Over population

[JohnB]

You must have been editing your post as I was writing mine.

 

There is ALWAYS ecological balance between populations of any animal, including humans, and its environment over the long term though there is always oscillation around that balance point over the short term.

 

This is demonstrable scientific FACT.

 

If this were true, then there would be no extinctions. For example the sabretooth died out because it was a forest hunter and with the changing climate the forests became grasslands and it could no longer catch prey. Constantly changing regional and global climate as well as competition and evolution means that the forces on the ecology can never balance.

 

Similarly with the more recent descent into and climb out of the Little Ice Age. As the weather got colder, then northern species would have moved south and put pressure on the more "equatorial" ecologies. Even if there were originally a balance in the equatorial regions, it would have been thrown off by the incoming species. If they then arrived at a balance then it would again be thrown out as the world warmed up again.

 

Nature and ecologies are dynamic rather than static and therefore can't be in balance. Ecologies must always be changing and adapting to changed circumstances and can't be balanced.

 

Edit. We're definitely cross posting. I'll call it quits for the night and answer tomorrow night. Otherwise we'll both be editing posts all night long.

Edited July 29, 2011 by JohnB

[Greg Boyles]

You must have been editing your post as I was writing mine.

 

 

 

If this were true, then there would be no extinctions. For example the sabretooth died out because it was a forest hunter and with the changing climate the forests became grasslands and it could no longer catch prey. Constantly changing regional and global climate as well as competition and evolution means that the forces on the ecology can never balance.

 

Similarly with the more recent descent into and climb out of the Little Ice Age. As the weather got colder, then northern species would have moved south and put pressure on the more "equatorial" ecologies. Even if there were originally a balance in the equatorial regions, it would have been thrown off by the incoming species. If they then arrived at a balance then it would again be thrown out as the world warmed up again.

 

Nature and ecologies are dynamic rather than static and therefore can't be in balance. Ecologies must always be changing and adapting to changed circumstances and can't be balanced.

 

Edit. We're definitely cross posting. I'll call it quits for the night and answer tomorrow night. Otherwise we'll both be editing posts all night long.

 

Alright we are quibling over time scales here. Over the very long term all species are doomed to extinction....big deal. Over shorter time periods species remain in ecolgocial balance not withstanding external shocks (climate shifts, diseases, tsunames, exceptional rainfall) that alter the balance. After such shocks species always return to ecological balance until a shock comes along that they are unable to adapt to and become extinct.

 

We are the only species with the intelligence to recognize this and to regulate our breeding and our resources so as to avoid the boom bust cycle that all other species are subject to.

 

Should we not use that intelligence for the collective, as opposed to individual, good?

[CharonY]

Eh, this is more a evolution/ecological topic, but I have to point out that the assumption of a baseline, over which the whole ecosystem oscillates is rarely true. There are often oscillations, but the baseline tends to shift, often much more rapid than geological time scales. If you want to find something that oscillates around a stable baseline for any given time you really cherry-pick your parameters (i.e. population size, area, time frame etc.).

[Greg Boyles]

Eh, this is more a evolution/ecological topic, but I have to point out that the assumption of a baseline, over which the whole ecosystem oscillates is rarely true. There are often oscillations, but the baseline tends to shift, often much more rapid than geological time scales. If you want to find something that oscillates around a stable baseline for any given time you really cherry-pick your parameters (i.e. population size, area, time frame etc.).

 

Are you folks really going to deny the well established science of ecology where all this is demonstrable and widely accepted in order to deny that the same principals apply to the human species?????

 

We no doubt collectively think that we are smarter than nature and that her rules do not apply to us, but in the end nature will win out over our technology.

[swansont]

Are you folks really going to deny the well established science of ecology where all this is demonstrable and widely accepted in order to deny that the same principals apply to the human species?????

 

We no doubt collectively think that we are smarter than nature and that her rules do not apply to us, but in the end nature will win out over our technology.

If it's well-established, it should be no problem to give links to supporting information. Population behavior for some non-human species tends to be much more dynamic than simple oscillation about some baseline.

 

https://www.math.duke.edu/education/ccp/materials/diffeq/predprey/pred1.html

http://www.tiem.utk.edu/bioed/bealsmodules/predator-prey.html

[Greg Boyles]

If it's well-established, it should be no problem to give links to supporting information. Population behavior for some non-human species tends to be much more dynamic than simple oscillation about some baseline.

 

https://www.math.duk...prey/pred1.html

http://www.tiem.utk....dator-prey.html

 

 

OK I will paly along and assume you are just trying to get me to justify my statements and that you don't seriosuly question these scientific facts.

 

But it will have to wait till I get back.

