Ecological Ring-Around-the-Rosy: When Invasives Aren’t All Bad

I am trying to kill the fig buttercup
the way I’m supposed to according
to the government website,
but right now there’s a bee on it.
-Ada Limón

I can suffer the blackberries their existence in September, when they provide me with pie. My work to remove them all, which will never be complete, picks back up in October once the berries have all been eaten by human or bird, fallen to the ground in a purple splat so dark it’s nearly black, or begun to petrify still on the vine. This work continues through the darkest and rainiest months, but stops again in March. Through the summer I attempt only to hold any ground I’ve gained.

The vines of a Himalayan blackberry bush, my least favorite rubus, live for two or three years and can grow to be as thick as my thumb. When they die back, new ones grow in their place, but the old ones remain — dead, dry and brown, but entangled and still sharp. Over time a veritable thicket forms, impenetrable to a human, but not bad at all as a nesting site for songbirds, who use it like they might a brush pile or stand of native rubus or other woody shrub. This is why removal efforts halt in March, as birdsong largely absent in the preceding months, begins to make its return. The risk of destroying a nest is too high — what good would an invasive-free piece of land be, if there were no birds?

Carpenter bees, one of the most widespread native bees in the United States, are also known to nest in the previous season’s brush: a female will hollow out the woody vines and lay an egg inside, leaving behind enough pollen and resources for the larvae to feed on once it hatches. She’ll then close up the hole with plant matter and move on. This is too subtle for me. No matter how I pride myself on noticing, on seeing the world around me, I’ve never seen this. But that doesn’t mean it’s not there, not worth pausing for.

So too with honey bees (themselves not native, but more on that later). A foraging honey bee will only feed on one species of flower on any given trip away from the hive, collecting nectar and pollen from hundreds of flowers on a single foraging trip, all of the same type. This, of course, is how a beekeeper can sell you honey of a specific type — if they harvest honey right after what is known as the “flow” (of nectar) of a specific type of flower, they know that all the honey they are collecting came from that flower. With Himalayan blackberries as prolific as they are in the Pacific Northwest, nudging out what might otherwise be stands of other flowering shrubs, they have become one of the primary sources of food for honey bees in the area (though they may not serve the same purpose for native pollinators, many of which are specialized and adapted along with specific native plant species, and for whom patches of invasives are therefore totally useless).

So for the birds and the bees — just as a place to start, nevermind the underground communities that may have grown used to shade or being held intact by roots — wholesale removal of large swaths of invasives can actually pose a problem in the short term, habitat and food both gone in one fell swoop. Aldo Leopold calls this conundrum, that of an ostensibly bad thing supporting a good, “ecological ring-around-the-rosy.” Managing for these complex interactions is called in modern parlance, less poetically, “conciliation biology.”

Conciliation biology suggests that as we balance the scales of a given invasive, as we measure the damages it causes along with the benefits it provides, there might be times when the scales tip toward its benefits, at least on some time scale. There are other times that we have no choice — past a certain point on the invasion curve and we must learn to live with our invaders. It’s only another manifestation of the same problem posed by Scotch Broom, wildly invasive and also holding many a roadside back from unchecked erosion.

Aldo Leopold suggests that these problems require long thought. Thankfully, “do nothing” and “tear them all out at once,” are not our only options. Choosing the right season for control activities is one option. Joan and Eileen Bradley would suggest that allowing natives to slowly regrow, and fill in cleared or thinned areas is another — if an invader is replaced by something native that fills a similar niche in the ecosystem at nearly the same rate it is removed, the loss will not be so keenly felt. Or perhaps both: the seasons of sitting back and watching, of waiting, may be just the time something native needs to begin its march.

Sources

Carroll, Scott; Conciliation biology: the eco-evolutionary management of permanently invaded biotic systems (Evolutionary Applications, 2002)

Leopold, Aldo, A Sand County Almanac (Oxford University Press Inc., 1949)

Limón, Ada, The Hurting Kind: Poems (Milkweed Editions, 2022)

OSU Extension Service, Carpenter bees are right at home in dead blackberry canes