Monoculture Blues

Yellow Sweet Clover at the Birds in Flight sculpture.

There can be a certain satisfaction in orderly monocultures: swaths of neatly-trimmed turfgrass unbroken by flower or weed, or neat rows of corn or soybeans growing in precise lines. Their efficient lines, however, belie the extremely high maintenance required to suppress nature’s natural diversity.

Iowa agriculture at work

Our row crops require huge amounts of inputs to grow and thrive in what remains of our state’s rich soil, nutrients and pesticides that may be applied in excessive amounts and run off into our waterways with disastrous effects downriver. Our neat yards do the same.

 In contrast, nature promotes diversity. A sun-loving plant may grow tall, providing shade in which a smaller shade-tolerant plant may grow. One plant may thrive in this patch, while nearby slightly different conditions–more wind that sucks moisture from a plant’s leaves quickly, or more sandy soil that drains faster, or perhaps a cooler low-lying spot that stays moist even in the hot days of summer–may be more suited to a different plant.

Disease, fire, or drought may rage through an area, but the diversity of life makes it more likely that some of those many different species and individuals may make it through the disaster than if it were, say, a community of identical elm trees lining suburban streets.

So you would think that nature, left to her own devices, would default to diversity, right? Well, not necessarily. For one thing, we humans have so manipulated the world around us that, having changed the character of what had been rich habitats harboring diverse species, it is now no longer suited to the species that evolved here.

Instead, we have made a world where scrappy generalists–like humans ourselves–are able to take over and crowd out those original inhabitants who, while perfectly suited to the world in which they evolved, are now faced with a very different world. A world where topsoil has been scraped and hauled away, leaving just a heavy clay soil. Or where we stripped the prairie of its original inhabitants, planted crops for decades and left the used up, depleted land to whatever was willing to give it a go.

Humans are actively creating a world where only weeds can live and then feigning shock and outrage upon finding so many.”

― Hope Jahren

Into these waste areas–the gravel lots, the mowed edges, the constructed habitats like the Greenway–come those scrappy generalists: the Birdsfoot Trefoil and Crown Vetch, Yellow and White Sweet Clover, Wild Parsnip and Queen Annes Lace. Reed Canarygrass–Reed Canarygrass everywhere! And even some natives get in on the action, with scrubby willow trees expanding into dense thickets and Meadow Anemone spreading from a small clump to an extensive patch over the course of a few years.

Wild Parsnip along the trail

These plants aren’t content to spring up here and there among others. Nope. Where they grow, they grow, unwilling to share the space with those plants maybe a bit less assertive, or a bit slower to get started in the spring. They may not reach the monocultural proportions of carefully cultivated row crops, and some other species may manage to hang on in their midst, but the presence of these super-survivors crowds out many others that might normally thrive there.

Now that we’ve disturbed the ecological balance that arose with hundreds or thousands of species sharing those slightly different niches, what is to be done? Do we intervene and try to slow or reverse the spread of these “bad actors” along the trail, physically or chemically removing the invaders? The City, for example, has recently invested in renovation of natural areas at TTRA and Whispering Meadows to help curb undesirable plants and restore some of the native plantings that were intended. In other natural areas around the city, prescribed burns help keep woody plants in check.

Volunteers lopping woody brush along the Greenway make a small start–but a glance at the areas where work was done shows little progress yet. There are currently no interventions planned for the Reed Canarygrass or other forbs along the trail (that I know of, at least).

Or do we let nature continue to do its thing, and hope that those aggressive monocultures will eventually be reined in by some other force? After all, there is no stasis in nature. The species that are ascendent in one era are faced with constantly changing conditions; perhaps a newly introduced pest will target some of these nonnatives, or the nutrient runoff fueling some of the excessive growth from surrounding agricultural fields will cease.

As we continue to remodel our world in a way that reduces the diversity and complexity that is allowed to thrive, we must commit to protecting and promoting those species and the habitats that support them, in every corner that we allow to escape development.

Crown Vetch creeping along a slope.