An invasion biology skeptic meets an invasion biologist: A hopeful dialogue.


Setting-  Back porch in Dayton, Ohio.  Belgian Stout and a beagle mix present. 

Invasion Biologist:  “Thank you so much for coming, I hope this will be a useful exchange…Shall we begin?”

Skeptic:  “Shoot!”

Invasion Biologist: “So you are telling me there is an ash tree standing right in front of the porch?”

Skeptic: “What do you mean?  I don’t see anything but grass… a seedling?”

Invasion Biologist: “No a large ash tree!  It’s 50 feet tall with a large crown?”

Skeptic:  “This is a bad way to start a dialogue – – I have no idea what you are talking about!”

Invasion Biologist:  “There was an ash tree in my yard, 50 feet tall; it stood right there in front of us.  It died because of an infestation of the Emerald Ash Borer…a well-known exotic, invasive, insect.  As an invasion biology skeptic, are you saying that tree actually didn’t die?”

Skeptic: “Come on…”

Invasion Biologist:  “Okay, so we agree that my tree was killed by this insect?  After all the larvae were present and abundant…I chopped the wood by hand once the tree was cut, I saw them!  Can we also agree that I have lost the $1,300 that I spent to have it cut down?  That money is not actually in my wallet?”

Skeptic: “…” frowning, checks his watch.

Invasion Biologist: “I could use $1,300- the AC in my car is broken, are you sure I don’t have it.”

Skeptic: “…” scowling.

Invasion Biologist:  “Okay, so we can agree that the Emerald Ash Borer killed my tree, and also virtually every member of the genus Fraxinus across a large swath of the Midwest?”

Skeptic:  “Hmm, that is a leap- A lot things can cause a tree to die.”

Invasion Biologist:  “Yes, but these mortality rates are exponentially greater than background rates, and the causal factor is well-known, empirically, to be this particular insect”

Skeptic:  “Alright, sure, these trees are killed by the borer.  Can we get on with it?”

Invasion Biologist:  “Please just go along with me for a bit here…. We agree that the tree was killed by the borer and it’s expensive?  My tree cost $1,300.  After talking to the very person who writes the checks, I know for sure that a small park district here in Dayton is spending $250,000 just on ash removal in the next year.   They did not have that money sitting around, it cuts them deep in other areas to deal with those trees, and those are only trees that might fall outside their parks onto streets or houses, not including inside the park trees which will be dealt with in future years.  Everyone living in the region, the municipalities, the people, have trees to deal with along streets or in yards and so forth, it is *extremely* costly for the region.”

Skeptic: “Fine”

Invasion Biologist:  “Okay, so this borer is well known to have arrived in the US via cargo, probably in pallets.  This is known to be a relatively discrete event, and resulted from the insect being transported across the Atlantic Ocean in an airplane.  Fraxinus where the borer normally resides do not suffer mortality to this extent, but the ash trees here in the US have no resistance, resulting in it sweeping through our populations.  The insect was accidentally moved by airplane right into the middle of a vulnerable population.  It could not have leapt over the Atlantic on its own…”

Skeptic: “No, I am not going to agree to this, what about some kind of wind storm or other event, it surely is not impossible for them to have crossed the Atlantic. The adults can fly at least some distance.”

Invasion Biologist: “Yes they fly, but the distances are infinitesimal compared to crossing the Atlantic Ocean with no stopping spots.  We know that dispersal curves have very long tails, but this is almost beyond imagination…can we call it getting here instantaneously, without human help, “exceedingly unlikely?”

Skeptic: “Okay, fine”

Invasion Biologist: “There are a great many insects and other critters that utilize ash trees for some portion of their life cycle.  I am not sure anyone has done a comprehensive survey, but would you agree that at least dozens of insects and animals is a reasonable minimal number to assume (although the number may be very much higher)?  And, can we assume that the origin of this menagerie includes species both from local environment and those that have been transported in by humans in various ways?

Skeptic: “And some of the species that have been moved to the US, and are using ash, are causing no harm, and may in fact benefit the tree!”

Invasion Biologist: “Ohh yes!”

Skeptic: “Fine, I agree.”

Invasion Biologist:  “Okay, so the way this particular insect interacts with ash trees is VERY different from those of the existing menagerie.  Radically different.  It has swept through the range of ash, killing the tree with unbelievable effectiveness.  In some areas where it first arrived the kill rates were nearly 100%.  The genus Fraxinus, which is a very important part of both urban forests and wildlands, is in big trouble in the region.”

Skeptic:  “Okay….”

Invasion Biologist:  “The spread has been rapid, and it seems, so far, wherever the insect gets a foothold, it grows explosively.  It is penetrating into whatever insect communities exist in these habitats with ease, defeats whatever defenses the ash trees have, and establishes populations that drastically reduce the ash populations.  Tens of thousands of trees are dying in here in Dayton OH as we speak…in fact, if you don’t treat your ash tree with insecticide it can safely be assumed that it will perish in the next 5 years or so.”

Skeptic:  “I am familiar with the insect… this is terribly tedious”

Invasion Biologist:  “Humor me?”

Skeptic:  “Fine….”

Invasion Biologist:  “You’re too kind, would you like another bottle?  There….now, can we agree that the biological action of this borer is relatively unique?  That the insect is acting in a way that is different from the menagerie of organisms already here when it arrived?”

Skeptic: “mmmm, not totally comfortable with that…what do you mean unique, that’s vague?”

