Destructive Herbicide in the Ecosystem

Course Correction: From being “Invasives Killers” to “Biodiversity Conservationists”

 

Wake-up Call

Most of what we conservation land managers do works well and is profoundly important. But we also have to look at the parts that need fixing. Conservation land management can be wasteful, destructive, and incompetent. 

 

Both staff and volunteers want our work to be successful. On paper, it looks good for hard-working professionals to secure grant funds, have contractors work on X number of acres, and put that in a report, as if that's a sufficient measurable accomplishment. But such measures – of dollars spent, acres covered, and percent successful invasives control – leave out what’s most important. How much did the long-term integrity or health of the ecosystem improve, or deteriorate?

 

Most of us want to be positive as much as possible – especially when the challenges are so great and the resources so small. But that’s also why it’s important not to waste. The five stories below are true and more common that we wish. We need to think about how to do better. Sites aren’t identified, mostly so the facts can be presented forthrightly, without antagonizing the good people in charge, who are doing their best in most cases.

 

This post is not an “anti herbicide” protest. Wise use of herbicide in biodiversity conservation is utterly essential. Above, buckthorn, which has been re-sprouting here after every fire for decades, has been sprayed efficiently in fall, after most other species have gone dormant. The herbicide, recognized by blue dye, is clearly also damaging some desirable species. There’s often no practical way to avoid some losses. But the adjacent species will quickly fill in where the buckthorn died. It would be possible here to avoid killing any other plant, and some perfectionists feel great angst over this kind of thing. But if we followed their advice, we’d use up too much time, and a great deal of other dearly-needed work would not get done.   

 

Five Examples of Dismal Failure

 

1. Complete death of very high-quality prairie

 

A Grade A (very-high quality) mesic black-soil prairie was deteriorating from brush, mostly gray dogwood. Diverse prairie survived under the dogwood, but diminishingly. Professionals (from a contractor with a rep for taking extra care) painted the stems with the herbicide Garlon in winter. The whole prairie died in the areas where they worked. Next summer the ground was bare, except for small re-sprouts of the dogwood, which had the most vigorous root system. Despite covering a small part of the prairie, the death of a substantial patch of Grade A was a profound tragedy. 

This heartbreak baffled many experts, who evaluated after the fact. Many people assured us that they had done “this kind of thing” without the negative impact. But was it really the same? How carefully had they studied the prairie vegetation before and after? How similar was the weather? How similar were the volumes of herbicide applied? We wish we knew. Many of us are doing more experiments to learn what we can. Fortunately, in a way, few people need to worry about impacts on Grade A prairie, because there’s so little of it. Unfortunately, saving Grade A areas is a highest priority. Do we have insufficient knowledge to do it right? 

Dense stems had been cut and painted in a different, poorer quality area nearby. In that area too, the prairie died, as shown below. 

On the upper left, the dogwood was not cut or herbicided. 

On the lower right it was. But the remnant prairie died. 

For more detail on this incident, click here. 

2. High-Quality Woodland Loses Diversity from repeated Reed-Canary Mistakes

 

A rich woodland had patches of invasive reed-canary grass here and there. Contractors seem to have recognized the quality of the intermixed herb vegetation and carefully sprayed only that invasive grass. Instead of a grass-specific herbicide, they used Round-up, an herbicide that kills most plants. While they eliminated the reed-canary in the centers of the patches, they failed to spray the reed canary at the perimeter of the patches, which was hidden beneath the quality vegetation. Perhaps they were unable to see it underneath the good plants, as they worked quickly to spray the many patches in the contract area. But the result was that the dead zones where the Round-up had killed the remnant vegetation grew larger and larger over the years. 

A better approach is to carefully and assertively spray the reed canary at the leading edge of the infestation, even at the cost of collateral damage, in order to eliminate the patch once and for all. The staff people in charge said they hadn’t had enough time for more detailed monitoring. It was as bad a loss as if those areas had been plowed … or had a Burger King built on them. We have to do better. 

