On the brink of a big change, learning from the mesquite tree
Branches of the Honey Mesquite. Thomas Farley, CC0, via Wikimedia Commons
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This is going to be the last newsletter before a bit of a hiatus, don’t worry nothing is wrong but I do have news which is that I am moving to Tucson, Arizona. I know, big news. Tucson is a beautiful little desert community where I lived for about six years and where I’ve spent a lot of time here and there ever since, and it has always held a special place in my heart, wherever I’ve lived. Jamie and I have been kicking around the idea for a long time now and found a place we like and decided to go for it. So that is something I have been working at for a few weeks now, and will be working on for the next few weeks as we pack up our stuff, ship it across the country and then make our way there.
There are a handful of reasons for the move, including some family reasons, some Boston-related reasons, some Tucson-related reasons, but overall we are very excited about it. I guess in a climate and politics-related newsletter, such a relocation does raise a few questions as to how and why one moves to a hot desert climate as temperatures are rising and water becomes scarce, and also how and why one moves to a political battleground state in a time of, um, political battles. You can read some past thoughts on these topics here and here, but a lot of it has to do with the kind of place Tucson is. There’s this weird kind of resilience and camaraderie that you get among people who choose to live together in the desert, and also—in contrast to its much larger, more aggressively air-conditioned sister city Phoenix—a kind of loving co-existence with a hostile environment.
I will write more about this dynamic and also all the tensions and challenges that come with it in weeks to come, but for now I think I will offer a brief meditation on one of my favorite representatives of that harsh environment, which is the mesquite tree. Mesquite may lack the grandiosity of the saguaro or title of its cousin the palo verde, Arizona’s official tree. But more than maybe any of the many special flora of the Sonoran Desert, I’m really looking forward to spending more time among mesquite.
Part of the desert legume family, along with palo verde and ironwood, they can disappear into the background of a place like Tucson, the same way a poplar or maple might in New England, but they are anything but ordinary. One of my favorite things about them is that, although they make for great city trees, shading yards and lining streets and living through just about anything, they have this tendency to ooze a black-brown oily pitch, sometime when they are sick but usually after you trim them. It’s a defense mechanism that seals off the tree’s wound, sending a message to its human landscapers—you can put me here and admire me, appreciate my shade, but if you try to cut me back, I will bleed on your sidewalk and stain it the color of my bark. Mesquite has no respect for our concrete and asphalt. It has lived here far longer.
I learned about mesquite’s several exudates and their self-healing and even medicinal qualities from a book I read about the tree recently, Mesquite: An Arboreal Love Affair, by Gary Paul Nabhan, an Arizona ethnobiologist and nature writer. It is honestly a very strange book, full of groan-inducing (and weirdly sexual?) wordplay that I’m kind of surprised made it past an editor in the volume that it did. But it also was fascinating, and paints a picture of this gnarly emblem of desert living, one with many qualities that we can all aspire to as earthly residents, especially living through challenging times.
For one, as noted, it is an astoundingly resilient, fucker of a tree. Mesquite are practically unkillable. You can cut one down to nothing and it will grow back. They have incredible self-healing capacity, aided by the greasy sap they exude, but also a dense gum that forms and hardens into a crystalized resin over its wounds. These substances have been put to use for food and medicinal purposes over the years, as have mesquite pods, which can be ground into a sweet and cinnamon-tinged flour used in tamales and other recipes, or even mezquitatol, a mild beer once brewed by the O’odham.
Mesquite react and adapt to any number of harsh conditions. They allow longhorn beetles that chew their bark to reshape their architecture as is useful. In times of drought, they’ll allow their branches to be pruned back and regrow fewer replacements. When it’s wet, they sprout right back and grow taller than before.
Also aiding their survival is the fact that they are covered in three to four inch spikes. When they are young and vulnerable, the spikes are far denser, but the more established they are, they dial it back a bit. But don’t worry, if you cut a branch off, the spikes on the replacement branch will be denser than before, and three or four times longer. It is a tree that seeks revenge when wronged.
Storied community organizers in the desert landscape, they recruit others for protection. Mesquite and their older relative the acacia (devil’s claw or cat claw) are known to develop symbiotic relationships with species of twig ants, which fight off herbivores that threaten the host. Some ants will even trim the branches of nearby trees that might be horning in on their sunlight. One ecologist has observed that the trees can even “taste” the saliva of a threatening insect and emit a chemical that makes the friendly ants go berserk on the invader.
But they are more than tough. They are nurturers and architects of desert ecosystems. Mesquite and their relatives are “nurse plants,” allowing cactus, shrubs, and succulents to live in their shadows, protected from the intense sun and heat. More than that, they are keystone species that set into motion the growth of “resource islands” within the desert. Mesquite take root and interrupt the desert wind, allowing debris and nutrients to begin to gather at their base, which feeds the tree, but also allows other species to grow around it, and by extension invites pollinators, birds, herbivores, and up the food chain. The fungi and bacteria that serve and are served by host trees become rich underground. The resulting resource islands can have 10 times more nitrogen and other nutrients than the surrounding sand.
Eventually they may grow into mezquital or bosques, lush arboreal habitats dominated and sustained by mesquite. Mesquite-based ecosystems are some of the richest lands for native bees in the world. The Great Mesquite forest along the Santa Cruz River, which sadly no longer exists, was once so lush, home to some 85 kinds of birds, that the “avian densities, number of nests, and the size of trees inspired descriptors using magical or even spiritual terms.” (Roy Johnson and Ray Turner)
The way they create sanctuaries within harsh environments, Mesquite are masters of autopoiesis, the process by which a natural system reengineers its surroundings to create a network of parts needed to survive. Nubhan quotes scientists Fritjof Capra and Pier Luigi Luisi, who describe how a mesquite “brings forth a world.”
“That’s right: It brings forth a world, a microcosm [within] the desert that is in ways less desertlike.”
Part of the secret to its ability to pull this off comes from the fact that it establishes deep roots, settling in and drawing upon the ground where it stands, growing far more extensively than is visible to those of us above ground. One record-setting mesquite had roots estimated to reach down to a 200-foot depth, four times the height of the tallest known mesquite. Excavated trees are known to have four to five times more biomass below ground than above ground, one of the biggest such known ratios.
As I try to begin to stir the ground that has accumulated around me over the past 10-plus years, drawing up roots to find new ground to sink into, to offer shade to new allies, to hopefully add resources to a new island, and to jab predators with a thorn if necessary, I will think about what else I can learn from my friend the mesquite, appreciate its black pools left on the concrete, and hopefully eat a mesquite tamale or two.
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OK I gotta go pack so we are going to keep this one nice and tight for a change. I look forward to sending correspondence from a new home, and if we are IRL friends and this is the first you are hearing about this move, please don’t be mad I’m in a pre-move state of total disarray, it is nothing personal.
Tate