[NatureNS] Birds face longer migrations due to climate change

Date: Sun, 19 Apr 2009 16:30:31 -0300
From: Stephen Shaw <srshaw@DAL.CA>
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&gt;&gt;&gt; 
Quoting "Paul S. Boyer" <psboyer@eastlink.ca>:
> What I find objectionable is reporting speculation as fact.

Hi Paul:  All future predictions could be characterized as 
`speculation` because
they haven`t happened yet.  The question would be whether these future
predictions about climate change are well founded, or are uninformed guesses.

> I would agree that migration is a hard business, and every year  
> numbers of migratory birds do not survive the journey.
>
> We have been in and out of an estimated 22 major climatic variations  
> in the last 2.4 million years, including four very major glaciations. 
>   Each time, fauna and flora have had to adjust, and those who were  
> unable to adjust have presumably been winnowed out long since.  A 
> very minor change in world temperatures probably will not harm birds 
> and other wildlife.

Agreed, some may be able to adjust to minor climatic shifts by evolving
physically or behaviourally, or by withdrawing altogether from the changed
habitat (but some may not). What do you regard as `a very minor change 
in world
temperatures` though? The most extreme prediction I've seen is that the 
average
temperature could climb as high as 6°C by the end of this century, though the
modellers don't think this will be uniform everywhere.  Even a 1°C rise would
have major effects on vegetation and water availability.  As some discussants
on this list about a year ago seemed to agree finally, you can't do this as
calculations on the back of an envelope:  world climate modelling using
supercomputers is a very complex and difficult thing, so like it or 
not, we are
the mercy of expert climate modellers for this `speculation`.  For the average
onlooker though, the before-and-after photographs supporting the worldwide
disappearance of glaciers on the recent TV programme about future water
resources (Nova?) ought to be pretty alarming.

> If we consider the species which have become extinct since  
> colonization, in our area there are rather few.  We don't know what  
> became of the Labrador Duck: it seems to have been uncommon, and the  
> best guess is that molestation in its nesting area may have been a  
> factor.  The Ivory-billed Woodpecker lost its habitat due to drainage 
>  of swamps, and destruction of its forest habitat.  The Passenger  
> Pigeon was killed in huge numbers right at its nesting sites, in a 
> way  which eliminated it, even though it was one of the most common 
> birds  on the Earth.  The Great Auk was also relentlessly persecuted 
> in its nesting area.
> It we were to review all the cases, I think that it would be 
> difficult to find a single bird species in North America which has 
> gone extinct through climate variations.

Quickly glancing through the annotations on the maps in the back of Peterson's
`Birds of Eastern & Central N. Am` (5th ed) reveals that for land birds, ~23
have experienced `serious decline` in the N.E. or generally (e.g. loggerhead
shrike, N. bobwhite, cmn nighthawk, RH Woodpecker) while only ~7 are expanding
in the N.E. (e.g. two vultures, RB woodpecker, N mockingbird).  You may be
correct about actual extinction, but `speculation` about the future of the 23
in the N.E. doesn't look too promising.  I would guess like you that the major
effect here would be habitat loss, not climate change which has accelerating
only relatively recently.  That doesn't mean that a shift of a few 
degrees over
the next few decades won't have a large future effect, though.
  On the lack of significant actual extinction, the aboriginal inhabitants of N
America have been here much longer and originally didn't have the firepower,
horses or metal implements to do as much widespread damage. Nevertheless, on
the commonest hypothesis they are credited with the rapid extinction of nearly
all the large ground animals in N. America at the end of the last ice age (the
case is much stronger for similar extinctions of flightless birds throughout
Micro- & Polynesia during the original progressive colonizations of those
island groups).

> By far more important are
> factors such  as: persecution while nesting; over-hunting for market; 
> introduction  of alien species (competitors and predators); and 
> destruction of  habitat.  There is also the matter of pesticides, 
> which at one time  threatened the Osprey and the Bald Eagle; but we 
> can report that both  those species have recovered markedly.  (I 
> recently observed an eagle  nest which has been producing young for 
> nine years, located in a  populated neighborhood in city of about 
> 250,000 human inhabitants.)

Agreed especially on habitat loss: eyeballing a textbook map (Freeman & Herron
1998, p. 736) comparing forest cover in USA in 1620 to that in 1920, doesn't
give numbers but it looks like this dropped from ~60% to ~5%. However, climate
change obviously will entail habitat change, with some losses and some gains,
so a temperature shift is not some independent variable that does not interact
with anything else.

> Of the major threats to bird life which I just listed, all can be  
> controlled.  Climate cannot be substantially controlled; and the  
> proposals to attempt to do so are an attempt to administer a medicine 
>  which is far worse than the supposed disease.  Can anyone really  
> believe that the world will cut carbon-dioxide emissions by 80% 
> within  a decade, as some politicians have announced as a goal?  That 
> is  absurd!  This is what disturbs me: that the global warming issue 
> has  become not only politicized, but that it has become a 
> state-supported,  established ersatz-religion.  It is propagated in 
> the compliant media,  and taught uncritically to students even in 
> early grade-school.
> Perhaps I should not worry about this, because the public every now  
> and then gets beset by some such raging fad; and ultimately, one may  
> hope, everyone will learn the way things really work, and come back 
> to  reality.  But in the meantime, do we have to make the lessons so 
> darn expensive?
Well this is your polemic.  Overall, if I`ve got it right, you seem to be
arguing (1) that climate/temperature changes in the future are likely to be
relatively small so we shouldn`t worry too much about this, (2) that this has
been vastly oversold almost like a new religion, and (3), that realistically,
we can't do anything about it.
On (1), up from some scepticism maybe 7 years ago, there now seems to 
be almost
universal agreement among scientists in this field (at least those who are not
funded by power industries) that the global climate is going to change 
markedly
in the coming century, due mainly to increasing CO2 and methane emissions from
anthropogenic effects.  Questions from the different models are whether this
means ~2° or up to 6°, and what the time scale is.  Recently, it has looked
like `sooner, hotter, & even higher sea levels`.
On (2) & (3), scientists are low on the influence peddling totem pole and
scientific advis