 

3. Foliar Spray in Good Quality Woodland Kills All – Even the Old Oaks

 

Here’s another case when the supervisors were stumped. How could this happen? 

 

In an oak woods of hundreds of acres, the volunteer stewards made slow progress on invasive brush. Contractors were hired to help out and demonstrate effectiveness on two acres. They cut adult buckthorns and sprayed the dense seedlings. On paper, for the short term, the results looked excellent. Dense patches of seedling and sapling buckthorns were entirely dead. You could walk around the distinct edge of the two sprayed acres and see a sharp line between where buckthorn in the treatment area was brown and dead – and the adjacent area was green with young buckthorn. But by the end of the summer, all the trees had died too. Some were old bur and white oaks, many feet in circumference. 

 

I asked questions about it but didn’t want to push too hard, so as to maintain a good relationship with the owning agency. Staff explained, “Perhaps they put a brush pile in the wrong area.” Clearly they hadn’t looked carefully – or even paid much attention to what happened.

 

A year later, I asked the contractor if they ever figured out what the problem had been. The fellow was surprised by the question. Staff had never asked them about it, and the contractor hadn’t been back to check. He claimed not to know what herbicide his company had used. People clearly hoped the problem would just go away. (See Endnotes 1 and 2 for some expert opinion on what had happened).  

 

At that point, I wondered if I’d made a mistake by not saying more at the time. I’d worried about provoking a backlash that might have had negative impacts on that agency’s overall program. But we need to understand this stuff. And by “we” – I mean to include volunteer stewards and advocates, who can be more willing to say that ‘the Emperor has no clothes’ when needed. Especially at this stage of knowledge, just leaving the evaluations to  overworked staff is not good enough. 

 

4. White-fringed Orchid vs. Canada Thistle

 

The Federal-endangered prairie white-fringed orchid (Platanthera leucophaea) can grow in very high-quality grasslands and sometimes in degraded ones – but very few of them grow anywhere. Last year’s census by the U.S. Fish & Wildlife Service found only 223 plants. It’s a truly rare species.

 

One degraded prairie had scores to hundreds of them blooming every year. Then, saw-tooth sunflower over-ran parts of the orchid’s habitat and mostly eliminated it. We scythed the sunflower for a few years – hoping that this treatment would help quality vegetation recover. Gradually, the orchids returned in good numbers, and other quality vegetation like smooth phlox and yellow stargrass increased. Another problem – the invasive alien, Canada thistle, was a minor presence. A contractor working in a nearby area sprayed it, despite being  asked not to do. Thinking that they knew better, they sprayed it, rather aggressively, with Round-up. The recovering prairie was badly set back. Many aggressive species began shading out the more conservative ones. In recent years, other aggressive species dominated, and few orchids bloomed there.  

 

5. Mighty Mowers followed by Massive Broadcast Spray

There are ferocious machines that can mow mature buckthorn and other brush and turn it into inches-deep “slash.” Top-killed brush resprouts the following spring, and broadcast spraying can control it. This approach can be very helpful for restoring large areas under some conditions.

Dense buckthorn can be controlled by mighty machines followed by heavy herbiciding (as shown above) or by “basal-barking” (as in Dismal Failure example 1.) 

 

What happens in oak woodlands that retained areas of remnant biota? We’ve seen this treatment wipe it out, including endangered species, and very probably much of the symbiotic soil biota as well. 

 

Perhaps a standard practice in such areas should be to set aside some of the best remnant patches for more discriminating approaches. Then the biota of these areas could spread through the rest of the woodland over time. 

 

Comparing Two Approaches 

 

Consider crown vetch, an invasive that can wipe out large areas of good prairie or savanna:

 

Approach 1. We know sites where people have been spraying “the same” crown vetch for decades. It just doesn’t go away. They complain loudly and cynically, but it’s their own fault. 

 

Their strategy? They go after the worst areas first, where they can kill the most with the least effort. Their work becomes endless whack-a-mole.