 

The graph of lynx vs snow shoe hare in this link: https://www.math.duke.edu/education/ccp/materials/diffeq/predprey/pred1.html

shows very clearly that the populations of both species have oscillated around an average over almost 100 years and therefore in ecological balance.

 

Explosions and crashes of the hare population are closely mirrored by the lynx population.

 

Humans are one of the few species that can transfer to new food resources, or coopt food resources from distant parts of the globe, when the original one is driven to through unsustainable expansion of our population.

But this cannot continue indefinitely. Sonner or later we will run out of resources to transfer to or coopt and our population will crash too.

Edited July 30, 2011 by Greg Boyles

[JohnB]

A couple of points.

 

Firstly, and I could be misunderstanding, but the concept of "ecological balance" appears to derive from the previous "Balance of Nature" concept. These relatively static concepts were challenged by J. Wu in the 1995 paper "From Balance of Nature to Hierarchical Patch Dynamics: A Paradigm Shift in Ecology".

 

Wu argues that the static models don't accurately reflect the true population data. Interestingly he mentions Hall 1988 in the context of models and a comparison of the data to the modelled outcomes. (I hope the link works) Hall compares the models, specifically mentioning the "Lotka-Volterra Model".

 

Specific in this case is the Lynx/Hare relationship shown in the pred1 link above. This is apparently a standard in textbooks for justifying the Lotka-Volterra models. The graph in the link is adapted from Saunders 1953, but others have used the same data. Hall uses a similar graph from Smith 1980. (Figure 5 in the Hall paper)

 

He points out;

First of all, the changes in the lynx population sometimes precede those of the hare (Gilpin, 1973, incidently an ecological theorist), something that makes absolutely no mathematical sense unless hares eat lynx.

 

But the real killer is;

Second, a closer look at the original data showed quite clearly that the two sets of population data were not from the same region:

the hares were from Eastern Canada near Hudson's Bay and the lynx were from Western Canada (Finerty, 1979).

(Emphasis mine)

 

While it is obvious that both populations were cyclic, it is impossible for there to be a predator/prey relationship between the two. Therefore the graph is not supporting evidence for the idea of an "ecological balance" in the populations.

 

What I find interesting is that after a few hours on google scholar it appears the concept of "ecological balance" is something that is simply assumed as being correct, the term is used quite frequently in the literature. Hoever it appears to be something that "everyone knows" and there is little on whether it actually exists. Those papers I could find concerning the existence of "ecological balance" or "Balance of Nature" were unanimously against the concept.

 

I'm willing to be shown to be wrong, but the "balance" concept seems to be an idea that is still hanging around even after being disproven by empirical evidence. This is actually the focus of Wus 1995 paper.

[Greg Boyles]

A couple of points.

 

Firstly, and I could be misunderstanding, but the concept of "ecological balance" appears to derive from the previous "Balance of Nature" concept. These relatively static concepts were challenged by J. Wu in the 1995 paper "From Balance of Nature to Hierarchical Patch Dynamics: A Paradigm Shift in Ecology".

 

Wu argues that the static models don't accurately reflect the true population data. Interestingly he mentions Hall 1988 in the context of models and a comparison of the data to the modelled outcomes. (I hope the link works) Hall compares the models, specifically mentioning the "Lotka-Volterra Model".

 

Specific in this case is the Lynx/Hare relationship shown in the pred1 link above. This is apparently a standard in textbooks for justifying the Lotka-Volterra models. The graph in the link is adapted from Saunders 1953, but others have used the same data. Hall uses a similar graph from Smith 1980. (Figure 5 in the Hall paper)

 

He points out;

 

 

But the real killer is;

 

(Emphasis mine)

 

While it is obvious that both populations were cyclic, it is impossible for there to be a predator/prey relationship between the two. Therefore the graph is not supporting evidence for the idea of an "ecological balance" in the populations.

 

What I find interesting is that after a few hours on google scholar it appears the concept of "ecological balance" is something that is simply assumed as being correct, the term is used quite frequently in the literature. Hoever it appears to be something that "everyone knows" and there is little on whether it actually exists. Those papers I could find concerning the existence of "ecological balance" or "Balance of Nature" were unanimously against the concept.

 

I'm willing to be shown to be wrong, but the "balance" concept seems to be an idea that is still hanging around even after being disproven by empirical evidence. This is actually the focus of Wus 1995 paper.

 

 

It seems quite obvious to me that balance refers to the ration of a species and its food source.

 

In the lynx / hare relationship, the balance is in the ratio of lynx to hares. Since a lynx requires a minimum number of hares per day in order to survive and cannot migrate to another area or otherwise transfer to other resources once all the hares have gone the 'balance' is maintained one way or another.

