With all respect to Martin Meiss: There are classic examples of dependence between specialist species that can collapse with the extinction of one species. Perhaps you are centering your argument in temperate plants with no recorded specialists interactions I can think of a handful of species that would go extinct if a host plant or a key pollinator or seed disperser went extinct. Or perhaps insect species may have specialized on Chestnut that we will never know about because they went extinct. How many studies are there on dependence of insect species on one species of plant that cover the whole range of the plant species? My guess is there are more species indirectly or directly associated with Chestnut than papers studying the number of species associated with it.
Ecosystem collapse... yes that term is extreme but a change of state in an ecosystem is very possible. Take the current lack of beaver dams and large Salix stands from Yellowstone as an example. If there had always been wolves this would be a frequent state of the ecosystem, instead the ecosystem has changed to a even state of Moose and Aspen. (If interested read recent work by D.T. Hobbs and his lab members). According to Hobbs the state of Salix and Beaver will never get back to Yellowstone even now that the wolves are back. So yes human actions have "raped" the ecosystem and changed some of the features it has forever.. what is even more frustrating is that extirpating a species is way easier than figuring out the direct and indirect effects it has. This does not mean every single species has coevolved with others strong and unique relationships but it does mean there is a lot we do not know to claim species are spendable and will not cause a change in the ecosystem. Example of an introduction of a single species and its direct and indirect effects: COS 97-2: The impact of complete bird loss on seed dispersal and plant recruitment in Guam Haldre S. Rogers, Joshua J. Tewksbury, and Janneke Hille Ris Lambers. University of Washington Background/Question/Methods Frugivorous birds are thought to perform critical services for fleshy-fruited trees. By consuming fruit, they can move seeds away from the parent, where mortality is often high, and increase germination through pulp removal or scarification. However, there are few large-scale examples of disrupted fruit-frugivore mutualisms that demonstrate the importance of generalist birds for fleshy-fruited tree species. Our research takes advantage of the mass extirpation of forest birds from the island of Guam caused by the introduction of the Brown Treesnake (Boiga irregularis) to investigate how the loss of frugivorous birds affects plant recruitment. We measured the seed shadows for two native tree species on Guam and three nearby islands with healthy bird populations using seed rain traps placed under the canopy and at 1, 5, 10 and 20 meters from the canopy. Traps were collected monthly for one year. For the same two species, we also planted seeds handled by birds alongside seeds unhandled by birds to determine whether bird handling influences germination rates. Finally, to determine if differences in dispersal distance could be observed at the seedling stage, we measured the distance between a randomly selected seedling and its nearest conspecific adult (i.e. most likely parent) on the same four islands. Results/Conclusions Results from the seed rain traps indicate a significant shift in the dispersal kernels between Guam and nearby islands with birds; seeds fall closer to the parent tree on Guam than on islands with birds. The strength of the response varies by species, however. In our germination experiments, bird handling increased germination rates for one focal species. The effect of disperser loss is also apparent at the seedling stage, as seedlings are much closer to a conspecific adult on Guam than on islands with birds. Collectively, these results suggest that birds are important for plant recruitment of fleshy-fruited species, but also that the severity of the impact of bird loss varies by species. Since approximately 70% of tree species in the native forests of Guam have fruits dispersed by birds, the forests are likely to be significantly affected by the loss of birds. And with the possibility of large-scale avian extinction looming on many islands, and many bird populations in decline globally, understanding the consequences of frugivorous bird loss may be critical for preventing widespread changes in other forest systems. Genoveva Rodriguez-Castaneda Dept. of Ecology and Environmental Science Umeå University SE-901 87 Umeå, Sweden phone: +46-90-786 53 73 fax: +46-90-786 78 60 --- On Fri, 12/17/10, Martin Meiss <[email protected]> wrote: From: Martin Meiss <[email protected]> Subject: Re: [ECOLOG-L] Defining Biodiversity To: [email protected] Date: Friday, December 17, 2010, 2:27 PM This thread contains statements of the kind that I think get us in trouble, if not with the public, then with our scientific rigor. Axel Ringe's post begins with what looks like an inclusion from a previous post with this statement "...one metaphor for biodiversity that I remember was the phrase "web of life". The imagery contained in that phrase not only conveys the complexity (species richness)of the organisms making up an ecosystem, but can also convey the importance of the connections and dependencies among those organisms. Pluck one strand, and the whole web may collapse..." Sure, it's presented as a metaphor, but is it a good one? First of all, I have never seen a spider web collapse because on strand was plucked. Spiders are better engineers than that. Even if you *sever* a thread, it usually only causes part of the web to fold up on itself. Second, does anyone know of an ecosystem that has collapsed because one species (or some other entity) was "plucked"? Also, what does