The Eternal Cycle of Succession
When I was asked to write an article on “invasive species”, my first reaction was to sigh and roll my eyes. (Notice that I’ve already placed the term “invasive species” in quotes… sigh!)
“I’m being baited”, I thought to myself. “Someone has a political agenda and is trying to get me to make someone angry”.
My inquisitor tried to reassure me that “No!” they did NOT have such an intention, but because of my ecological perspective and my 25+ years of experience in converting ecologically degraded sites (clear cuts, agricultural fields, sand mines, etc.) into ecologically designed food-producing systems, I “might have a perspective that others might find useful.”
Regardless as to which is more true, here we are. I agreed to write this article!
“Invasive species” have been the cause of much alarm within my lifetime and have become almost universally known among folks who are conservation minded and “environmentally aware.” Images galore can be found of Kudzu “covering everything” in the south, oriental bittersweet vines “strangling the canopies” of entire forests in Connecticut, bamboo “taking over” highway medians in the mid-Atlantic states or, quite memorable to me, seeing Autumn Olive for miles and miles along highways and popping up wherever there was a patch of un-mowed pasture in central Massachusetts where I grew up. If you’re reading this article you are familiar with some kind of organism that is considered “invasive”.
“Invasive species”, we’re told, are causing untold billions of dollars in damages, are decimating native species, are plaguing private and public lands alike, are simplifying ecologies and leading us all in the direction of becoming a planet of “weeds”. Pretty soon they’ll probably join forces with the zombies and obliterate civilization as we know it.
I don’t disagree that highly competitive, rapidly colonizing, non-native plants have observable effects within the natural world around us. I don’t doubt that “invasive” non-natives like Tatarian honeysuckle (Lonicera tatarica ) have caused local extinctions of spring ephemerals in many semi-shaded woodlands. I have seen with my own eyes the damage that insects such as Gypsy Moth, the Emerald Ash Borer, and diseases such as chestnut blight (Cryphonectria parasitica) have caused within our natural world. These effects are REAL and they are changing what nature itself actually IS.
I cannot undo the pain and anger of the losses that I see all around me on a daily basis, but my ability to cope with reality is helped by an understanding that is grounded in observable reality, the study of nature: ecology. This understanding also informs my actions so that when I get up to work in this world, I can limit the number of windmills I joust. An ecological understanding frees up my time and emotional energies so that I can be more effective at what I do. (creating perennial food ecosystems on degraded lands wherever I go!) Hopefully you can find some of what I share to be helpful as well.
One of the most important ecological principles worth knowing about, is the principle of succession. Natural succession, “old field succession” and ecological succession are some other words used for it. It can be summarized simply by understanding that ALL THINGS CHANGE. Period. Always. Your opinion doesn’t matter.
When you look out your back door, the fields or forests, lawns or gardens, or even highways that you see are all somewhere within the cycles of succession. Your own garden on a daily basis begins to sprout “weeds”. These weeds can grow so fast that they rob your crops of water and nutrients, your yields suffer and you may eventually abandon the whole thing. It doesn’t end there, though… The weeds in your abandoned garden, the rank, fast growing mostly annual weeds, don’t quite take up all of the possible niches that could be colonized by life, and some other sort of plant finds a toehold. The first wave of weeds that caused you to abandon your carrots, have changed the conditions. Perhaps they have added more carbon to the soil, or perhaps they have accumulated a particular nutrient from a different soil strata than your carrots, and they have changed the original site conditions to something different. These new site conditions provide opportunities for plants other than what is currently growing there and when seeds or other plant propagules (rhizomes, roots, bulblets, etc) blow in, fall in, are brought in by animals, etc, the plant community changes.
Your garden gives way to annual weeds, the annuals and biennials give way to perennials, especially grasses. Through the years the “old field” that was once your carrot patch, gets invaded by brambles and other thorny shrubs. The raspberries and blackberry canes invading that field even look like the arching backs of sea-serpents as they loop their way into the open areas. Within this increasingly impenetrable thorny thicket you’ll see some trees beginning to raise their heads above the mess. Many of the first trees you’ll see were once fruits or nuts dropped by some squabbling jays, or stashed by a squirrel. If the local pines had a good cone crop the year you abandoned garden, you may see a pure thicket of them growing shoulder-to-shoulder and excluding other plants. Eventually the shade beneath the tree and shrub canopy becomes so great that the grasses can no longer survive.