 

If the lynx get too numerous they diminish the hare population to the point that the lynx start starving to death to eventually restore the optimum ratio. The hare population may increase and the lynx population responds by increasing to restore the optimum ration. If that does not happen then the hares eat out all their food resources and starve to death themselves, again restoring the optimum ration.

 

The precise size of both popoulations may be quite dynamic as some of you have pointed out but the ecological balance, i.e. the predator to prey ratio is mostly maintained despite the magnitude of the populations.

 

Humans are different to all other animals species in that resource scarcity, over the long term and in the global context, has not checked the expansion of our population. We simply keep transfering to other resources and consume them to exhaustion. That is why we are having such a severe impact on the global ecosystem. Sooner or later we will run out of resoruces to transfer to or we cause such severe environmental degradation, through climate change in particular, that any resources that we might transfer to will be largely destroyed.

 

So, since resource scarcity has not controlled our numbers, we must be smart and do it by reducing our own ferility on the global scale. Possibly via involuntary methods if necessary. Once again this does not mean that I advocate forced sterilisation as there may be other options open to us. The alternative is that our population will, sooner or later, crash with all the unthinkable human suffering that will be associated with it. We are fast approaching the point where will be forced to choose the lesser of evils.

Edited July 31, 2011 by Greg Boyles

[CharonY]

Greg, I think you missed the point. Due to the spatial separation there is cannot be any connection between the indicated lynx and hare population. In the review (which is really a good read and with a few hundred of citations it is also one of the central reviews in this area), the authors showed that overall empirical data is not in agreement with predictions of equilibrium models, including the study John mentioned.

The conclusion is that there is no good direct evidence of truly equilibrium systems to be found.

[Greg Boyles]

Greg, I think you missed the point. Due to the spatial separation there is cannot be any connection between the indicated lynx and hare population. In the review (which is really a good read and with a few hundred of citations it is also one of the central reviews in this area), the authors showed that overall empirical data is not in agreement with predictions of equilibrium models, including the study John mentioned.

The conclusion is that there is no good direct evidence of truly equilibrium systems to be found.

 

What ever the precise year by year details of the relationship are, the undeniable fact is that you can never have a lynx population that is equal or larger to than the hare population. Universally true for all predator prey relationships. Similarly you can never have a hare population so large that it consumes vegetation faster than it can grow.

 

So we are arguing about the nature of the equilibrium not that equilibrium exists.

 

You are arguing that there is little or no equilibrium in the absolute numbers of hares and lynx because they fluctuate quite widely. But I am arguing that there MUST be equilibrium in terms of the proportions of each animal. Without equilibrium both species would go extinct in a short space of time.

 

All animal population tend towards proportional equilibrium - it is an evolutionary inevitability. Those animals that don't remain in proportional equilibrium with their food sources become extinct. As will we if we don't start collectively using that grey matter we pride ourselves on.

 

On that graph, if you divided the number of hares by the number of lynx at each corresponding peak and trough you would propbably find that the resulting fraction remains within a fairly narrow band.

Edited August 1, 2011 by Greg Boyles

[CharonY]

The point is not the time. The problem is that the data set where collected from different areas. I.e. connections between these two populations are likely by chance, not by mechanism (in order to show that they have to be from the same region, obviously). If you look at the respective graph, you will also notice that at times the lynx increase predates the hare increase, a point also discussed in the Hall paper (have hares started hunting?). Also it was mentioned that similar cycles are also found in populations where hares alone live, further indicating that the found association was just chance.

 

Really, check those papers out. They should be worth your time.

Edited August 1, 2011 by CharonY

[JohnB]

On that graph, if you divided the number of hares by the number of lynx at each corresponding peak and trough you would propbably find that the resulting fraction remains within a fairly narrow band.

 

So all you have to do is show how the lynx numbers in Hudson Bay effect the hare numbers on the Alaskan border, some 1,500 miles away.

 

All animal population tend towards proportional equilibrium - it is an evolutionary inevitability.

 

Can you provide proof of this inevitability?

[Greg Boyles]

The point is not the time. The problem is that the data set where collected from different areas. I.e. connections between these two populations are likely by chance, not by mechanism (in order to show that they have to be from the same region, obviously). If you look at the respective graph, you will also notice that at times the lynx increase predates the hare increase, a point also discussed in the Hall paper (have hares started hunting?). Also it was mentioned that similar cycles are also found in populations where hares alone live, further indicating that the found association was just chance.

 

Really, check those papers out. They should be worth your time.

 

Ok then predator and prey populations that clearly not geographically separated such as the African savannas and any other similar habitats.

 

Surely we are not going to engage in a debate about the validity of proven demonstrable tenant of ecological theory (and basic common sense) based on one study whose data may or may not represent non-interacting or partially interacting populations of predator and prey.

