Thursday, September 8, 2016

Tunnel Vision Science demonizing Earthworms again for Forest Decline

Contain those Crawlers! Invasive Earthworms in Our Forests - What's the big deal about earthworms again?

Beneficial here – detrimental there: European earthworms decrease species diversity in North America

Another study on invasive earthworms has been released and this time from the German Centre for Integrative Biodiversity Research. What's interesting is that they use the same tunnel vision narrowed focus on just one simple subject without using peripheral view of other related contributors or lack of them within the forest biodiversity. This has been done in the other studies where researchers failed to even consider the lack of other biological controls which may have been missing in those specific study areas. I've written about this previously in the two articles before where the presence of earthworm predators such as hedgehogs, moles, various birds, etc might be missing. 
I really do not need a lot of time here rehashing old news and points I made in previous posts, but some points made in the published report were puzzling. For example take this bit in their third paragraph. After explaining the myth of Ice Age extinction of earthworms in North America and how earthworms should be there period, they go on to explain their effect on the Native Plants. 
Many native plants cannot thrive under these unusual circumstances, which is why the species diversity of the forest understory is decreasing. Wherever the worm creeps, the goblin fern (Botrychium mormo), for example, has become rare. Other plants are also threatened by the earthworm invasion, such as the largeflower bellwort (Uvularia grandiflora), the Japanese Angelica Tree (Aralia elata), . . . . . "
Image: Invasive Species of sussex County, New Jersey

Japanese Angelica Tree (Aralia elata)

Image: CalFlora
Wo there, wait a minute. Back up the Biodiversity Train for a minute. Japanese Angelica Tree ???That's not even a native plant in North America. In fact it's a horrible invasive in many places back east and up north. It looks very reminiscent of the invader out west called Tree of Heaven (Ailanthus altissima) also from Asia - China to be exact. This non-native tree easily invades many native chaparral plant community & forest locations in the western USA. But this Japanese Angelica tree is like a Tree of Heaven on Steroids. Take a look at that spiny truck and branch from the CalPhoto picture to the right here. If these earthworms are harming this invader, then wouldn't that be a good thing ? This is really a case of where the researchers didn't do their homework and have all their facts straight. Perhaps it's because their from Germany. Still, I think the common name containing "Japanese" would have been an easy clue. Even a Kindergartener would have gotten that one. Past articles have mentioned that Hardwood forest regions which are mainly Sugar Maples, Oaks, etc are said to be hurting the most and in decline because of Earthworms or Night Crawlers. Funny, in the late 1960s and early 70s when I use to visit several of our famil's farms back in Northeastern Iowa each summer, there were tonnes of nightcrawlers everywhere we hunted at night for fishing the next day, Our older generation family memebers said that they had always been there. There were no understory problems back then in forests that I personally ever saw. But why now ? It has been mentioned that these earthworms are killing Sugar Maples because these maples need an understory forest floor leaf liter for germination media. Yet, take a close look at two photos they reference below. There is no mention of where the these photos were taken, except from someone named Scott L. Loss of Oklahoma and Paul Ojanen of Minnesota.

Photo by Paul Ojanen (University of Minnesota)

Zoom in Link of Green Forest Understory

Photo by Scott L. Loss (Oklahoma State University)