The conditions have changed. As the trees grow in diameter and height they begin to compete with one another for water, light and nutrients. A large percentage of them begin to die along with the shrub layer which becomes more and more sparse. Your original garden is no longer recognizable. You can now walk beneath the shady canopy on a forest floor littered with leaves and needles. It has become the typical New England “forests” that you can see all around. It may live a LONG TIME!, hundreds or perhaps thousands of years. It is not staying still, however. The “young” forest of 100-year-old oaks, hickories, cherries and pines are gradually being “under grown” with shade tolerant basswood, sugar maple, hemlock and beech. Given enough time, all but the grandest of old pines or ancient oaks will be within a matrix of shade tolerant trees.
Eventually these old, large trees die and leave a gap in the canopy. Perhaps a hurricane blows through and knocks down 100 acres of this forest. In both cases, the site has been “disturbed”. A site that was a sunny vegetable garden with herbs and flowers and hummingbirds, changed through time to become an old-growth forest which then blew down in the wind and has become a sunny spot once again with exposed soil, not from a plow or roto-tiller, but where massive root systems have been pulled from the ground. Succession has been set back in ecological time to a previous phase. The land and what you see outside your door today is not a THING, but merely one scene, one phase within the timeless drama of succession. Hurricanes, ice storms, loggers, developers, fire, grazing and trampling, the plow, the rototiller and the hoe all cause ecological “disturbances” that change the site conditions providing opportunities for other species to move in.
Your site is the stage for this drama. The bedrock and the soil that it becomes, the available moisture, summer warmth and winter cold, the climate (stable or changing, it doesn’t really matter) is the context within which this play will take place. Species that will survive in a particular site or region as it ACTUALLY IS, are the actors on that stage. The changing appearance of the landscape, in fact the entire PLANET is the play itself. Shakespeare could never have written anything so complex and beautiful.
We participate in this play whether we are conscious of it or not. Plant populations and the creatures that depend upon them, change as the conditions change. Species come and species go. The piece of earth outside your door, the drama that you see today is NOT the same as it was 50 years ago. It is not the same as it was 200 years ago. It is not the same as when the Europeans first arrived, or when the First Nations first arrived, or when it was covered with ice, or when mastodons browsed in New York, or when that dinosaur first tempted Eve to eat from that particular tree. This drama has been going on for a LONG time.
What does this have to do with “invasive species”? Well, everything! let’s use Garlic Mustard as an example…
My adventures in SW Wisconsin began in 1995 when I moved to a farm property with the intention of converting it from a row-crops (corn, peas, oats, and hay… soybeans had not really invaded yet) based dairy farm into a perennial, food-producing ecosystem. I had done my research, and had learned that upon European arrival, and for at least the previous 13,000 years or so (based on archeological evidence and based on the biological legacies of surviving plant species) that this place was what could be categorized as Oak Savanna. Roughly the same “actors” are on stage here in WI as there are in the Northeast except that here less rain falls, hurricanes don’t play as much of a disturbance role, fire plays a BIGGER role, as did grazing from large herds of herbivores. If you were to imagine your carrot patch that had become an “old field” that was punctuated by oaks and hickories with a brushy understory, that is what this place had been for who knows how many millennia. Before the canopy could close and shade out the grass, a fire would come through and re-set the shrubland.
Since Oak Savanna was what it WAS, that was what I chose as my ecological model for an ecologically designed farm. I figured that the species that thrived on this site for the last zillion years, through ice ages and global warmings, had a pretty good chance of thriving here again! Instead of fighting the weeds in my carrot patch (I didn’t really mean to get on a kick with the carrots… Sorry, carrots!) I would FARM the weeds… The raspberries, and hazelnuts and plums and grapes and apples, the fungi and the chestnuts. WAIT? Chestnuts??? Yes… Chestnuts and Oaks are both members of the Fagacae family. They are cousins and have very similar site requirements.
