Best way to estimate invasive plant removal costs? Get out and dig

Plants are made for travel. They may not stand up and walk, but many plants produce seeds or other pieces that can be carried long distances by wind or animals and begin to grow. While this may be great news for the plant, such shoots can disrupt natural ecosystems and are expensive to remove.

But how expensive?

According to University of Illinois agricultural ecologist Adam Davis, a lot cost estimate to clean up junk, invasive plants they are simply estimates extrapolated by desk analysis from relatively sparse data. Not content with that, Davis suffered through hornet attacks and years of hard work to get the real dollars and cents involved in removing escaped miscanthus plants.

“For the past couple of years I have spent a week in late September digging three feet down to extract the rhizomes of Miscanthus giganteus. poison ivy, and be abandoned by this crazy group of black bald hornets. It was kind of a dangerous study, and frankly, it’s still not completely eradicated,” says Davis, professor and head of the Illinois Department of Crop Science and senior author of a recent study at Invasive Plant Science and Management.

Land managers and plant ecologists everywhere can communicate.

Davis and his research team intentionally planted controlled infestations of Miscanthus giganteus and Miscanthus sinensis in six floodplain sites and old fields across Illinois to mimic potential escapes from bioenergy plantations and orchards. When it came time to harvest, they tracked what they spent on herbicides, equipment, travel and labor hours: from $85 to $3,316 per plot.

This range reflects differences between locations, species, and the net resistance of some individual plants.

“Sinensis and floodplain forest plants died quite easily from the herbicide alone, partly because miscanthus don’t like wet feet. So these plants helpfully died. But giganteus is not. His rhizomes were so deep that we got decent results. above-ground kills, but the survivors just kept coming back and coming back and coming back,” Davis says.

Carolyn Lowery, assistant professor at Penn State and lead author of the study, adds, “Gigantaeus was harder to kill, but at least it stayed put. Whereas in the case of sinensis, we found several plants across the road where they had diverged.”

After all, this is a problem with viable seeds. Unlike Miscanthus sinensis, Miscanthus giganteus is touted for its non-invasive qualities due to seed sterility, although Lowry points to examples of viable giganteus seeds in the article.

In any case, by spraying, cutting, hacking and agonizing over seven years of remediation, the team calculated remediation costs ranging from $85 to $547 for floodplains and $390 to $3,316 for old fields.

“I’m not an economist, but I was able to put together the costs associated with everything that Adam and his team did over those seven years,” Lowry says. “Of course, usually this work is not done by heads of departments. So I reached out to several invasive plant extermination companies for an hourly rate.

“At the end of the day, we probably underestimated the on-site costs because we planted these plants ourselves and knew exactly where they were. People usually have to spend much more time searching invasive species“, she adds.

After receiving a series of real-world numbers related to the destruction of miscanthus, Lowry zoomed in with a database called EDDMaps, which tracks the location of invasive species across the United States. At the time of the study, Miscanthus sinensis was reported in 1,347 locations, mostly in the eastern half of the country. Applying the range of on-site costs to all 1,347 incidents, Lowry obtained a mean estimate of $22 million—and a range of $10 to $37 million—for the destruction of escaped miscanthus.

“A lot of the studies that talk about the costs of culling are estimated using surveys, but there haven’t been a lot of studies that have actually done the work of culling a population and used that data,” Lowry says.

Currently, miscanthus is not being expanded for bioenergy plantations as promised a decade ago. But the potential for invasion remains strong, given that the genus is still actively marketed through the horticultural industry. In addition, Davis notes that with increasing fossil fuel costs, bioenergy may become more attractive again in the not-too-distant future.

If that happens, Davies offers this advice: “If you’re planning to plant a non-native species as part of your business model, you might want to think about how much it will cost to get rid of them eventually. Just try to make some estimates on the best numbers you have. Think through the process eradication per square meter. How long would it take you to destroy that square meter and then scale it up and see if that cost is acceptable to you.”