Trees in the Apocalypse

By Kenton Seth:

When I was a youth in a town surrounded by obvious desertification, I was steeped in that predictable and cynical environmental pessimism common in college students. I remember listening to my elders back then who said things like: “ash trees (and worse yet their clones) are over-planted and could all be wiped out by the right bugs.” Sure enough, we’re now living it—bark beetles, the emerald ash borer, and others. Wild piñons are losing so much ground (from drought-exacerbated pest onslaughts) that I can’t bring myself to plant one at a client's home. Age and reality has softened, if not crumbled, my youthful absolutism into a practical, if optimistic, attitude I call future-proof planting.

Mikl Brawner’s article, "Trees for a Changing Climate & Resilient Urban Forest," distills specific advice for the best future-proof trees for Colorado. Every day climate change throws a new curveball and recently it’s been natives suffering. I spoke with Rob Davis, City Forester for the City of Grand Junction, who had parallel recommendations of ‘Gila Monster’ Oak, Kentucky Coffeetrees, and Chinkapin Oak. He also had some philosophical things to say.

What trees live when things fall apart? “We’ll be less picky if we are desperate.” Because of how trees are produced, Rob says, changing the palette “is a very slow job“. More than just warming, climate change has meant fast weather changes. The legume family is generally a good source of long-game trees but honeylocust are over-planted, and thereby risky. Climate change can make a historically reliable tree vulnerable to a bug.

When Rob said “climate change creates new natives,” I thought about how the fossil record shows that the earth was basically a monoculture of ferns after the dinosaur-killing meteor, as though the planet had become a bulldozed vacant lot covered in kochia weeds. Lastly, Rob was practical. He espouses hydrozoning cities with delineated areas for irrigated legacy trees and other parts of town for all low-water trees. He advises not to rely on the next caretaker of your tree to be as good to it as you are. Plant a tree that is appropriate for the climate and people that follow you.

Climate change is a global phenomenon. Thomas Freeth, in his work as Head of Plant Records at Royal Botanical Gardens Kew, tracks historical changeovers in tree species at the garden. He feels that Londoners must plant for drought: the city has a remarkably small watershed and is predicted to resemble Barcelona’s climate by 2050!

In the Santa Fe, New Mexico newspaper Rebecca Moss, in her piece, “Rethinking the dreaded Siberian elm“, interviews a handful of authorities all posing the awkward question: (In the face of native-tree killing climate change)…”Do you really want to cut down something that is doing OK when other things are dying?” A biologist roommate and I were once snowed-in and decided to take a Christmas bird count. The activity changed from a wine-drunk gag to a humbling observation: after half a day, we spotted 17 species of bird, all taking refuge or forage on one big, nasty, messy Siberian elm that hung over our big nasty apartment building. This doesn’t exonerate these elms from being the new Genghis Khan, but we need to remember all factors at play. It was that day I realized the messiest trees were the best for wildlife.

If Colorado became a Mad Max hell-scape, we would all throw nativism to the wind and seek shade under Siberian elms. Natives are best but foreigners have advantages and are a long-running plan B for places and folks that can’t afford the best tree - and not all foreigners are invasive. (Note that the majority of invasives are wind- or bird-distributed, first introduced by authorities, not gardeners!). So, if natives, so dear to my heart, are not the last and only way to pick trees in the future, how will we manage assessing all the variables and risks?

We’ll need resources like like Henrik Sjöman and Arit Anderson’s book, set to come out early 2024: The Tree Selection Guide: for climate resilience, carbon storage, species diversity, and other benefits.” It not only discusses trees’ fitness to survive, but describes, measures and ranks their actual services from cleaning the air to amount of shade. It’s a brave vanguard to gather and share this sort of knowledge, which will be essential to make prescient decisions for us in a complicated future.

Going organic or going native are hard enough. These noble goals ask us to draw lines through gray zones in order to make decisions. But every new nuance we learn makes us re-draw those lines, and reality often upends our ability to stay on one side or the other. In the words of Charles Mann, who in The Wizard and the Prophet, chronicles humanity’s dualistic response to limited resources, “climate change is a wild card” that complicates prior problems we have.

To prevent massive ash tree death from sun-baking Colorado’s cities, we have to use an insecticide. Fortunately, much work has been done out East to find systemic non-neonicotinoids for this, and most decision-makers evaluate trees before saving them. To convert a patch of truly noxious weeds to a native meadow within the human constraints of codes, laws, and budgets, we may be forced to use an herbicide. In an effort to save water, The City of Denver used recycled water on parks but found a new problem: accumulating salts harm the old conifers. Finally, using appropriate native plants is a moving target when even historic natives are no longer safe with new local climates. Jacob Mares, Wyoming’s Community Forestry Coordinator, says, “Climate-ready trees have been the low-key talk for years… now (palpable climate change is) finally happening. When your zone is changing, so are the plants that grow there. Trees are on the move!”

While sometimes possible, it can be very hard to undo this massive mess we made with fossil fuels and chemicals without using either, especially when alternatives are nascent. Systemic change can’t happen overnight. So, to succeed or to transition, we are forced to compromise and to learn. We are forced to hold two (or more) truths in our minds at once and resist the temptation to deem them irreconcilable, trashing all but one.

What can we do? If we have thirsty old existing trees, they deserve to live out their service lives while we plant young replacements. We can also keep an open mind. “You gotta be ready to try new things.” says Mares. We must be not only receptive but active in observing and learning what is actually working - what trees are alive in rough conditions already? We can also be graceful. Rob says “I’m glad trees don’t judge humans for what we do…” We can temper our judgements towards our conventional neighbors, designers, professionals, municipalities, and also with ourselves. We need grace to make the paradigm shift from being a consumptive, dominating species to service-fulfilling, positive members of the ecosystem in a living, green world. Aren’t we capable of that?

Kenton J. Seth is a Western Colorado-based garden designer and plant junkie. Recognized for his crevice gardens, he also specializes in dry, native, and ecological gardening in an effort to create "future-proof" landscapes. Visit paintbrushgardens.com and kentonjseth.blogspot.com.