After arranging the rows for perennials and the crop fields in such a way as to conserve and manage rainfall, I planted the species listed above. (there are a LOT more perennial edibles at New Forest Farm than just that short list. I’m just trying to keep things simple here) Through the years, abandoned farm fields of hard packed clay and corn stubble, and badly overgrazed, compacted pasture became an “early successional shrubland”, in species composition and in FACT. Thickets of shrubs and thorns didn’t invade my farm. My farm IS the invading thicket of shrubs and thorns, and sun-loving trees, etc. As this system has persisted through the years, I have done my best to manage it according to the “disturbance regime” that it would have encountered naturally, with fire, grazing and browsing. Cattle, pigs and fowl (chickens and guineas) have been the most common livestock. Although I’ve used fire, both intentionally and unintentionally, I mostly mimic the removal of grassy vegetation with an orchard mower, and the effects of the mastodon are imitated with a chainsaw, and the front-end loader of the tractor.
What has happened here through the years, is that the site has changed. First of all, the site when I arrived in 1995 had changed from the “original”. It was no longer “natural”. A corn field is NOT an Oak Savanna. My attempts at re-creating an agricultural Oak Savanna were taking place on a DIFFERENT PLANET! The atmosphere has more carbon in it than a thousand years ago, the rainfall has a different chemistry than 150 years ago. The soil was contaminated with the residues from 60 years of chemical application and plastic bags from Wal-Mart frequently fly overhead and land on the farm to plug the digestive tracts of cattle who ingest them and die (this has indeed happened here!)
Cattle and a mower are not bison, elk and fire. The species and the system still respond well however, despite the technical differences. Tiny hazelnut shrubs struggled for years within the grassy matrix, chestnuts, apples and grapes all begin to bear. As the shrubland has matured, it has changed the site. The dense, hard-packed clay has become a nice, fertile topsoil. (still clay derived and sticky when wet) The blazing hot open fields have become lightly shaded. The once aggressive grass has become somewhat tenuous, and in places sparse. Perfect conditions for garlic mustard, an INVASIVE SPECIES! Or wait… Is Garlic Mustard the invasive species or was I, moving in with my “foreign genetics”? (I grow American, Chinese, European and highly hybridized Chestnuts, American, Beaked, European and hybridized hazelnuts, Korean Stone pine, European Varieties of apples and pears, oriental medicinal plants and mushrooms, etc.)
Or was the “invasive species” the Norwegian dairy farmer who cut the trees, plowed the sod and grew corn (a non-native invasive itself, from central America) with chemicals? Maybe the invasive species were the unnecessary, non-native earthworms that came from Europe, and revered by “regenerative farmers” worldwide as some sort of sacred cow, which increased the available soil fertility out of the range for which most natives were adapted, and converted the deep, soft forest duff to a couple of leaves scattered atop layers of castings? Maybe the invasive species are the colony-nesting honeybees brought by the Europeans, which never existed in the Western Hemisphere and are not needed for the pollination of “native” plants? Maybe the invasives are the ring-necked pheasants or the brown trout, both non-native invasives that many folks like? Maybe the “invasive species” were the Native Americans who moved out of their “natural, native” ancestral homeland in Asia and Siberia who within a thousand years in North America caused the extinction of the nine species of ground sloth, two species of giraffe, the mastodons and mammoths that were here when they arrived? Maybe the “invasive species” were the plants and animals that “invaded” after the last “Big Ice” melted? Or maybe the invasive species were the mice that ate the eggs of the dinosaur that tempted Eve? The drama of succession and change has been going on for a LONG time. What IS an “invasive species” anyways? What is a “native species?” I’ll leave these discussions to others… I’ve got Garlic Mustard to deal with!
With even a beginners understanding of ecological succession and disturbance, we can more effectively play the cards that we’ve been dealt. We can ask ourselves some simple questions that can hopefully help us to figure out how to survive within the actual reality that we are in.