 

Approach 2. We know sites where crown vetch control was successful. That is, it’s now gone. What was the difference? 

 

The successful folks start with the smaller patches in the highest quality areas and eliminate them. They GPS or mark them on the ground and return every summer for a few years to give the final spritzing to any re-sprouts or seedlings. They search diligently around the former patch edges, as that’s where the vetch will most likely be holding on. In higher-quality areas they use one of the newer herbicides that are somewhat selective about which types of plants they control. Bit by bit, as time and resources permit, they go after the bigger patches in the poorer quality areas until those too are gone. 

 

Who’s In Charge Here?

 

All the concerns implied above are potential problems whether staff, volunteers, or contractors are doing the work. When, instead of a contractor, a staff person does the work, the person who evaluates results is typically that staff person. Given levels of resources, perhaps there’s no alternative. Most academic research doesn’t help with these questions. We need more practical, applied, insightful research by people who understand this field. 

 

At some sites, expert volunteers do the most sensitive and demanding work – often taking more delicate care than it would be possible to pay contractors to do, given current budgets. Some volunteer stewards take time to study the results of extra-detailed care and write up results. At some sites staff do excellent studies and learn from each other. Perhaps there should be some sort of clearinghouse where we all could record what we’ve learned, especially as it concerns the varied approaches that work best according to different soils, ecosystem qualities, weather conditions, etc.? And some knowledgeable editor could make the info easily accessible to practical on-the-ground folks.  

 

There are also broader problems that need discussion, study, and more-detailed best management practices. Remnants and all higher-quality areas need different practices and types of oversight than badly degraded sites. Perhaps a new profession is needed, sort of a “general practice doctor” for the ecosystem, who can recognize needs and recommend expert practitioners. That person wouldn’t mostly do the work but instead would evaluate, prescribe, review, and revise. People with such expertise would likely come from the ranks of on-the-ground restoration practitioners with extensive experience.    

Is killing invasives our goal? Or restoring integrity and health to the ecosystem? Herbicides are needed. But herbicide treatments may solve one problem while ultimately not helping, or even making things worse. Restoration requires a wise overall plan with appropriate sequencing. The work then needs close oversight by someone who has a good working knowledge of the site’s ecology and the long-range impact of possible treatments.

There are too few people capable of providing expert supervision and review. We’re not learning as fast as we could. Contractors (some dedicated and competent, some not) are often hired on the basis of the lowest bid, and no one has time to carefully evaluate the results. Or someone checks only whether target plants died – with little attention to negative impacts. The highest concern in remnants should be for the remnant species.

 

Endnotes

 

Endnote 1. Imazapyr

Dan Carter wrote: Do you know what herbicide they used? This is a common error made with an herbicide called Imazapyr. Milwaukee County Parks staff killed a bunch of trees at Wehr Nature Center by spraying lesser celandine with it. 

 

Endnote 2. What happened to those old oaks?

Another peer reviewer wrote: Since the buckthorn seedlings were densely packed, the same thing may have happened as with the dogwood clones above: too much highly concentrated herbicide migrating in soil directly or with the help of underground fungus, killing oaks by the root.  Herbicide labels have a “maximum use rate” given in amount of herbicide product applied per acre per year.  That is not the same as the maximum rate to control a given weed, which is stated elsewhere in the label.  Max use rates may be related to such failures as this one.  Or did root grafting occur between oaks & buckthorn?  As Dan Carter has said, the decision to use basal bark or foliar when desirable vegetation is present above or below ground is rarely a good idea.  Basal bark may work in such situations with a meticulous applicator & flawless technique, but such people are so rare it doesn’t warrant recommending that practice in general.

 

Acknowledgements

Thanks for helpful suggestions from Dan Carter, Christos Economou, Eriko Kojima, and two anonymous reviewers. This post also benefitted from written exchanges among Don Osmond, Dennis Nyberg, Dan Carter, and others as found here and here: