Hypotheses or Myths?

Wrestling with questions about Aliens, Fire, Ecosystem Quality, and Restraint 

How do we heal nature? In the 1970s and 80s - when I learned ecosystem restoration and biodiversity conservation - the work was based on what we might then have reasonably called hypotheses. Some of these same ideas in their current forms, where they survive, would today have to be called myths. 

This work was young then. We sought to establish sound principles for biodiversity conservation. I learned much - some right and some wrong - from founders of this discipline. (See Endnote 1.)
 
Principles and hypotheses were passed largely by word of mouth. Healing nature was (and still is) young. But we had to start somewhere, so experts proposed the following hypotheses, and we tested them. 
 
After years of testing, some ecosystem managers discarded or revised those hypotheses. Some clung to them, perhaps expecting that the trial periods needed to be longer. Below, each one is treated twice. First, there's a quick summary of the thinking. Then we consider strengths and weaknesses in more detail. 
 

Hypotheses – Summarized

 
Hypothesis 1: Aliens hurt the ecosystem and should be removed to the extent possible. 
Most of the landscape today is dominated by Eurasian species, from dandelions and daisies to Hungarian brome grass and buckthorn. To make way for restoration of rare native species, we need first to get rid of the aliens.         

In a photo three decades earlier, this area was dense orchard grass, wild carrot, and other aliens. We did not pull or herbicide these “weeds.” We planted rare prairie seed and burned. The ecosystem did the rest by itself. 

 
Hypothesis 2. Whatever fire does is good - and will often be good enough.
Another way to state this hypothesis was “Let the fire decide!” If fires kill some shrub or tree species, then their loss by definition is natural. If some trees and shrubs resist fires, then their presence there is natural. Decision makers, myself included, often said “we don’t need to decide how many individual trees to retain on an acre of restored savanna or woodland.” Indeed, making such decisions would be arrogant … would be “playing God.” No – we would let the fire decide. 
 
Hypothesis 3: High-quality ecosystems resist and choke out invasive species. They’re “tight.”
I remember being assured repeatedly by some of my most respected mentors that dense conservative communities would squeeze out any invasives. A paper I was encouraged to read at the time said that apparently the southern oak forest was not a fully evolved ecosystem – the indicator being that various alien shrubs could invade and degrade it. We did fight invasives in degraded buffers, but we weren’t as concerned about a few sprigs of sweet clover or crown vetch in the high-quality prairie. 
 
Hypothesis 4. It’s best to do the least.
The remnant ecosystems need to manage themselves as much as possible. Don’t move seed around; let it move by itself. Don’t bring in seed from outside the preserve. In the case of original prairies degraded by long fire-suppression, expect many rare species that had seemed missing to reappear and bloom after a few years. The best strategy is to remove aliens, burn, and wait for recovery.
 

Ways in which all these Hypotheses turned out to be Wrong

 
The discussions below are my personal observations. If anyone knows authoritative studies or articles that handle these questions better, please send a note or make a comment.
 
Hypothesis 1: Aliens hurt the ecosystem and should be removed to the extent possible. 
 
We were slow realizing that there’s a big difference between “aliens” and what are now generally called “invasives” – although they might better be called “malignants” – as many of them didn’t “invade” but instead are just species that, under some conditions, go out of control – like cancer cells. 
 
Instead, we should say, "We will control species that are destroying biodiversity."

Species may behave differently in different soils, latitudes, etc. But where my colleagues and I work in northern Illinois, we gradually found that many aliens have minimal impact and largely fade out over time. Ox-eye daisy and bluegrasses are common in high-quality prairies, but trivial. The daisies hardly bloom, surviving mostly as a few leaves near the ground. The bluegrasses are just thin wisps here and there. Getting rid of them might be possible. But most of us have higher priorities. 
 
Invasive or malignant species are not like those typical non-native species. They are destructive killers. Teasel or crown vetch can wipe out most other species. No one knows why. Perhaps we will in time. But we know that certain herbicides will kill them while not much impacting most other species, so we eliminate them vigorously, not because they’re “alien” but because they’re deadly.
 
Many aliens are regular components now of many fine prairies, savannas, and woodlands. They seem to do little harm. They may “invade” – but they’re not malignant, so most managers ignore them. 
 
In contrast, some “native” species do great harm to remnant biodiversity in the absence of a natural fire regime. Maples and basswoods can be “native malignants” in the oak woods. As early as 1959, John Curtis wrote of maples at a Wisconsin site: “the shade cast by their canopy of saplings and young trees was sufficiently dark to wipe out the typical oak groundlayer of shrubs and light-demanding herbs … destroying the oak community as they grow, much as a cancer destroys its host.” At another site, he described the process as: “The original stand was dominated by white and black oak with an island of red oak containing a few maples and basswoods. Due to complete fire protection afforded the stand in the last 50 years, the mesic trees began to spread out, basswood going first and farthest, followed by an almost solid wall of young sugar maples … As the period of exposure to low light lengthened, the oak plants gradually died out altogether, although some persisted for decades in a weak, entirely vegetative condition.”        

In the photo above, native maples are well on their way to destroying an ancient white oak woods. The ground is a solid carpet of maple seedlings. The thousands of thin pole trees that make most of the shade here are maple with a few native basswoods and native black cherries. But gone, in this dense shade, are the hundreds of species of grasses and wildflowers and most of the thousands of species of oak woods animals, fungi, other soil biota, etc. (After restoration, Somme Prairie Grove now has more than 490 native vascular plant species.)

 
For maples to shade out most species was viewed by Curtis as “normal” succession. Following similar thinking today, in most former mesic or wet-mesic oak savannas and woodlands, all that's healthy from the ecosystem is old oaks; most remnant plant and animal biodiversity is flickering out along with the soil biota that depended on them. People are reluctant to cut the species (e.g. maples, basswoods, and hop hornbeams) that are contributing the most to the shade – because they’re “native” to the region.
 
Managers who’ve abandoned the “alien = bad” myth have a better chance of focusing on the right actions to save biodiversity.  

Hypothesis 1 – proposed revision: "Invasive" (or "malignant") species (some of which are alien and some native) hurt the ecosystem and should be removed to the extent possible. Most aliens, however, are of trivial importance. Don’t worry about them. 

  

Hypothesis 2. Whatever fire does is good - and will often be good enough.
 
Fire is a necessary, almost miraculous, healer …  in tallgrass prairies, savannas, woodlands, and most wetlands. But it’s not enough. 
 
It took longer to disprove Hypothesis 2 – because the changes take a long time, and the losses are slower to reveal themselves. We have seen fine savannas lose their species and quality because we were convinced that whatever the fires were doing must be right. We waited. Ecosystem experiments often take decades.
 
One classic prairie example was the more than three decades of annual burning of Gensburg-Markham Prairie by Dr. Robert F. Betz. The hypothesis and hope were that it would substantially eliminate the brush, at some point. The best areas of Gensburg seemed to be among our largest, purest, high-quality prairies as they recovered over those three decades. Betz was passionate about conserving prairie plants – and prairie invertebrates too. To take over management of the site as he aged, Betz hired Ron Panzer (later Dr. Ron Panzer) and encouraged him to focus on leafhoppers, butterflies, and other key insects. Dr. Panzer found Gensburg to be the richest of the many sites he studied for insect biodiversity. He also found that most prairie insects fared fine on burned areas, but a few seemed seriously threatened by fire. So he cut back the burning sharply at Gensburg. 
 
To the amazement of many of us, the pesky shrubs (that should have declined to insignificance) then exploded! Annual fire had suppressed their size. But the rascals recovered fast enough that they could suppress much of the prairie vegetation within a few years. The area we once pilgrimaged to as “the best” is now largely a shrub thicket. Lower-quality areas of the Markham prairie now are subject to regular herbiciding to control shrubs. 
 
Studies tell us that frequent burning is essential. According to a major Chicago Wilderness study by Marlin Bowles of the Morton Arboretum, the only parts of Chicago-region grasslands that maintained their quality were the parts burned at least once every two years. Thus, burning half a fine prairie every year is the minimum that would suffice. Though less studied, experience seems to show and data may reveal that frequent burning is critical for savannas and oak woodlands too. 
 
On the other hand, at Somme Prairie Grove we burned all that would burn on the average of once every two years. That is, we usually burned half every year. That schedule was not enough to control crown vetch and teasel. But it was enough to stop most oak reproduction. The classic savanna is suspected by many to have had conditions for oak reproduction only every fifty or 100 years or so. But oak reproduction was needed now at Somme because previous owners had removed the oaks over large areas. The herbs and animals in these areas were struggling to “recover full savanna biodiversity” but could not in the absence of occasional trees. So we caged some trees to stop the deer from eating them, and we raked and backfired around them to keep the fires from burning them off. When many of them have finally gotten a bit bigger, we expect to stop the mollycoddling and let fires decide which ones will develop fire-resistant trunks and which will be re-sprout shrubs. Like nature, we hope. 
 
We have to decide these things. We can’t entirely avoid making decisions. Thus, for us, “letting the fire decide” is a part of good management. But so are teasel control, deer exclusion cages, and backfires around young oaks in some cases. 

Hypothesis 2 – proposed revision: Controlled burns are a critical component of good management. But many other components are needed.”

 

Hypothesis 3: High-quality ecosystems resist and choke out invasive species. They’re “tight.”
 
It turned out to be true that high-quality sites resisted ‘invasives’ and ‘malignants’ better than degraded areas. We saw many apparent examples of this principle working out. With frequent burns, a long list of ‘pest’ species just faded away. 
 
But by the time we woke up, reed canary grass, teasel, crown vetch and others (like big maples in oak woods) were increasingly damaging the finest remnants. The infections were actually more challenging in these cases because many managers were reluctant to use herbicides that might kill quality species. Some sites degraded unconscionably, sometimes from “native” shrubs, before we discarded this hypothesis.  
 
Wise managers now treat malignant species in high-quality areas first, with herbicide if needed, and move on the surroundings when they can. Oak woodland biodiversity is increasingly seen as requiring the culling of “native” maples and red oaks. As bur-oak-related biota is the most light-dependent, invading pole white oaks may be cut or girdled there. We make decisions increasingly based on biodiversity conservation rather than on purported principles of “naturalness.” 
 

Hypothesis 3 – proposed revision: Some high-quality ecosystems resist some invasive species. But often there is no alternative to intervention - like chemical control or thinning “native” trees.
 

Hypothesis 4. It’s best to do the least.
 
It was a thrilling experiment to treat remnants as sacrosanct and watch health recover and species emerge (some species perhaps having survived only as a few leaves each year, keeping the roots alive, and waiting for fire and release from unnatural competition and shade). These places are precious and deserve permanent good care. 
 
It turned out that (understandably, for a time) excess caution repeatedly meant allowing degradation to proceed. The worst damage done by ”trusting to nature” came when we began focusing on more degraded and larger areas (all of which were badly degraded compared with the best little remnants). For example, in Somme Prairie and the Somme Prairie Grove remnants – we only slowly woke up to real losses because of this hesitancy. (There’ll be more on this in a future blog post.) 
 
On the other hand, the stewards did dispense with the fanciful seed bank myth at Somme Prairie. (Here I have to admit that the decision was over my foolish original objection.) The INAI had recognized 2 acres as Grade A in this 70-acre site. (In reality, a two-acre area had all the Grade A, but perhaps half of those two acres were dense brush with little underneath.) The original approved management plan, in our purity, said that no seeds would be brought in from the outside. At one point, steward Laurel Ross and Nature Preserves field rep Steve Byers decided that the local prairie seed being gathered each year by the North Branch Restoration Project was appropriate here. Those surviving 2 acres had had no surviving white or purple prairie clover, no Leiberg’s panic grass, and none of quite a few other standard prairie species that certainly would have originally been in those 70 acres. 
 
The “seed bank” is a distinct part of the “Do the least!” myth. It probably developed because people saw species miraculously reappear when long-neglected prairies were burned. But those species may have been surviving as roots and a few leaves, rather than as long-lived seeds. We have tested this theory over and over at many sites. There is little effective seed bank in upland prairie, savanna, and woodland communities. (There is said to be an effective seed bank in some wetland communities.) After years of hopeful burning, missing conservative species often finally return only after seed is brought in from nearby. Especially in large degraded sites, it’s high time to recognize that diverse species restoration (by collecting and broadcasting seed) should be a regular strategy for some sites.  

 
Hypothesis 4 – proposed revision: “Doing the least” is a reasonable strategy for some sites, but the overall strategy for most sites should be to do whatever will best protect and restore full biodiversity. Much initiative and effort are typically needed.

  

Thanks for reading and thinking about these questions. Please comment or send me a note if you can help with the thinking, technical details, or the history generally. 

Endnote 1.

I claim above to have "learned much, some right and some wrong, from founders of this discipline." Were we the founders of a discipline? The Illinois Natural Areas Inventory was finished in 1977. When Bill Jordan initiated the journal "Restoration and Management Notes" (now "Ecological Restoration") in 1981, there was no established discipline of ecosystem restoration. The publication was inspired by the prairie restoration at the University of Wisconsin Arboretum, launched in the 1940s by such greats as Aldo Leopold, John Curtis, and Theodore Sperry. But it was primitive indeed. The plants were planted in one-yard-square patches (or was it one-meter-square, to make it more scientific?) - one species to a patch - because intensive weeding was thought to be needed - and they didn't think they could tell the prairie seedlings from the weeds if there was more than one desirable species per patch.   

The first "how to" that I know of is "The Prairie Propagation Handbook" by Harold Rock, a naturalist at the Wehr Botanic Garden in Milwaukee. It was published in 1981 and was also inspired by the U. of W. work. I learned many details from Rock's book, but I started my restoration work in 1977. I reference no texts or experts in my early notes. I suppose I may have come across copies of the Proceedings of the North American Prairie Conference, which had been held (roughly every two years) since 1968. There was not much "how to" in them. The only mentor I remember before Dr. Robert Betz started advising us in 1978 was the Morton Arboretum's generous Ray Schulenberg. At the Arb, he had planted what's now known as "the Schulenberg Prairie" one plant at a time, but he knew how to tell those plants from weeds, and he weeded, under the hot sun. Many "new restoration experimenters" subsequently tried many new approaches. 

Restoration & Management Notes brought together the ideas of such people and was the midwife for this emerging discipline. The work was often primitive. For the first issue in 1983, Prof. Donald B. Lawrence of the University of Minnesota contributed an article entitled "Shredded Newspaper Helps Burn Green Grassland." I too (as a volunteer with the North Branch Prairie Project) contributed an article and in 1988 pulled together the initial board for the much needed Society of Ecological Restoration. 

The Natural Areas Journal was founded for the Natural Areas Association in 1981, but as the years rolled on, these professional folks seemed to inhabit a different world from the more eclectic Restoration & Management Notes folks. I wrote an invited piece for the Natural Areas Journal in 1989, recommending that these two disciplines work together - which article had no effect that I could discern at that time. (See below.)  

Whatever I've learned, I do not claim to be an overall expert in restoration technique or biodiversity conservation generally. What I sometimes seem able to contribute is more in the realm of the entrepreneur - recognizing needs and initiating or promoting solutions, that other people then improve. 

This post seems important to me in 2021 for many reasons. One example: I recently helped initiate the new Friends of Illinois Nature Preserves, which seemed urgently needed. Working with experts on many preserves, we have found "myths" like those described above to sometimes impede needed changes and work. 

Bonus blast-from-the-past: a Natural Areas Journal article from 1989:

PERSPECTIVE 

RESTORING NATURAL AREAS 

by Steve Packard

Debates rage about how big preserves need to be. Most of the sites I work on in Illinois are 5 acres, or 2 acres, or 1. They're all we have left. Or so I once thought, but ideas have been changing.

On first reading Dan Janzen's words about the dry tropical forest, I was struck by parallels to what some of us have been thinking and doing in the tallgrass prairie region. The main difference may merely be that in Illinois we've not yet learned to speak so boldly about what we know. As Janzen stated in Science,

"The increasingly vigorous efforts to protect some of the relatively intact portions of tropical nature come too late and too slow for well over half of the tropics - especially the half best suited to agriculture and animal husbandry. Its relatively intact habitats are gone. Its remaining wildlands are hardly more than scattered biotic debris. The only feasible next step is conservation of biodiversity by using the living biotic debris and inocula from nearby intact areas to restore habitats. If this step is not taken quickly, natural and anthropogenic perturbations will extinguish more of the habitat remnants, small population fragments, and the living dead - the organisms that are living out their physiological life spans, but are no longer members of persistent populations." 

In 1986 the Illinois Nature Conservancy began to acquire hundreds of acres consisting mostly of pasture, cropland, and alien scrub near Dixon. The action puzzled some, but it had been carefully thought out. Biologists from The Nature Conservancy, universities, and the Department of Conservation selected this site as a priority "large Grade C." Populations of endangered plant and bird species survived here and there along with scraps of high-quality dry gravel prairie on hilltops and some rich pockets of stream-side wetlands (the fragments, as Janzen might point out, least suited to agriculture). These were interspersed in old pasture with some native species, beat-up former savanna, and corn and soybeans. 