What are the conditions that this so-called “invasive species” enjoys? What soil mineral profile promotes their growth? Supresses it? What successional stage provides its preferred set of conditions? How can we prevent the appearance of those conditions? Can we adjust the current conditions so that the “invasive” is inhibited? What successional phase comes AFTER the phase that the invasive enjoys? What disturbances cause the “invasive” to thrive? What disturbances will “set back” the invasive? These questions and more, are the ones I ask myself BEFORE I interact with an “invasive”. Does this invasive species bother me, the production of my operation, or values that I hold dear? This last question opens up a whole can of very revealing non-native worms!
As far as we can tell, “invasive species” don’t really care what we call them. They just ARE. They live out their natural life cycle and exist under the conditions that support their growth, reproduction and spread. From their perspective, they have done nothing wrong. They are just living their lives according to their design. By living out their lives, they will change the conditions around them. They will persist as long as the conditions exist within which they thrive. This has nothing to do with whether you think they belong there or not. It has nothing to do with your mental construct called “invasion”. It matters not to the Garlic Mustard community on my farm if I think they’re “horrible”. They probably don’t even care that they might be causing the extinction of other plants. They are just being themselves. The “invasion” then, is in our mind. We have created the labels through which we now view reality. We have eaten from the forbidden tree and we view the world as “This is “good”, let’s plant more of it. This is “bad”, its invading! Lets eradicate it!” Yes, these things have been “introduced” from one place to another. Yes they sometimes have devastating effects on the local flora and fauna during the time that it takes for natural processes to kick in. How we view them and how we interact with them is up to us.
If we CHOOSE to, we can interact with them in such a manner as to limit their effects on us and local ecologies. In my opinion, using herbicide in an ecosystem is not good for ecosystem health. Perhaps “invasive” Japanese Knotweed is “not good” either. What is better? A rampant, pure-stand forming plant that really does eradicate all kinds of species in its wake, (for a period of time (unknown to us) until it changes its site conditions to those it can no longer tolerate) or the pollution from the factories that made the herbicide, contaminated groundwater from oil extraction, the wars and economic turmoil caused by petrochemical geopolitics, the cancer, the lawsuits, an altered atmosphere and endless suffering?
What your course of action is is up to YOU! If you want an “invasion” to stop, it is best to create conditions ahead of time that are not conducive to the species in question. If you don’t want Chestnut blight on your property don’t plant chestnuts. If you don’t want plum curculio don’t plant apples or stone fruit. If you don’t want black locust (or autumn olive) create shade as quickly as possible. If you don’t want a virus that spreads by close, unsanitary personal contact, then don’t cram ten million people into the same space and cut off the water supply to the sinks and toilets of those who failed to pay their water bill as is the case recently in Americas large cities. A species will only thrive when the conditions suit its growth, reproduction and spread.
If an unwanted species has already arrived at your site or is about to, DON’T WAIT to take action! It is far easier to pull the first one or two honeysuckle or buckthorn plants when you first see them than it is to eradicate ten acres of brush and have to deal with their seed sprouting for generations.
Be adaptable! When you see the first Bradford pears arriving in your field edges (or raspberries or blackberries) graft them to a preferred variety of pear and start selling grafted pear seedlings, fruit and juice. I was once hired by a winery to help them solve their issue with invasive blackberries in their vineyards. I suggested that they introduce a line of blackberry wine. They refused to “go with the flow” and within a few years dropped their organic certification in order to be able to spray the blackberries into oblivion. (My bet is that they are still fighting that war)
When you go with the new flow, be aware that new pests and diseases will invade soon thereafter! The epic drama, the game of succession is never ending. The conditions change and we’ll have to figure out how to play along. Attempting to destroy the stage to prevent a part of the show from happening is a downward spiral.
In the meantime, remember this while on your knees pulling weeds in your carrot patch. Pulling weeds to help your carrots to grow DOES INDEED help your carrots to grow! It is a choice that you are making. While pulling weeds you are on the front lines of humankind’s long history of attempting to stop succession. You will NEVER get all of the weeds out of your garden whether you’re using chemical weed control or are using certified organic methods. As soon as you cease your efforts, the invasion has won and succession runs its course. Your garden will continue to dance through time with the actors and actresses changing by the season and throughout the years, through wind and rain, and fire and ice, drought and flood. In time even all of our buildings will come down and become the substrate for the next phase of succession.
I hope there will still be some carrots growing somewhere…