it mean to say that an ecosystem has collapsed? That all it's species are extinct? That the habitat that it once occupied is now barren and lifeless? Extreme overfishing may cause an extinction or two, and we can say that the fishery has collapsed, but that collapse is an economic phenomenon, not ecological. The chestnut plague in the early twentieth century virtually wiped out the American chestnut, a dominant species of the eastern forest canopy in many places. This caused hardship for humans who used chestnut products, but I'm not aware of any other species that died off with it. In fact, we could say that many other tree species benefited as they moved into gaps left by the chestnut. Slaughtering the American bison was, in my opinion, a terrible crime, but the vultures loved it, at least for a while. If we want a vivid metaphor to promote conservation and that will stick in the public's mind, maybe we should talk about "environmental rape." This makes the point and at also makes clear that we are talking about *human values*, not scientific truths. Now to Warren Aney's quote: "...A single-age, single-species tree plantation may be productive in economic terms but it lacks species, genetic and structural diversity so it is not as ecologically productive, stable or resilient as it could be because of this lack of biodiversity...." Yes, of course it lacks species, genetic, and structural diversity, because that's how it was defined. This is like saying an all-wood house lacks bricks. It's true, but then what? Further, since it is a plantation, it's not supposed to be "ecologically productive." It's supposed to produce whatever its owner's planted it for, presumably wood. Nor is it supposed to be stable or resilient; it's supposed to last for thirty years or so and then be harvested. Admittedly, during this time its low diversity might make it vulnerable to disease outbreaks, but this risk may be economically justified by the ease of managing a uniform stand and then clearcutting it. Why am I kvetching about these points? In the context of a list serve, I think it is fine to throw out ideas and see what people make of them. However, if these issues are not well thought out and carefully articulated before they are advanced as the basis for public policy, they will not hold up well in debate. The proponents may wind up looking bad and their cause harmed rather than helped. Martin M. Meiss 2010/12/16 Warren W. Aney <[email protected]> > As a field ecologist who has frequently evaluated and described natural > systems in their entirety and then communicated this information to > non-scientists, I find the term and concept of biodiversity very helpful. > To me, the best definition is the most general definition: biodiversity > relates to diversity of species (including genetic and age diversity) and > of > structure, currently and over time. A system with high biodiversity tends > to be more productive, stable and resilient. > > A single-age, single-species tree plantation may be productive in economic > terms but it lacks species, genetic and structural diversity so it is not > as > ecologically productive, stable or resilient as it could be because of this > lack of biodiversity. > > Warren W. Aney > Senior Wildlife Ecologist > 9403 SW 74th Ave > Tigard, OR 97223 > (503) 539-1009 > (503) 246-2605 fax > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:[email protected]] On Behalf Of Alexandre F. Souza > Sent: Thursday, 16 December, 2010 13:37 > To: [email protected] > Subject: [ECOLOG-L] Defining Biodiversity > > Hi Euan, > > I use the broad definition of biodiversity as senctioned by the US > Congressional Biodiversity Act, HR1268 (1990), according to which > > "biological diversity means the full range of variety and variability > within and among living organisms and the ecological complexes in which > they occur, and encompasses ecosystem or community diversity, species > diversity, and genetic diversity." > > I think biodiversity should continue to have a broad and > all-encompassing meaning, and the communication problem you mention > arises much more from the use of the term in place of more specific > ones, when we refer to specific issues. When communicating with the > public, we should be more specific when speaking about specific issues, > rather than abolishing a term that has a broad meaning, and that should > be reserved for broad themes. > > The California Biodiversity Council has a compilation of scientific > definitions of biodiverstiy > (http://biodiversity.ca.gov/Biodiversity/biodiv_def2.html). > > Best whishes, > > Alexandre > > Date: Mon, 13 Dec 2010 15:05:31 -0800 > From: "Ritchie, Euan" <[email protected]> > Subject: Defining biodiversity, and does the term capture the public's > attention? > > Hi everyone, > > I have just returned from the Ecological Society of Australia meeting > and a= > mong other issues, there was much discussion about the term > biodiversity. M= > any people argue that this term is hard to define, and importantly, the > pub= > lic have no idea what it actually means and therefore they have less > connec= > tion/concern to preserve/conserve species and habitats. I thought it > would = > be interesting to hear how others define biodiversity, and if this term > isn= > 't helpful for conveying the importance of species diversity to the > public,= > what term(s) should we use? > > Over to you, > > Euan > > > Dr. Euan G. Ritchie, Lecturer in Ecology, School of Life and > Environmental = > Sciences > > > Dr. Alexandre F. Souza > Programa de Pós-Graduação em Biologia: Diversidade e Manejo da Vida > Silvestre > Universidade do Vale do Rio dos Sinos (UNISINOS) > Av. UNISINOS 950 - C.P. 275, São Leopoldo 93022-000, RS - Brasil > Telefone: (051)3590-8477 ramal 1263 > Skype: alexfadigas > [email protected] > http://www.unisinos.br/laboratorios/lecopop >