 

So all you have to do is show how the lynx numbers in Hudson Bay effect the hare numbers on the Alaskan border, some 1,500 miles away.

 

 

 

Can you provide proof of this inevitability?

 

 

Look I am not going to give you lessen on basic ecology (predator prey relationships) on this forum.

 

Go and do you own background reading and then come back here and question my posts - it is basic scientific fact that you learn at secondary school biology.

Edited August 1, 2011 by Greg Boyles

[JohnB]

Greg, so far you have only been making statements;

 

There is ALWAYS ecological balance between populations of any animal, including humans, and its environment over the long term though there is always oscillation around that balance point over the short term.

 

This is demonstrable scientific FACT.

Over shorter time periods species remain in ecolgocial balance not withstanding external shocks (climate shifts, diseases, tsunames, exceptional rainfall) that alter the balance. After such shocks species always return to ecological balance until a shock comes along that they are unable to adapt to and become extinct.

Are you folks really going to deny the well established science of ecology where all this is demonstrable and widely accepted

you don't seriosuly question these scientific facts.

All animal population tend towards proportional equilibrium - it is an evolutionary inevitability.

it is basic scientific fact that you learn at secondary school biology.

 

If the facts are so widely accepted and easy to demonstrate, why haven't you done so?

 

So far only two papers have been referenced in this context, both supplied by me and both disagreeing with what you say. It's not about giving me a "basic education in ecology" it's about you providing proof to back up your assertions, and so far you have failed to do so. So could you please provide some sort of references? (preferably peer reviewed)

 

Surely we are not going to engage in a debate about the validity of proven demonstrable tenant of ecological theory

 

Then show the proof, that's all I'm asking. (BTW, the term is "tenet". The meanings are: "An opinion, doctrine, or principle held as being true by a person or especially by an organization.", "a belief, opinion, or dogma" and "a religious doctrine that is proclaimed as true without proof." )

Edited August 1, 2011 by JohnB

[Greg Boyles]

JohnB I am making statements about widely accepted ecological theory.

 

Your questioning the basic theory of predator prey coupling is as foolish as some one questioning the theory of evolution. While precise details of both are still to be filled in and finalised, the frame works of the theories are now beyond questioning.

 

All you are saying to me is that you have studied little or no biology and have a poor undersanding about the ecological concepts I am enunciating.

 

Predator-prey coupling

 

Here is one link! Satisfied?

 

I am sure that I could come up with a few tens of thousands of other reputable sources telling you the exact same thing! Both on the web and in university libraries.

 

notice that at times the lynx increase predates the hare increase, a point also discussed in the Hall paper (have hares started hunting?).

 

Big deal. We are not talking about a precise mathematical relationship here. We are talking about a complex biological system with many links and therefore about curves of best mathematical fit.

 

Although hare are the main prey of lynx, did you consider that lynx are capble of preying on animals other than hares when they are plentiful enough.

 

E.G. From a movie I once saw about a biologist living in the Alaskan wilderness to study wolves .......... wolves normally prey on medium to large herbivores, but when in Alaskan tundra in spring they feed on voles which undergo a seasonal population explosion and are therefore far easier to catch.

 

Did you consider that the lynx are doing something similar and that this might account for the increase in lynx numbers predating the increase in hare numbers? So perhaps if the graph included the numbers of all prey species, not just hares, then the anomoly in relation to the hare numbers you have pointed out would be accounted for.

 

But as with climate change, short term minor variations do not disprove the overwhelming pattern.

Edited August 1, 2011 by Greg Boyles

[JohnB]

JohnB I am making statements about widely accepted ecological theory.

 

Yes, you are. However this is the internet and why should I or anybody else take your word that this is in fact "widely accepted ecological theory"? Which is why you've been asked for proof. A chemist reading this thread has no background knowledge of biology and cannot tell whether or not your statement is correct unless you provide some evidence to back it up. This is the point that you are missing. Repeating that something is "widely accepted" means nothing without proof.

 

This started when I challenged the idea of "ecological balance" and provided arguments that it doesn't actually exist. The lynx/hare thing came up to demonstrate the predator/prey relationship but it's been shown that the two populations are so far apart that there can be no causal relationship between the two sets of numbers. I provided a peer reviewed paper that said as much. Whether the lynx might or might not eat something else as well is beside the point, the lynxes are 1,500 miles from the hares. You simply cannot use the data to support a causal predator/prey relationship.

 

When you finally provided some "proof" it was to a webpage that uses as it's first example of Predation Theory, the now known to be wrong lynx/hare data. So that part fails to make the case in favour of the concept of "ecological balance" or cyclic predation theory.