Invasion Biologist:  “Fair enough, but we can assume Fraxinus was doing just fine living with the menagerie, but when this one insect arrived it has experienced precipitous crashes in population, so in that way this biological action seems clearly unique”

Skeptic: “Go ahead…”

Invasion Biologist:  “Can we say about the biological action of the borer that it is characterized by: rapid population growth and spatial spread and widespread detrimental impact to a long standing member of the local biological community?”

Skeptic:  “Sounds reasonable”

Invasion Biologist:  “Can we agree that this biological action is economically important (if not, can you give me $1,300?)”

Skeptic:  Yes (and no)

Invasion Biologist:  “Can we agree that this biological action is scientifically interesting?  And that studying the reasons why this particular insect acts this way, and members of the menagerie do not, could have both scientific impact and help human society?”

Skeptic:  “Sure that sounds true.”

Invasion Biologist:  “Can we agree that there are other species that seem to exhibit a similar biological action?  Some species act this ways, and others don’t, and figuring out why is a useful goal for science”

Skeptic:  “I will go along with that”

Invasion Biologist:  Can we call this scientific study “Invasion Biology”

Skeptic:   “No:  First of all, the language is jingoistic…it suggests actual hate of all species that were not here when Daniel Boone arrived here in Ohio…

Invasion Biologist:  “… Okay how about we call this area of science: Newly Arrived Organisms With Rapid Population Growth and Spatial Spread and Widespread Detrimental Impacts to Longstanding Biological Communities… biology?”

Skeptic: “Now you’re just being a jerk.”

Invasion Biologist: “Sorry, how about we use initials:  N.A.O.W.R.P.G.S.S.W.D.I.L.S.B.C Biology?  Sounds like a good name for a journal, no?”

Skeptic: “grrrrr”

Invasion Biologist:  “Well maybe we can come up with something better…but in the meantime, we agree on every key issue!”

Skeptic:  “You want to wrap up so early…why – Do you need feed your nativist fever by reading Desert Solitaire for the 14th time and staring at some Ansel Adams photos?”

Invasion Biologist: “arrgh…!”

Skeptic: “Relax man, just kidding…but look, seriously,  you have missed the whole point: Not all “exotic” species are harmful and..”

Invasion Biologist:  “…Hold on…that is a Straw Man- you know damned well that Invasion Biologists have always taken as a central tenant that very few exotic species become invasive.”

Skeptic: “Fine, but even the concept of “native” is terribly arbitrary.”  In fact, with the planet rapidly warming the whole idea of “native” is rapidly losing meaning.”

Invasion Biologist:  “Okay…its a fair point…however, would you agree that figuring out why some **tiny fraction** of exotic species become catastrophically harmful while others just nestled down into the biotic community is a useful endeavor?  After all, this work could help us predict or mitigate negative effects, and as we established already, a few invasive species (like Emerald Ash Borer) end up being economically and ecologically devastating.”

Skeptic:  “Sure, of course, but what does “exotic” even mean at this point in history where habitats are such a mess due to human activities (eutrophication, landscape structure changes, etc.) and with the climate changing very fast.  In fact, defining “native” as some date in time, such as 1750, is completely indefensible and arbitrary”

Invasion Biologists:  “Yea, we can agree that a specific year is hard to defend; however, surely you would agree that humans moving species around the globe was influenced by the internal combustion engine, industrialization, and the eventually growth of air and sea traffic such that in modern times the probability of any particular species dispersing across the oceans, and long distances over land, has been unfathomably increased.”

Skeptic:  “Sure, but that just makes the point for me- the native vs. exotic definition is a mess in modern times!”

Invasion Biologist:  “If we agree that dispersal has massively increased due to human commerce (which we did) then picking a particular date to demarcate native vs. exotic is trivial.  The point is that species are moving around the planet in a radically different way than just 200, much less 500, years ago…which is a very short time ecologically!  These terribly Anglo-centric dates such as 1492 or 1776 do not stand up to scrutiny, and deserve your skepticism; however, the Columbian Exchange detailed by Alfred Crosby is a real Biological event and radically increased global dispersal patterns, especially post WWII, in relation to human commerce DOES stand up to scrutiny and IS biologically meaningful.  Right?”

Skeptic:  “Sure, but how can you base policy or management activities on arbitrary definitions.  You have people spraying herbicide from airplanes in order to remove species that are defined as “invasive” only because they are “exotic”, but your definition of “exotic” is weak if not arbitrary.”

Invasion Biologist:  “I am worried about herbicide being sprayed from airplanes and other spillover effects of control…very worried…however, we agreed that some of those species dispersed due to commerce will cause bizarrely massive devastation, and we agreed that the existing menagerie do not cause the same kind of damage, and we agreed that figuring out which species act that way and which do not is a useful scientific pursuit and agreed on the need for Biological research on this phenomenon.  I believe it is an *urgent* task for Invasion Biology to verify harmful effects of species that we are calling “invasive” and further to discern the ramifications for non-target species and overall ecosystem function of various control options for Invasive Species.  These are URGENT problems… within the field of Invasion Biology.

Skeptic:  “Well we agree on the urgency of these issues – so why aren’t you working on these things?!”

Invasion Biologist:  “Yes we agree…and actually, as you can see, we agree on all the issues and always have underneath the semantics.  And, I AM working on verification of negative effects, and issues related to spill-over, but continue to be mighty distracted by arguing with you!  It would be a big boost if you would help me with the difficult and *urgent* tasks ahead of us.  Could we set aside the semantics and get to work on these basic biological questions?  Will you help?”

Skeptic: …(to be continued)


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