Sunday, February 26, 2012

A Quiet Pestilence

If you love wild spaces and wilderness and scenic vistas of true Colorado wildflowers, as well as the diverse wildlife dependent on them, be assured that these will all soon be gone if we continue to allow weeds to spread. And we have allowed it; too often, we have participated in it! Whether our involvement with weeds is deliberate or inadvertent, we have a happy effect on them. Exotic weeds, when they are present, send a strong message that our ecosystems are not healthy. When they take over completely, they tell us that the situation is terminal. For example, the Office of Technology Assessment reported that by the year 2000, most plants in our national parks will be exotics.

The battle against exotic weeds needs to be joined before the problem becomes obvious, because by the time most of us become aware of weeds, it will be too late. If that sounds too extreme, know that we are losing this battle in increments of time and space—4,600 acres each day; 2,600 square miles of public lands (more than two Jefferson Counties worth) lost here in the West for each year we delay. At that rate, how long before there is nothing of wild America left? Yet the biggest difficulty is impressing people that this is important.

As we seem to have more experience with fire each year here on the Front Range, we also encounter more weeds, and the situations are similar. Like wildfire, exotics can completely destroy the vegetation in an area. Unlike wildfire, from which the land quickly recovers, weed damage is often permanent. Weeds strike an ecosystem like fire in dry tinder. The earth may not look scorched, may even be covered with green leafy plants with attractive flowers, but it is in many ways sterile nonetheless. Nature sometimes helps us put out wildfires but never seems to help put out exotic plant infestations. Sometimes fire improves an ecosystem; weeds never do. Unlike wildfire, however, we haven’t learned to fear weeds enough.

Because of their origin and their spread, some weeds, like the common yellow mullein (Verbascum thapsus), are nicknamed white man's footsteps. The racial reference is justified here, because, like the white man, most noxious weeds come from Europe; like the white man, they have penetrated remote parts of our countryside. A friend who sometimes gives tours to visiting Europeans reports that the one plant they always recognize, even if they are not botanists, is that mullein. Another friend, conducting a survey along Denver’s South Platte corridor, was thrilled to find broom snakeweed (Gutierrezia sarothrae). A weed for sure, but at least a native one, it was the only native plant he’d seen all day. Talk about scorched earth: Is this the future of all our special places?

White man’s footsteps. It’s an arresting image that becomes sinister when you see mullein growing alone on a slag heap, or thriving along your favorite trail. Speaking of trails, the more we build, the more inviting entrances we make into our wilder places. Weeds will find them easily, because we and our animals will bring them along.

If it sounds like we are dealing with a dreaded disease like cancer or AIDS, that image works equally well. And the cure is similar too: prevention, early detection, and eradication. But that requires vigilance, education, and cooperation. It is easiest—and cheapest—to control weeds when they first appear in an area. Most new weeds have been here 30 years and occupied 10,000 acres before they’re even reported. But you can’t report weeds if you don’t know the weeds from the wildflowers. You can’t control weeds in your backyard if your neighbor is maintaining a seed source next door.

The spread of weeds has been compared to an explosion in slow motion. BLM, for example, has 8.5 million acres of land already infested, and estimates that by 2000, 19 million acres will have been lost if weed management efforts are not dramatically increased. BLM now allocates 60% of its weed budget to biological control, which only slows the spread—those critters can’t survive if they eliminate their food source! So, biological control, some experts say, is what you do when it’s too late. Biological control requires infestation—it won’t work when there are only a few weeds in an area. It is expensive, but it is still a necessary part of our weaponry.

On the other hand, there’s chemotherapy, the last resort. Is the cure worse than the disease? Chemophobic environmentalists, of which I am usually one, need to realize how desperate some weed situations are. No one goes out looking for chemotherapy, but we can’t afford to dismiss any effective weapon. In fact, exotic invasions are the second leading cause of today’s declining biodiversity; they are costing us the animals and plants we enjoy most. In fact, nothing can eliminate our native ecosystems as quickly and permanently as exotic infestations. One ecologist, who leads his class to a special spot for field trips, says that where 60 native plants were blooming in springs past, only two can be found now. Exotic weeds discovered his location, and the spot became educational in a whole new way.

War, wildfire, disease, alien invasions—the weed message necessarily comes to us by way of harsh words and images. Let’s listen before it’s too late.

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Originally published in Upbeat, September 1996. Illustration by Jan Ratcliffe. All rights reserved. (Clearly the statistics need updating!)

More on mullein: A New Plant Community (mine) and Favourite Old Weed (by a fellow blogger).

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