What is the Role of the so-called 'Invasive Species'?

This question is being explored more and more. Many claim that the role of invasive species is to destroy local biodiversity by out-competing local species. This perception is rooted in the competition paradigm. What if the invasives are helpers. A single step in a long process of ecosystem restoration?

If we can see them as a single step, a temporary phase that comes and once a certain threshold is met, leave naturally, our worry about them lessens. They become tolerable to some degree with the understanding that we can work with them to speed along the phase and move onto the next one.

The alternative, to work against them, generally results in a loop stuck on repeat. The same park or woodland is treated every decade or so to kill thick honeysuckle or some other invasive species. The site gets degraded with each chemical application. The stress diminishes ecosystem resilience and the site is reclaimed by invasive species, every time. Fortunately alot of folk are working in urban areas and removing invasives while also addressing soil health and planting natives. Overall they are a small group at the moment but we can see the wave growing.

The biodiversity used to be much greater than it is now. Not only have we lost species to extinction and currently have many on the almost extinct list, but their abundance is declined severely across the landscape. Most acres have a minor fraction of the abundance of species they had 250 years ago.

On property surveys the same few species are seen acre after acre. It's the same few species from property to property as well. These acres were once abundant with biodiversity when the indigenous were living here, before European & American settlements arrived. The great decline has already happened so blaming some relatively new player in the system is distracting and avoiding the solution. It's just filling a void in an attempt to reverse a trend.

What is the role of these invasive species that are rapidly moving into our landscape?

Here are some current thoughts...

Each is unique and so the answer is on an individual basis with some common overlap between some species. All together it is clear these so called 'Invasive species' are filling a niche to restore and regenerate ecosystem health.

There are others sharing this perception in books and articles, blogs, and their on-the-ground work, etc. etc. I began testing it and examining the ecosystems I'm working in to see if it held any truth. Time and time again I see this perception of niche roles is true. Where there are invasives there is an exhausted and usually compacted soil.

The multitude of berries being produced by the bush honeysuckle and autumn olive is nature doing it's best to feed the birds and wildlife in the absence of native berry producing species. Our woodlands and prairies were once full of native berries throughout the seasons. The honeysuckle and autumn olive are solving a problem that we humans have created and continue to create. What will the birds eat? The berries are essential for sustaining bird populations given that most of the native berry species have declined in abundance.

Have you ever tried to pull an autumn olive up with the roots included. The roots are thick, many branched, and spread in all directions out from the stem. They are breaking the soil up and adding quite a bit of organic matter mixed in to various depths. Compacted soils in fields and urban areas get tremendous benefit from autumn olive. Bush honeysuckle is similar on a smaller scale.

I see Sericea lespedeza and I see a soil healer doing it's best to mitigate soil compaction and loss of soil structure on severely degraded agriculture sites. Ample seed is being made for the rodents and birds to live on. The rodents and birds return to the site and add their contributions to restoring the vitality and health of the ecosystem.

Instead of understanding what is happening, many dose the site with toxic chemicals in order to preserve and intensify the pathway of declining soil health. All we have to do to get rid of sericea is put some shade on it. It disappears when shade arrives. Sericea requires full-sun. Instead of spraying chemicals we can just let the site reforest or become shrubby. The sericea is just a step to get that soil covered over and begin restoring health. I

The answer is really quite simple for this one. Millions of dollars have been spent on research and eradication efforts of sericea and the answer is so simple. Shade. The site needs some rest. That's what the sericea is shouting loud and clear. It's holding on the thin layer of soil horizons left after the wear and tear that American settlements & economy bring to a soil.

At a recent workshop a colleague started yelling at me because he has so many acres to manage and if it weren't for chemicals the land he manages would be covered in invasive species. The property he manages is in a city. Ok, I guess yelling at me is a fair argument??? His response exposed his grief for his actions and I think that one day soon he will realize that the chemicals are a new problem only making matters worse. Killing microbiota has lots of consequences.

Multiflora rose with its large thorns is shouting stay away. There are thousands of acres of woodland in central Missouri that are covered in multiflora rose. Many are challenging to hike through because the rose is so thick. These woodlands that are covered in rose today have a history of over-grazing by livestock. The thicker the rose the greater the impact of livestock has been.

The story we tell is that the livestock didn't like to eat the thorny rose but the livestock did graze on everything else, eliminating the competitors of the rose and allowing it full access. While this story is true there is another story. The woodland is now basically saying "stay away, I need some rest." It's an effective strategy because most humans and livestock do stay away.

The rose produces highly nutritious berries as well. The roots work underground to mitigate the damage done and regenerate the soils. For ecological management we work to bring the rose into balance while tending to overall ecosystem health. Once health is restored the rose fades away on it's own. When we deal with the issue head-on we fill the niches so the invasives aren't necessary.

Cedar colonizes abandoned agricultural fields. The cedar has deep roots that mine nutrients and minerals from deep in the sub-soil and drop them on the soil surface to regenerate the depleted soils. They particularly play a well-studied role in bringing calcium up from the subsoil's and dropping their calcium laden leaves on the soil surface: one tiny step in the process of restoring soil health. The roots are doing great work to regenerate depleted soils.

The cedar produce an abundance of berries that overwinter on the trees. The evergreen foliage provides cover for many wildlife species. The cedar are basically a multi-function ecosystem fertilization/restoration treatment.

Many land managers cut the cedars so they can 'reclaim' the field and possibly plant species deemed desirable. Why not let them stick around and heal these lands? Every time I dig a soil pit in these old-field cedar thickets I see a degraded and sick soil. The topsoil is always missing.

In central Missouri we usually see oaks and other hardwoods growing up between the cedar. These hardwoods didn't return to the site until the cedar worked it's magic. On sites where the cedar is allowed to remain, the oaks grow faster in height and overtop the cedar eventually. Once over-topped the cedar are in shade and stop growing, beginning to decline and eventually perish. The cedar only remain one generation on many of these sites and then it is gone. It comes to fill a niche and then leaves. It prepares and ushers in oaks and other desirable hardwoods. It's nature's nursery for the next stand of hardwoods.

When I work in the stands with overtopped cedar, where the cedar are in decline, I look for ways to keep the cedar hanging on as long as possible. I want to retain the cedar for the benefits it still provides. It's non-competitive with the taller oaks. It's still dropping calcium and providing other soil health benefits. It's still providing some cover and food for wildlife. Cutting it down slows the ecosystem restoration process.

What do you see when you see invasive species? What is the role they are playing?

Learning their niche roles helps us come into better alignment. Work becomes more impactful and results more successful when we acknowledge these needs that the so-called 'Invasive species' are filling.

If we understand that the site needs berries to feed the birds, or soil restoration, we can work to fill those needs with native species that have been lost from the site. Now work can yield positive benefits and the species that would have treated with toxins leave the site naturally. Allow a field of sericea to reforest and the need to poison all the biology on the site is no longer needed.

Consider that we are just looking at a window in time and that these species will not be here forever. They are a transient player in the system. They are here to fill a niche that was previously filled by ___________ (the species that were lost). And/or they are simply here to to provide a service to the ecosystem and then they disappear.