I appreciate that this question was asked now by an undergraduate. It is always good to hear good questions from young people.
However, it is a question that comes up on here periodically, and this example of a native "invasive" is always given, sometimes by me, sometimes by others. But now I wonder about the example. It may be that rather than being an example of a native invasive, it simply illustrates, very clearly, why some object to this terminology altogether. Eastern red cedar (_Juniperus virginianus_) is native to the central plains of the U.S. For Matt Chew, let me say that by saying it is native there, I mean that it was present before Europeans arrived on the scene. In much of the prairie portion of eastern red cedar range it formerly was confined to riparian areas, canyons, and steep ridges that were not subject to periodic burning. The plant is very susceptible to fire. Over time with settlement it has become more common and more widespread, moving out onto formerly treeless prairie, where it has now formed extensive thick woodlands where little else grows. These dense forested areas are often referred to as "cedar breaks." Those who object to the use of the term "invasive" for any organisms point out that those that are so described either previously had not had a chance to interact in the system where they are considered invasive (exotics) or conditions have changed such that their former absence or rarity is becoming or has becoming commonness (either exotics or natives). Some would say they have been "released" from former suppression due to conditions, as when a rare understory plant becomes abundant in the succession that takes place after a canopy is removed. The point of this is that habitat alteration is frequently responsible for "invasion," and eastern red cedar is an example of what happens when the habitat is changed in favor of a species formerly rare in a given setting. Fire was formerly common in the prairies where red cedar now "invades." The plant would have been common there all along without that single physical limiting factor. Should it be called "invasive"? Let the prairie burn again, and eastern red cedar would become a prairie rarity except in fire protected locales again. But some are finding that the restricted seasons and conditions of controlled burns fail to turn back this "invasion." BTW, a major contributor to the sudden surge of this invasion in the late 20th century is the increasing density of settlement of exurban areas by people. The land is cut up into smaller parcels and people live on them. Where people live, prairie wildfire is often considered highly undesirable, due to lives and property endangerment. David McNeely ---- Steve Young <[email protected]> wrote: > Interesting question, can a native become invasive? I would suggest that in > some instances this is the case. For example, eastern redcedar in the Central > Prairie is native, but has now become invasive in many locations. The main > reason is the lack of fire that used to occur naturally prior to settlement > by Europeans. > > For those who want to know more, we will be addressing this topic at the > NAIPSC later in June. I expect the discussion will be quite good. Maybe I'll > post a summary to ECOLOG then. > > Steve > > ___________________ > Stephen L. Young, PhD > Weed Ecologist > University of Nebraska-Lincoln > > > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[email protected]] On Behalf Of ling huang > Sent: Sunday, April 22, 2012 8:37 PM > To: [email protected] > Subject: Re: [ECOLOG-L] Invasion, or progression? > > Hi > > I am a chemist and not an ecologist but I'm very interested in this thread > since I enjoy the wetlands area close to Sacramento near the Davis Yolo > Causeway. I wondered and am interested in this invasive or progression type > question. I saw that there was a species called Purple Loosestrife (Lythrum > salicaria) that was introduced in the 1800s (?) and is a wetland flower that > has invaded wetlands. I suppose my question is how far do we go back to > determine if a species is invasive. Is there a time or case when an invasive > becomes a native? I did see this interesting online article where the > question asked was "Can native species become invasive?" > > http://ipmsouth.com/2010/11/23/can-native-species-become-invasive/ > > Thanks. Ling > > Ling Huang > Sacramento City College > > > --- On Sun, 4/22/12, Amanda Newsom <[email protected]> wrote: > > From: Amanda Newsom <[email protected]> > Subject: Re: [ECOLOG-L] Invasion, or progression? > To: [email protected] > Date: Sunday, April 22, 2012, 3:40 PM > > Very intelligent members of the public have asked me this question when they > approach me in the field and I have some time to chat. It's a great > question, because invasions biology is attacked politically on this front, so > it's one to which professionals really must craft a coherent response in > friendly conversation. > > Another point to consider is the evolutionary history of native vs. > introduced (non-native) species in any particular system. One of the reasons > non-natives are of concern is