Rather than keeping all our ecological eggs in the basket of small unchanging preserves, The Nature Conservancy decided to protect at least one Illinois grassland large enough for animals and ecological processes. After studying its invertebrates, Dr. Ron Panzer of Northeastern Illinois University told us that, because of its large size, the preserve we now call Nachusa Grasslands has one of the richest assemblages of grassland insects he's seen, but many of the rare species exist in perilously low numbers. If over the centuries we are to retain the biotic richness that survives on this preserve, we will have to restore the landscape that surrounds the small, high-quality fragments. Seeking to plant back biodiversity on the farmland between the gravel hills and the marsh, we've had to scour the surrounding countryside for "biotic debris," the seeds of mesic prairie and savanna species that no longer survive within our current preserve of 610 acres. In the old pasture we scattered seeds of conservative species for "successional facilitation." Our techniques were developed by volunteers and professionals during more than a decade of experimental restoration management of small degraded prairies and savannas near Chicago. On the cornland we are plowing, disking, and starting from scratch. For the high-quality fragments, we remove invasives and nurture the health of what’s already there. 

Even so, eyebrows may rise on the foreheads of some Natural Areas Journal readers at the unholy mixing of base restoration with the purity of natural area management But what is the alternative? Is it better in all such cases to employ expensive manipulations to maintain tiny endangered populations on artificial life-support systems? Would we not prefer, in at least some cases where it's practical, to restore habitats that allow populations to expand into internal viability. 

And what of the tallgrass savanna, the most critically endangered of the original major communities of the Midwest? The Illinois Natural Areas Inventory found only pathetic fragments totaling 11.2 acres in the entire state. Yet there are thousands of acres of "Grade C" land that might recover with restoration management. Much of the biotic diversity of the tallgrass savannas probably survives today only in these damaged landscapes. Our choice is either we kiss this major community goodbye or we learn to restore it to health. All the vascular plant species of the original savannas seem to survive here and there. Most birds will return when the habitat does. We know much less about the original invertebrates, fungi, and soil bacteria, and almost nothing about the restoration and recovery potential of such organisms. 

But we can learn about such things, if we try. Natural area managers will have to learn restoration if we are going to have any savannas at all. Buying and restoring buffer lands and extensive "Grade C," best-of-their-kind communities is a substantial challenge to our budgets and our thinking – yet the job will become increasingly difficult as the scraps of ancient ecosystems vanish, as pasture goes to cropland, as cropland loses its fence-rows and railroad-edge refuges, and as the more conservative species gradually lose genetic alleles and populations while too-small fragments deteriorate. 

And what we learn in the process of such efforts may also be crucial to our core preserves, as we deal with acid rain, global warming, and the like. Coming choices will not be easy ones. As put by Jerry Franklin of the University of Washington (Science, Nov. 18, 1988), "Those of us who are into 'the natural' are not going to like what we will have to do, which is damage control to minimize the amount of loss. We will have to become ecological engineers, managing natural areas." We will learn management that restores ecological health because we must. We will find it increasingly necessary to look beyond the pristine core of a preserve to cope with the surrounding landscape with its physical and social infrastructure. And through this process we may also find the need and the means to participate in the larger social process of coping with environmental degradation generally. 

The dry tropical forest and the midwestem grasslands have something in common. Their futures are entwined with, and dependent upon, the economies and cultures that these ecosystems produced. The survival of these bits of nature requires that we develop new ideas. We need to explore, research, debate, experiment, and to develop clear goals, technologies, and standards. There's no time to waste. Generations that follow us will not have the opportunity. 

Steve Packard 

Steve Packard is Illinois Director of Science and Stewardship with The Nature Conservancy. 

Volume 9(2), 1989 
Natural Areas Journal (Only slightly edited in 2021)

Restoration. A discipline or a science? The drab cover (below) launched the (exciting to a few of us) new journal that, in turn, launched a discipline (and eventually a science?). Inside (but not on the cover) is the launch date: Winter 1983.

The journal cover below reflects the organization that grew from Restoration & Management Notes, which convened and named itself in 1988: the Society of Ecological Restoration (SER).  It now has two journals, the more practical and applied "Ecological Restoration" (the current name of the original "Restoration and Management Notes") and the more academic "Restoration Ecology." SER is now active in 85 countries on six continents. For reasons of policy and education it has produced regional and global conferences, 18 guidance reports, 28 books, and international standards and certifications. Ecological Restoration is affiliated with SER and published by the University of Wisconsin. The cover of its current issue reflects its energy and diversity. Lofty policies and boards are important. But key results are local, on the ground, and in the hearts of people:

Acknowledgements

Thanks for helpful comments and suggestions on this post from Rebecca Hartz, Mark Kluge, Matt Evans, Eriko Kojima, (more to come, I hope, as this draft improves ... I hope).