Zoom in Link to bare Forest Understory

I first have to question the two radically different locations taken by one guy from Oklahoma in the south and the other guy's photo presumably in Minnesota in the north. How can you make a comparison ? The forest tree and plant diversity could be completely different. Also interesting is when you click on the zoom link of the supposedly bare forest understory in the bottom photo which magnifies the situation greatly, you see that this is actually Springtime. Not Fall or Winter. There is indeed leaves and other forest liter and numerous maples seedling are popping up everywhere. It just doesn't flow with their written narrative. They also mentioned how earthworm infested forests hurt the understory plants during summer or even drought periods. But that doesn't even jive with what Todd E. Dawson, formerly an associate professor at Cornell found when researching a natural phenomena called "Hydrailic Lift & Redistribution" of water from deeply rooted Sugar Maples to other smaller plants in the forest understory. It just seems to me lately that much of science is dropping the ball in research when they practice a narrowed worldview of tunnel vision on a specific subject. Ecosystems are driven by multiple factors, not just one. Here is the Cornell study:
Cornell University: Mother Nature's Irrigators* Plants Share Water With Their Neighbors
The other thing that doesn't fit their narrative of the disappearance of Sugar Maples in many areas are that they are being replaced by another invasive, Norway Maples (Acer platanoides). Norway Maple is extremely tolerant of shade and therefore thrives and out competes wonderfully with Sugar Maple. But they don't even attempt to reference this and they should have. For example, here is a Wikepedia piece on Norway Maple's invasiveness and how it can be a major cause of depleted forest understories. 
"The roots of Norway maples grow very close to the ground surface, starving other plants of moisture. For example, lawn grass (and even weeds) will usually not grow well beneath a Norway maple, but English Ivy, with its minimal rooting needs, may thrive. In addition, the dense canopy of Norway maples can inhibit understory growth. Some have suggested Norway maples may also release chemicals to discourage undergrowth, although this is controversial. Acer platanoides has been shown to inhibit the growth of native saplings as a canopy tree or as a sapling. The Norway maple also suffers less herbivory than the sugar maple, allowing it to gain a competitive advantage against the latter species." 
Did you notice that Norway Maple is very shallow rooted and outcompetes other plants for moisture ? Do you know why ? Like other trees here in Sweden and other Scandinavian countries where I live, they are all often shallow rooted because it rains incessantly here. If there is a month or so of no rain, it is very common to see these shallow rooted trees turn brown and eventually die if they don't receive moisture quickly. The often easily tumble over n a bad windstorm. So it makes sense that because of centuries of such habitat where constant rain is the norm, these trees have developed specific epigenetic induced characteristics which allow them to succeed in there particular Scandinavian and Siberian environment. Therefore in another foreign environment, their shallow roots desperately suck up as much water as possible in their new less wet environment. They have not had as much time to engineer themselves the way Sugar Maple also has an extensive spreading root system, but has numerous sinker roots for which it can tap into deeper subsoil layers for moisture capture. In the Oklahoma photo above which shows the supposedly bare understory, you can also see grasses in the background and they explain this in the report.
Grasses also grow well in invaded forests because their fine roots can quickly absorb soil nutrients, particularly nitrogen, and can tolerate summer droughts. Moreover, earthworms eat small seeds of certain plant species and thus directly influence the composition of the forest understory.
Yes I'm sure earthworms eat seeds, but it's doubtful they'd be capable of eating a large furry spiky Maple Seed with it's wing still attached. Another article tried to explain that they eat all the microbial community, but this seems to be nonsense since worm castings are loaded with rich microbial flora. People are going to have to look at every single science report and judge them accordingly. Not everything should ever be taken as sacred gospel. These researchers are as human as anyone else and they are therefore prone to error. Although researchers often hold themselves above the average person on the street and would probably disagree with me on that. But I have the historical record of 100+ years of know it all enlightenment which has brought the Earth and it's ecosystems to it's knees, so I think I'm still safe.
Something Else of Important Note on the two Photos above - They've recycle from another article back in 2012
Back in 2012 in the Smithsonian Blog, they were blaming Earthworms for the decline in Ovenbirds. Birds from the Midwest who make nests on the ground with twigs which create an over-like structure. I've never seen Earthworms devour twigs and sticks, but that's what they say. Take a look below of the photos by Scott L. Loss again.

Images by Scott L. Loss
You can read it and decide for yourself. Take any of these sensationistic story with a grain of salt. The are not necessarily truth just because scientific researchers say so. Frankly I see the nest is built within a clump of grass which according to the other article shouldn't be in a healthy understory. Interestingly, Ovenbirds eat earthworms as part of their diet.

One last puzzling photograph from the article
(photo: Simone Cesarz)

European earthworms of the species Lumbricus terrestris

This picture above was a pazzle to me. It looked staged. Someone took a handful of earthworms and dumped them on top of some forst litter. But the idea was that the earthworms were removing the forest litter completely. I would have muched rather seen a photograph inside the forest canopy which they said had no understory plants because of earthworms, then digging a hole in this bare canopy to reveal all those earthworms. At the same time, show a photo of a hole being dug within a forest rich in understory plants and the lack of any earthworms. Does that make sense to anyone else ? 
And yet another important dilemma. Migration of all lifeforms [not just earthworms] northward because of  Climate Change
Image - University of Washington

interactive map shows where animals will move under climate change
They said the earthworms are moving northwards because of climate change. In fact scientists have said many things will move northward because of habitat disruption in the south. But there are some very important questions we should ask: Will these lifeforms be able to find their required unique foods along these routes ? And how much of that food will there actually be if those routes become, as they've projected, high traffic areas for their species? Given altitudes and weather, can they fatten up enough and hibernate safely to survive winter through their migrations ? Also, keep in mind that there are a great lack wildlife corridors for safe travel with barriers such as highways and ever present danger from hunters as well. They will need all kinds of help from conservationists and the public in general to survive in sufficient numbers for healthy breeding populations. Is there any historical precendent that tells us this will work out okay, or are we relying on small pockets of successful experimental pilot projects which have never been tested on a massive scale ? What about testing these pilot program successes on a grand scale ? Not likely.

