or have a suggested edit, update or information inclusion. Help is welcome.


Lovett GM, Weiss M, Liebhold AM, Holmes TP, Leung B, Lambert KF, Orwig DA, Campbell FT, Rosenthal J, McCullough DG, Wildova R, Ayres MP, Canham CD, Foster DR, LaDeau SL, Weldy T., 2016. “Nonnative forest insects and pathogens in the United States: Impacts and policy options.” Ecol Appl. 2016 Jul;26(5):1437-1455. doi: 10.1890/15-1176. Epub 2016 May 10. PMID: 27755760; PMCID: PMC6680343.

The National Wildlife Federation, 2022. “Invasive Species”.

Nesbitt, Stephen and Rosecrans, C. Trent, 2022. “‘It’s an epic saga’: An exotic beetle, Barry Bonds, Joey Votto and the end of ash baseball bats”. The Athletic, Jan 3, 2022 issue.

Williams, Brandt, 2009. “Taking lessons from elm losses, Minneapolis prepares for ash borer”. MPRNEWS,,