 

The second example on the page was an experiment using Paramecium and to quote from the page;

Paramecium, which also proved useful in test-tube studies of competition, was placed in culture with a predaceous protozoan. These laboratory studies found that cycles were short-lived, and the system soon collapsed.

 

So rather than finding an "ecological balance", the system collapsed. The only way to make the results match the "logic and mathematical theory" was to interfere with the system and keep adding prey. This experiment, rather than supporting your ideas directly opposes it.

 

The assumption of the page is this;

Logic and mathematical theory suggest that when prey are numerous their predators increase in numbers, reducing the prey population, which in turn causes predator number to decline. The prey population eventually recovers, starting a new cycle.

 

Yet it doesn't provide any proof at all of the actual existence of the predation cycle in nature. The lynx/hare data is bogus, the simple experiment collapsed and the complex experiment discussed later collapsed after 4 cycles.

 

Going to the "Summary" section we see again;

Mathematical models and logic suggests that a coupled system of predator and prey should cycle: predators increase when prey are abundant, prey are driven to low numbers by predation, the predators decline, and the prey recover, ad infinitum.

 

However data shows that this is not what happens and this is accepted by the comment;

Some simple systems do cycle, particularly those of the boreal forest and tundra, although this no longer seems the rule.

 

Note that no evidence is present to actually confirm the first part of this statement. The disconnect between models and reality is explained by;

In complex systems, alternative prey and multi-way interactions probably dampen simple predator-prey cycles.

 

This might be true, or it might just be an opinion. Some actual proof would be nice. Yes, I did notice where the page is from, I'm assuming it's a basic summary page for the course taught there. Unfortunately, being a summary of the course doesn't make it proof, especially when it's using flawed data to make its case.

 

I am sure that I could come up with a few tens of thousands of other reputable sources telling you the exact same thing! Both on the web and in university libraries.

 

Then would you mind finding one or two? So far all you've shown is that courses in ecology continue to use bad data 17 years after it has been shown to be bad, and that rather than finding an "ecological balance" predator/prey systems collapse. Neither of which is helping your case.

[jeskill]

Greg (Not JohnB. My apologies.)

The Lokta-Volterra model of predator-prey cycles is a fantastic model for understanding very simple relationships, hence why it is taught in BIO101. But the truth is that it is not actually a good model for describing the reality of complex ecological interactions. This is because it does not take into consideration the impact of nonlinear dynamics, which can have a profound effect on the stability of a system.

 

This is an old paper, but describes the issue from a mathematical perspective: http://www.jstor.org/stable/1935675

And here's a book on the subject: http://books.google.com/books?id=ZHoyfY5KgpcC&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

 

As for what can cause nonlinear dynamics, two examples are saturation of predators in the system and limited resources for either predators or prey even if prey is abundant (this can occur if the prey is good at hiding or defending itself).

 

Just want to edit to clarify: the predator-prey cycle is NOT a fact; it's a model used to describe ecological interactions.

Edited August 1, 2011 by jeskill

[CharonY]

Just want to edit to clarify: the predator-prey cycle is NOT a fact; it's a model used to describe ecological interactions.

 

 

This is indeed the crux of this discussion and something that Greg does not appear to accept. L-V has so far not been validated on a broad basis.

 

 

And I think this is the reason:

it is basic scientific fact that you learn at secondary school biology.

 

In secondary school "facts" are taught. The problem in teaching at university is that you have to unteach many of these facts.

 

Big deal. We are not talking about a precise mathematical relationship here. We are talking about a complex biological system with many links and therefore about curves of best mathematical fit.

This is an incredibly big deal. We are not talking about rough trends, but about direct relationship. If there is none, we just matched random patterns (and again, the linked papers discuss it in that terms). Only because it looks neat it does not mean it survives statistical scrutiny (which is what ecological model have to provide, otherwise it is just gut feeling).

Let us spin this around, if there are copious examples of it, why do text books rely on these few that have been thoroughly criticized in academic literature? Text books are good introductory reads. By their very nature they tend to make shortcuts to provide easy to understand narratives. And sometimes these narratives are wrong or incomplete.

Edited August 1, 2011 by CharonY

[jeskill]

So, since resource scarcity has not controlled our numbers, we must be smart and do it by reducing our own ferility on the global scale. Possibly via involuntary methods if necessary. Once again this does not mean that I advocate forced sterilisation as there may be other options open to us. The alternative is that our population will, sooner or later, crash with all the unthinkable human suffering that will be associated with it. We are fast approaching the point where will be forced to choose the lesser of evils.

 

This is like telling someone who's lost 20 pounds in the past year that they need to go on a diet. From a global perspective, humans have been reducing their overall fecundity for the past 20 years and the trend is continuing. Even in African countries, we're seeing a reduction in fecundity. I posted this on another thread, but look up Bongaarts et al. (2009) if you don't believe me.

