Alien Plants in a Altered World

Flammable Grasses and shrubs make wildfires hotter

Photo by Tim Mossholder on Unsplash

For those of us who only watch helplessly on the evening news from our living rooms, the devastating scenes from southern California are difficult to witness.

This recent firestorm in and near LA is yet another "perfect storm" of just-so conditions--the dry version of the recent torrential floods-of-a-century in western Carolina and Virginia. The worst of the worst natural and man-made conditions join forces against places and people, landscapes and lives.

As bad as the meteorological extremes were in LA, their impact was made even worse by a new source of heat and smoke in wildfires around the world: invasive grasses, shrubs and trees. This is a historical-ecological tale in the making.

As the human population has moved into grassland, chaparral and even moist temperate woodlands, fire suppression has been a knee-jerk response to even the coolest of fires. And so native understory plants accumulate and add both tinder and impediments to fire containment.

Areas disturbed to the subsoil by the razing of land for housing or commercial uses increase the chances that the seeds of non-native plants will outcompete and replace natural landscapes with carpets of combustible invaders. Many grasses are fire-adapted and come back stronger after a wildfire.

And this silent encroachment of alien tinder has been underway for some while, and we see it making climate-complicated wildfires more frequent and more intense. I had no idea.

GRASSES FUEL FIRES AROUND THE WORLD

Photo by Erwan Hesry on Unsplash

The grotesque type specimen for this deadly over-growth of flammable flora is the fires last year in Maui, Hawaii. Sugar cane and pineapple plantations there have been abandoned, and the non-natives have moved in. A quarter of the island state’s surface is now covered by invasive grasses.

How Swaths of Invasive Grass Made Maui’s Fires So Devastating

This is not a problem unique to that island. There have been and will be other fires made worse by an over-abundance of foreign plant life. Fire-friendly grasses have invaded new habitats around the world. Five species are considered among the most problematic grasses, threatening to transform entire ecosystems.

Cheatgrass, Cogon Grass, Gamba grass, Molasses grass and buffelgrass.

…humans have accelerated that process by scattering grass seeds far from their native habitats, sometimes by accident and sometimes intentionally, to feed livestock, control erosion, and decorate gardens. “The [grass] invasions in the last 100 years or so are just a radical example of a speeded-up process that’s been happening over millennia,” says Dave Richardson, an ecologist and invasive plant expert at South Africa’s Stellenbosch University. Science.org

And in other places, it is also trees that burn in today’s hotter and drier climates. This is increasingly the problem with Monterey Pines and non-native eucalyptus.

Wildfire risk is increasing everywhere, especially in the East and South. Here’s a major reason why. | Vox

And in Oklahoma on Chickasaw lands, it is invasive Eastern Red Cedar that brings both an environmental threat and an increased risk of fire—after tribal burning practices were halted:

Returning Fire to the Landscape

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ONLY YOU CAN PREVENT…

So it is important to be aware of the role that understory invasives play, both in the ecology of landscapes AND the role they might play in future fires near you. There are no SAFE refuges from fire any more than there are from rain, as we learned in the mountain flooding in the Southern Appalachians.

Come spring, I will have more to say about the horror of bush honeysuckle in the forest just out our window and on every trail we have walked since arriving here in September. I have never seen a woodland understory so dominated by a single invasive species.

And yes, they could contribute to future fires’ intensity and also (like eastern Rhododendron) make getting to a fire to contain it nearly impossible. This was a prominent thought during the Tuggles Gap fire in the summer of 2023.

“Bush honeysuckle” consists primarily of two species. And where they take over, the understory is doomed. More on this in the spring.