Image - AllPESTS.ORG
Here is a great link on Moles. This is one subject I've never seen in any of these studies regarding possible absence of moles in these supposedly infested earthworm forest locations. Many gardeners mistakenly believe moles eat and kill their precious vegetables and plants. This is false, they are after grubs and especially fond of earthworms. Unfortunately there are numerous chemical and other pest control companies who are only too happy to provide a means of killing these animals. Moles are actually in decline in many areas and little is done to see the impact this may have on increased earthworm populations. This is what tunnel vision does to real scientific research. Anyway, here is the link:
I suppose what puzzled me most was the absence of any talk about lack of earthworm predators in general. Many creatures eat earthworms. Small snakes, moles, toads, numerous birds, ants, mites, centipedes, etc, etc, etc. But again, no mention of whether or not they even bothered to look for these and if absent, why ? Were any of the earthworm infested locations ever improved by the reintroduction of any of these predators ? We'll never know. Almost every negative research paper I've ever read never once addresses these major topics. Here are a couple more interesting links for reading.


  1. Since you used one of my photos, taken in Nicolet National Forest during my M.S. research on earthworm impacts in Northern Mesic Hardwood communities and am familiar with the research, I thought it best I comment and clarify incorrect statements in your post. First, you could spell Scott Loss' name correctly, and perhaps refer to his research on Earthworm impacts to ovenbirds ( His research overlapped mine as he worked in the same region and at about the same time. Next, I don't know where you accessed your source, but the reference is likely to earthworm impacts in Japan. The study your article refers to is a meta-analysis of earthworm impacts around the world. While Aralia elata is invasive here, in it's native environment it is adversely impacted by invasive earthworms. No researcher will argue that whether the cause of invasion is humans. Without them, Lumbricus terrestris, L. rubellus and all the others would be moving at a likely 5 meters a year from their origins. If you look at my picture, that is an area I tested which showed no earthworms, and you can see the richness of the understory. My two meter diameter plots there had up to 18 species. Contrast that with some of the other pictures and count the visible species. I can easily provide some photos and sheets of data that show one species, or bare soil and a bryophyte. What you fail to understand is rather normal in any field as complex and with as many interactions as forest ecology. For example, Acer saccaharum, having evolved in thick litter environments, germinates best in litter with associated fungi. The earthworms, by accelerating decomposition, eliminate the environment for the fungi and bacteria become the primary decomposers. The mean number of seedlings per acre in an earthworm invaded site drops from 1500 pre-invasion to 400. Other species are hurt also, as they are also reliant on fungal associations. As far as predators, none are numerous or successful enough to reduce earthworm impacts. There are invading terrestrial flatworms that might reduce earthworm populations, but their presence appears confined to urban areas with high use of horticultural imports.Their impacts in large forested areas are questionable.In the long term, as in geologic time, someone, from virus to evolved predator usually shows up to start eating, and earthworms will be no exception. The problem is all the other things that are happening, such as the over-populated white tail deer and their browsing our forests into a savannah. No researcher (and most managers) debates human impacts to forests. If anything, they are the people screaming the loudest that we are in great danger, that forests, like any other natural environment, are no longer "stressed", but are kicking and screaming. But before you criticize the science, you should be familiar with it. The literature on invasive earthworms is large and well established. You need to read that before you make arguments of its validity.

    1. miskwaa - " I don't know where you accessed your source, but the reference is likely to earthworm impacts in Japan. The study your article refers to is a meta-analysis of earthworm impacts around the world. While Aralia elata is invasive here, in it's native environment it is adversely impacted by invasive earthworms."

      Belwo is the link and main article in the latest to blame earthworms for the forest problem. Take note of the "TITLE" which reference NORTYH AMERICA and NOT "Japan". These German researchers listed several North American plant species with Japanese Angelica square in the middle. This was not an American study as it comes out of Leipzig, Germany. That is why I stated their mis-step in identification.

      Beneficial here – detrimental there: European earthworms decrease species diversity in North America

      miskwaa - "First, you could spell Scott Loss' name correctly"

      I remember seeing the spelling mistake under the photo and thought I had corrected that. It is spelled correctly in the other references to him. Whatever.

      Wiskwaa - "research on Earthworm impacts to ovenbirds "

      Yes I saw the link and a lot of things can be taken as coincidence along wth the usual conjecture and assumptions. There in the abstract it states in the last sentence, "Our findings provide compelling evidence that earthworm invasions may be associated with local declines of forest songbird populations."

      My problem here is there are still too many unanswered questions which were probably never considered or asked in the first place. I'm finding this same lack throughout many studies on various ecosystem functions. First we live at a time when everything is upside down. How do you researchers even fathom what ecosystem function was like many decades ago ? The Gif I posted on species northward movement is another challenge. Did the check to see if many of the Ovenbirds also moved northward ? You do realize that climate change is the result of human researchers misusing and abusing what science has discovered and manipulating it for a product through engineering and technological innovation. There are so many unknowns, even unknown unknowns. So how can a tunnel vision approach to blame one species for a plethora of disfunctions.

      I do not have more time for the moment, but I'll come back, I am probably 7 or 8 hours difference from you over there in North America. Actually I don't even know who you are behing the Avatar, so I am unaware whom I am responding to.

      Cheers, Kevin Franck


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