 

Yes, everyone should be allowed access to contraception, but that is a social justice issue, not an environmental or ecological issue. Policy measures that are specifically formatted to limit fecundity in order to improve environmental sustainability are redundant because, as stated before, FECUNDITY IS ALREADY DECREASING. Moreover, given human life spans, it wouldn't have a measurable effect in the next 50 years anyways.

 

On another vein, when you make grand statements about the impact of the global human population on the world, you're limiting your ability to see the local patterns that affect ecological sustainability. Different ecosystems have different carrying capacities. The technology used to grow agriculture can drastically affect the carrying capacity of a specific location. There are some situationsin which a large population is actually necessary to keep an agricultural system sustainable.

 

I've said it before and I'll say it again: improving the sustainability of the world will not occur if we focus on decreasing the global population size. That's like thinking you can reduce the deficit by simply cutting programs.

[Greg Boyles]

Yes, you are. However this is the internet and why should I or anybody else take your word that this is in fact "widely accepted ecological theory"? Which is why you've been asked for proof. A chemist reading this thread has no background knowledge of biology and cannot tell whether or not your statement is correct unless you provide some evidence to back it up. This is the point that you are missing. Repeating that something is "widely accepted" means nothing without proof.

 

An areas of science that are well established and widly accepted this becomes just silly. The onus is not on me to provide proof but on you to do the background reading and therefore ask sensible and worth while questions.

 

This started when I challenged the idea of "ecological balance" and provided arguments that it doesn't actually exist. The lynx/hare thing came up to demonstrate the predator/prey relationship but it's been shown that the two populations are so far apart that there can be no causal relationship between the two sets of numbers. I provided a peer reviewed paper that said as much. Whether the lynx might or might not eat something else as well is beside the point, the lynxes are 1,500 miles from the hares. You simply cannot use the data to support a causal predator/prey relationship.

 

There is clearly some interaction between the two populations given that their numbers closely mirror each other at least some of the time. As previously stated the hares are unlikely to be the lynxs' only food source, especially if the study was conducted over too large an area.

 

When you finally provided some "proof" it was to a webpage that uses as it's first example of Predation Theory, the now known to be wrong lynx/hare data. So that part fails to make the case in favour of the concept of "ecological balance" or cyclic predation theory.

 

The second example on the page was an experiment using Paramecium and to quote from the page;

 

 

So rather than finding an "ecological balance", the system collapsed. The only way to make the results match the "logic and mathematical theory" was to interfere with the system and keep adding prey. This experiment, rather than supporting your ideas directly opposes it.

 

Rubbish! The study also states that such closed and contrived laboratory conditions lack the stability of real world systems due to the lack of complexity. But until they do collapse it clearly demonstrates the coupling between predator and prey numbers.

 

Look JohnB I prefer to accept what the vast majority of the biological community says about predator-prey relationships rather than accept your personal opinion and interpretations on the subject. You sound far to like Andrew Bolt on the subject of climate change for me to consider you as credible.

 

Greg (Not JohnB. My apologies.)

The Lokta-Volterra model of predator-prey cycles is a fantastic model for understanding very simple relationships, hence why it is taught in BIO101. But the truth is that it is not actually a good model for describing the reality of complex ecological interactions. This is because it does not take into consideration the impact of nonlinear dynamics, which can have a profound effect on the stability of a system.

 

This is an old paper, but describes the issue from a mathematical perspective: http://www.jstor.org/stable/1935675

And here's a book on the subject: http://books.google....epage&q&f=false

 

As for what can cause nonlinear dynamics, two examples are saturation of predators in the system and limited resources for either predators or prey even if prey is abundant (this can occur if the prey is good at hiding or defending itself).

 

Just want to edit to clarify: the predator-prey cycle is NOT a fact; it's a model used to describe ecological interactions.

 

The theory of evolution is also a model that is used to describe ecological interactions, but it does not account for random genetic drift within a population.

 

The predator-prey cycle is applied to one relationship between one predator species and one prey species where the latter is the main food source of the former. And it is as good at making predictions about both as is evolution.

 

But in the real world, where things are substantionally more complex and where the predator can eat other prey species some of the time there can never be perfect correlation within the predator-prey cycle.

 

Never the less the predator-prey cycle is as much biological fact as is evolution.

[CharonY]

Never the less the predator-prey cycle is as much biological fact as is evolution.

 

 

This is far from being a fact, depending on the system. That in principle such cycles exist is not the issue, though. The question is whether these are examples of equilibrium systems. And as ecologists have pointed out, there is, as a whole, little evidence for such systems. The experimental recreation is an example of a non-equilibrium hunter-prey cycle, for instance.