that they do not share evolutionary history > with the native community, and this contributes to the unpredictable > biodiversity loss cited by other comments presented here. > This can also be discussed in light of the homogenization of life on earth, > because there are many species favored, facilitated, or directly cultivated > by humans that are now distributed worldwide. Some of these species threaten > regional biodiversity (Check out the book Ecological Imperialism for a really > interesting perspective on colonialism as an ecological process via > introduction of new dominant species). There's a lot coming out now on > evolution and invasive species as well that is, at least in part, reasonably > accessible to a general audience or the academic in ecology/evolution who is > wanting to step into invasion biology. > > Related to this (somewhat tangentially) is that the buildup of introduced and > invasive species in systems like San Francisco Bay has also increased the > number and complexity of biological interactions, both introduced-introduced > and introduced-native. Increasing professional interest in > introduced-introduced interactions hasn't yet yielded a whole lot of > generalized hypotheses, but it has opened new windows to how complex this > issue is biologically and how best to protect species of interest as well as > local biodiversity. > > That was a far longer and more convoluted comment than I originally > intended! Hopefully, Joshua, some of that is useful perspective. Thanks for > posing the question to ECOLOG! It can be intimidating to put something like > this out there as an undergrad, and I'm glad you took the initiative. > It comes up a lot, as you can see, and ECOLOG is a great forum for this > discussion. > A. > > On Sun, Apr 22, 2012 at 9:19 AM, Ruhl, Nathan <[email protected]> wrote: > > > I posed a very similar question to a group of graduate students and > > professors during a theoretical ecology seminar a few years ago. The > > central premise was that humans, by virtue of our > > innate-desire/ability to alter our surroundings, have caused a general > > decline in biodiversity globally. That is,humans are the primary > > vector for a loss of global biodiversity, not the > > "non-native"/"invasive" species. The question was, is reduction of > > biodiversity bad or is it simply evolution in favor of species better > > adapted to live in a human-altered landscape? > > > > After much debate, the consensus was more or less that we don't know > > what all the ecological implications of a rapid global reduction in > > biodiversity will be and, because we have only one habitable planet > > currently, it would be a good idea not to break it. Therefore, in the > > absence of a rigorous ecological understanding that we may never > > actually achieve, humans should be taking steps to promote the > > conservation of biodiversity whenever possible. > > > > N Ruhl > > Ohio University > > ________________________________________ > > > > On Sun, Apr 22, 2012 at 10:01 AM, Joshua Wilson > > <[email protected]>wrote: > > > > > Good morning, > > > > > > I know that invasive and non-native species have been getting a > > > great > > deal > > > of attention lately, and justly. I understand the basic ecological > > impacts > > > and concerns invasive species cause, and the disruption of the > > > native system. My main question is: > > > > > > Why are invasive species considered a nuisance, instead of > > > adaptation, progression, or perhaps ecosystem evolution? > > > > > > Yes, human beings have been a main cause of the large majority of > > > these invasions. But even so, I feel we are part of the natural > > > system. If an invasive species exhibits more plasticity or is more > > > competitive and adaptive than the present species in an ecosystem, > > > does that necessarily imply catastrophic impacts? There are > > > multiple arguments against this, I know, many of them strong and > > > verified. I am not an advocate of invasive species dominated > > > ecosystems, but am just curious why this change and > > shift > > > is considered so extremely detrimental. I feel that stable and > > progressive > > > change and adaptation is the basis of a strong ecological system. > > > > > > I would welcome any thoughts on this, or perhaps to start a discussion. > > I > > > am still an undergrad, so my question may seem farfetched and > > > ridiculous > > to > > > some. Even so, just something to ponder on a lovely Sunday morning. > > > > > > Have a good day all, > > > > > > Josh Wilson > > > > > > > > > > > -- > > Gary D. Grossman, PhD > > > > Professor of Animal Ecology > > Warnell School of Forestry & Natural Resources University of Georgia > > Athens, GA, USA 30602 > > > > http://grossman.myweb.uga.edu/ <http://www.arches.uga.edu/%7Egrossman> > > > > Board of Editors - Animal Biodiversity and Conservation Editorial > > Board - Freshwater Biology Editorial Board - Ecology Freshwater Fish > > > > > > -- > Amanda Newsom > Graduate Student > Bodega Marine Laboratory > > ``Life shrinks or expands according to one's courage'' -- Anais Nin -- David McNeely
