Newsgroups: sci.environment

Michael Tobis:
>I am with John here. I would really like to see some objective argument
>for the numbers. I have been convinced by arguments in this newsgroup
>that the impact per individual is not simply related to affluence. 

Then you have been convinced prematurely since it certainly is -- unless
we define "affluence" in a doublespeak manner, so that, e.g. you can replace
consumption of dinner trays and disposable chopsticks made of Indonesian
rainforest with plastic items while keeping "affluence" constant. If we 
ignore the fact that much of consumption and hence of lifestyle has to
change, you can undoubtedly keep some suitable economists' measure of 
"affluence" the same while reducing impact. 

But this is techno-speak. To a Japanese deprived of wooden furnishings
or a musician deprived of instruments made of fine tonewoods, affluence
has been decreased, no matter what an economist or technophile may say.
And this is just one example -- multiply it by every one of the ways in
which humans enjoy or rely on the production or other "services" of natural
ecosystems. Even ecotourism can become a problem when the number of humans
engaging in it becomes large. Every human use of nature has *some* impact,
and if the total impact becomes greater that what the environment can absorb,
it will be degraded. Affluent people are those who make more use of nature
-- buy more things, dispose of more things, move around more and use more
services. All of that adds up to more impact -- provided you hold the 
definition of "affluence" and the technology constant across any
comparison. [Technology of course also factors into impact, along with
affluence and population size. I = PAT is simplest model that makes any
sense at all.]

>It is
>clear to me that much of what we are doing is catastrophic, and in this 
>I presumably disagree with John. But I do not see where you get these
>numbers without an assumption that impact per individual human is nearly
>fixed. Do you have some basis other than intuition?.

I do, namely that even if all habitat conversion ceased today -- and
this could not happen even with a population of 2 billion at current
Japanese, US and European levels of affluence -- the existing converted
area is too large for the extinction crisis to end immediately. Many groups
would undoubtedly continue to decline. We still don't know why some groups
are declining or failing to recover either where no human pressures are
evident or when they have supposedly been removed. There may be more lasting
impacts at work -- e.g. cumulative toxins. Moreover, loss of historical 
range and loss of geographical diversity has condemned many species, 
sometimes to decline or slow loss of diversity, and often to reduced chances 
for speciation: the other side of the extinction crisis is that speciation 
rates cannot be depressed well *below* average.

[Notice that this kind of impact is *not* proportional to dP/dt, but just
to the size of the already converted habitat areas used to support a given
P, and likewise the cumulative amounts of bioconcentrated toxins are simply
proportional to P (over time, for given A and T), not to dP/dt. There are 
many other impacts which are proportional to P, not to dP/dt. Even habitat 
conversion is not proportional to dP/dt, -- since most of it happens to 
provide a steady supply of goods to the existing population. I.e.  it is 
not based on sustainable use. If sustainable use were achieved, habitat 
convertion would be proportional to dP/dt, but there would still be a fixed
impact cost per capita proportional to AT. E.g. every time you flush your
toilet you are making a contribution to that fixed cost per capita.]

The only way to combat all these trends is to boost populations by restoring 
lands as habitat areas for groups in decline or with restricted ranges. 
Inevitably, some of that land will be have to be land that is currently 
productive for humans: agriculture, range lands, and tree farms.

It's not so hard to understand, really -- human population growth has
been bought at the expense (actually, with extremely low efficiency) of 
other populations and of their evolutionary prospects. To increase those
populations and their prospects, we have to give back a lot of what we
have taken. Any child can be brought to understand that, though it seems
that technocentrists cannot be.

>>The issue -- even from an anthropocentric viewpoint -- is *not* "what 
>>level of technology can support what population". It is:  what kind of 
>>world do you want to bequeath our children? What biotic richness, what
>>potential for utility and enjoyment and awakening of spirit do you want
>>to deny to them forever for our own immediate convenience? *That* is 
>>the question which determines what the population goal should be, not 
>>the one McCarthy asks.
>
>I agree that this is the question, and I'd like you to state how you came
>up with your answer. I for one think that our most destructive practices
>can be substantially eliminated without much impact outside a few specific
>"industries". 

This necessarily involves a change in "affluence". Having to separate garbage
for recycling is after all a negative change in "affluence". We may both 
consider it a worthwhile negative change, but there is no point in pretending
that it doesn't involve extra work or cost. 
 
>
>Even if we accept that affluent humans will always be as destructive as
>they are now, it is not clear where your numbers come from.

The idea is to come up with an equilibrium number of humans whose total
impacts will not even reduce the average speciation rate. This means that
much area which is now productive for humans (or has been destroyed by 
them) has to be restored to a higher-diversity state. Some of this restored
area could be used by humans in low-impact ways, but the fact is that
the geographic base for human society is already way too large for long-term
planetary health: the *stable coevolved* limits to human growth are not in 
the future, they are in the past. By "coevolved limits" I mean limits imposed
by the requirement that evolution not be impared, e.g. speciation rates are
not depressed, species are not losing adaptation over time.

As I pointed out above, the current levels of affluence and technology
enjoyed by the 1.2 billion people of the developed world are already
unsustainable. If those levels are to be maintained, a much smaller
population is needed. Comparing ourselves to other animals of like 
weight class and trophic level and taking into account that our 
distribution is worldwide, it seems that the numbers we had in the 
Pleistocene -- a (very) few tens of millions, could be long-term 
sustainable for us. Factoring in the greater efficiency which may be 
possible with technology leads some conservationists to estimate a 
human population of 100 million as a reasonable equilibrium value for
a healthy, diverse biosphere in which evolution is not being impeded.

Compared to them, I am a technological optimist -- I think we could do a
few times "better" than that, but that we *must* err on the side of caution
and take a target below 1 billion. A nominal half billion, in other words.
It leaves us enough people to maintain a civilization of ideas and technology,
while allowing a high standard of living in a world which wouldn't demand
too many personal sacrifices (beyond the obvious reproductive limits). Finally,
I think that humans will never really do well in circumstances that are very
far removed from those we evolved in -- the reason that the US filled up with
pioneers so fast, and that the Trekkies dream of the stars, is that they are
trying to get themselves back into a human habitat (the latter in a manner 
which is foredoomed). In short, *we* have habitat requirements too, for 
psychological and physiological well-being, and those habitat requirements 
are a lot more like the Pleistocene than like our world. That too has to be 
taken into account -- 500 million could still meet those needs, I think,
but not many more.

I often wonder whether our distant decendents will not measure their own 
technological advancement and fundamental wealth by their ability to sustain
*fewer* people at the same (technological) high standard of living -- valuing
life in biotically rich environments more highly. Perhaps they will think 10
million quite enough people, and laugh at timid ideas such as mine. If much 
of the future world is to be restored, there will be a larger sense of human
accomplishment and investment in environments of high diversity than there is
today -- the ardent technophiles of tomorrow may be the ones who want to 
exercise their skills in this direction, and may be the strongest advocates
of lower human population to free up more space for restoration. 

As a practical matter, we should advocate targets for which we might hope
to build a political consensus -- e.g. 2 billion, all the while keeping
alive discussions about the possible need for lower numbers. But the 
discussion should turn on what kind of world we want to leave to our
descendents. We should try to leave a better one -- with its diversity
rewoven. Only a multigenerations-long experience with that reweaving can
teach us what the true equilibrium population size should be. We are just
guessing at it. 

For us, it is much more important to begin restoration, and to get population
headed in the right direction than it is determine the exact number. We know
it's below where we are now, and that is all we really need to know about
it at this point.

------------
Alan McGowen
Newsgroups: sci.environment