[Greg Boyles]

This is like telling someone who's lost 20 pounds in the past year that they need to go on a diet. From a global perspective, humans have been reducing their overall fecundity for the past 20 years and the trend is continuing. Even in African countries, we're seeing a reduction in fecundity. I posted this on another thread, but look up Bongaarts et al. (2009) if you don't believe me.

I don't deny this, but the simple fact is that the reduction in our fecundity is simply not fast enough to avoid a population crash at some point in the near future.

 

And while third world fecundity is slowly reducing, large segments of the third world are rapidly increasing their consuption to western levels - China, India,.....

 

Yes, everyone should be allowed access to contraception, but that is a social justice issue, not an environmental or ecological issue. Policy measures that are specifically formatted to limit fecundity in order to improve environmental sustainability are redundant because, as stated before, FECUNDITY IS ALREADY DECREASING. Moreover, given human life spans, it wouldn't have a measurable effect in the next 50 years anyways.

 

Seeking to reduce global fecundity further is not at all redundant becuase it is not declining fast enough with current strategies.

 

On another vein, when you make grand statements about the impact of the global human population on the world, you're limiting your ability to see the local patterns that affect ecological sustainability. Different ecosystems have different carrying capacities. The technology used to grow agriculture can drastically affect the carrying capacity of a specific location. There are some situationsin which a large population is actually necessary to keep an agricultural system sustainable.

 

Your statement might have some validity if we lived in a world where citizens remained for life in their own countries and consumed only those resources they could obtain from their own territories.

 

But that is clearly not the case is it Jess?

 

Acquisition of resources outside their territories allows populations of countries to expand beyong the long term ecological carrying capacity of their territories. Particularly in the west and our mining acivities and our provision of emergency aid to third world countries undergoing famines etc.

 

I've said it before and I'll say it again: improving the sustainability of the world will not occur if we focus on decreasing the global population size. That's like thinking you can reduce the deficit by simply cutting programs.

 

You can also reduce the cost of each programs by reducing the population and therefore the demand for each of them. Then you don't have to cut any of them.

 

As Kelvin Thompson says about Australia's CO2 emissions......"It is hard to reduce your carbon foot print while you are continually adding more feet".

 

There is only so far that you can go in increasing efficiency and decreasing individual consumption.

 

Let's take water consumption. A person need a minimum of about 2L of water per day to survive. You cannot decrease water consumption any further than that. But if population growth continues then at some point you will STILL run out of fresh water and people will start dieing regardles of how 'efficiently' we are consuming it.

 

While increasing in efficiency and decreasing personal consumption is essential in the short term, it is not an excuse to continue avoiding the morally difficult issue of how are we to reduce our population as rapidly and as humanely as possible.

 

This is far from being a fact, depending on the system. That in principle such cycles exist is not the issue, though. The question is whether these are examples of equilibrium systems. And as ecologists have pointed out, there is, as a whole, little evidence for such systems. The experimental recreation is an example of a non-equilibrium hunter-prey cycle, for instance.

Well I disagree with your interpretation and I don't think there is any profit in debating this any further.

Edited August 2, 2011 by Greg Boyles

[JohnB]

An areas of science that are well established and widly accepted this becomes just silly.

 

Firstly you haven't shown in any way that this idea is "well established and widely accepted". Secondly your argument is a logical fallacy. "Appeal to belief". This is about science and it doesn't matter what people believe or how many accept it, evidence and proof is all that matters. If the idea that ecological balance is so widespread and so widely accepted, then it should be extremely easy to provide some sort of proof, but you don't do so, all you do is repeat yourself.

 

The onus is not on me to provide proof but on you to do the background reading and therefore ask sensible and worth while questions.

 

Second logical fallacy. "Burden of Proof". You have made the claim, the burden is on you to prove it, not on me to investigate.

 

There is clearly some interaction between the two populations given that their numbers closely mirror each other at least some of the time.

 

Third logical fallacy. "Ignoring a common cause". I note also that you either don't know (were you sick the day they taught Methodology 101?) or are ignoring the basic scientific principle, "Correlation does not prove causation".

 

Rubbish! The study also states that such closed and contrived laboratory conditions lack the stability of real world systems due to the lack of complexity. But until they do collapse it clearly demonstrates the coupling between predator and prey numbers.

 

The study doesn't say that at all. It posed a question using a very important word.

The question then arose: why are predator-prey cycles in nature apparently stable, while laboratory cultures quickly collapse?

 

Note the word "apparently", meaning "appear to be". Now it could be that ecologies in the wild are stable and that this is due to the greater complexity, or it could be that they are not, but appear to be from our limited perspective. (To borrow from physics, time is always constant to the subject, but is infinitely variable to the observer depending on relative velocities.)

 

The thing is that in an ideal world with ideal conditions, I would actually agree with you, the numbers should find some sort of balance, that seems only logical. But this is the real world and it doesn't have ideal conditions and so they don't. Nature is not constrained by what we humans consider logical or right. Nature does what it damn well wants to regardless of our theories and ideas. Ecologies are obviously strongly coupled non linear systems, to attempt to reduce them to simple linear relationships is just ludicrous.

 

Look JohnB I prefer to accept what the vast majority of the biological community says about predator-prey relationships rather than accept your personal opinion and interpretations on the subject. You sound far to like Andrew Bolt on the subject of climate change for me to consider you as credible.

 

I'm not asking you to accept my "personal opinion and interpretations" on the subject, you are asking me to accept yours. All I'm doing is asking for proof that you are correct, something that even though you keep saying is easy, you are flat out refusing to do. As to Bolt, who gives a tinkers damn what he might or might not think on a totally different subject? Your fourth logical fallacy for that post. "Guilt by Association".

 

Greg, this is a science forum and deals with evidence and proof, not hearsay. Nobody is exempt not even the mods. "Nullius in Verba".

Edited August 3, 2011 by JohnB

[Greg Boyles]

Firstly you haven't shown in any way that this idea is "well established and widely accepted". Secondly your argument is a logical fallacy. "Appeal to belief". This is about science and it doesn't matter what people believe or how many accept it, evidence and proof is all that matters. If the idea that ecological balance is so widespread and so widely accepted, then it should be extremely easy to provide some sort of proof, but you don't do so, all you do is repeat yourself.

 

 

 

Second logical fallacy. "Burden of Proof". You have made the claim, the burden is on you to prove it, not on me to investigate.

 

 

 

Third logical fallacy. "Ignoring a common cause". I note also that you either don't know (were you sick the day they taught Methodology 101?) or are ignoring the basic scientific principle, "Correlation does not prove causation".

 

 

 

The study doesn't say that at all. It posed a question using a very important word.

 

 

Note the word "apparently", meaning "appear to be". Now it could be that ecologies in the wild are stable and that this is due to the greater complexity, or it could be that they are not, but appear to be from our limited perspective. (To borrow from physics, time is always constant to the subject, but is infinitely variable to the observer depending on relative velocities.)

 

The thing is that in an ideal world with ideal conditions, I would actually agree with you, the numbers should find some sort of balance, that seems only logical. But this is the real world and it doesn't have ideal conditions and so they don't. Nature is not constrained by what we humans consider logical or right. Nature does what it damn well wants to regardless of our theories and ideas. Ecologies are obviously strongly coupled non linear systems, to attempt to reduce them to simple linear relationships is just ludicrous.

 

 

 

I'm not asking you to accept my "personal opinion and interpretations" on the subject, you are asking me to accept yours. All I'm doing is asking for proof that you are correct, something that even though you keep saying is easy, you are flat out refusing to do. As to Bolt, who gives a tinkers damn what he might or might not think on a totally different subject? Your fourth logical fallacy for that post. "Guilt by Association".

 

Greg, this is a science forum and deals with evidence and proof, not hearsay. Nobody is exempt not even the mods. "Nullius in Verba".

 

As previously stated JohnB, I simply don't accept you interpretation of the wording of the study or nor the conclusioons you draw from it.

 

The fact that the author used the phrase "appears to be stable" is not proof that the appearance of stability is nothing more than illusion.

 

And the fact that this single study found that lynx and hare are not perfectly coupled in a predator prey relationship does not amount to proof that there is no coupling in other predator - prey relationships.

 

The fact that you would jump to such a sweeping conclusion based on a single paper (lynx vs hare) makes it quite clear to me that you have little or no formal science education!

 

You appear to be responding to the lynx vs hare paper as many people do to opinion pieces by social commentators. But a scientific consensus is not arrived at based on a single scientific paper that possibly casts some doubt on a prevailing theory.

Edited August 3, 2011 by Greg Boyles

[JohnB]

The fact that you would jump to such a sweeping conclusion based on a single paper makes it quite clear to me that you have little or no formal science education!

 

That's the best you can do? Borderline ad hom?

 

Is that how you normally react to people who ask you to actually back up what you say?

 

You've made it plainly obvious to all that you are interested in neither discussion nor facts, but only wish to be able to repeat any concept that comes your way without fear of contradiction. If that's what you want I suggest you go back to the "Bob Brown Fan Club", you won't last long here. Try the local office of the "Greens", you can have a nice herbal tea and expound sagely to others who will simply nod, agree and continue their circle jerk.

 

I'm done here.