On Tue, 2 Aug 2005 23:07, Thomas Bridgeland wrote:

>On Tuesday, August 2, 2005, at 08:09  PM, Keith Thomas wrote:
>> CO2 with modern equivalents. He found that today's plants had the
>> lowest levels of calcium, copper, iron, potassium, magnesium,
>> sodium, sulphur, and zinc than at any time in the last three
>> centuries."
>
>This may just be a fertilization effect. CO2 is a plant nutrient. When
>the level is high, plants grow faster and so other nutrient levels are
>lower. Same thing is true if you use lots of N. Anything that speeds
>plant growth will have this effect.
>
>Co2 levels have risen and fallen quite a bit over the course of time.
>Currently they are in the lower end of the range. Plants are adapted to
>much higher levels than current.

Over last 400,000 years (that is, since well before the arrival of Homo sapiens), CO2 levels have
varied with the ice ages in a band of 200-250 ppm for over 90% of the time.  Here's a graph:

http://en.wikipedia.org/wiki/Image:Carbon_Dioxide_400kyr.png

CO2 levels were, in fact, below current levels for the entire Neogene, which takes us back beyond
the earliest Australopithecus. If you go back further you'll find the CO2 levels were much higher,
but the past 5 million years is good enogh for me.  There's a graph here covering the entire
Phanerozoic:

http://en.wikipedia.org/wiki/Image:Phanerozoic_Carbon_Dioxide.png

>> Plants are adapted to much higher levels than current.

Not necessarily.  But the point is, are the animals that feed off these supersize plants adapted to
live off them?  The answer appears to be No, from the experiments that have been done.  The
feeders had to eat far more plant material to get the nutrients they required for survival.  They did
their best, but most just didn't make it.  Check the article for details.

"Paleofood" implies Paleo quality plants and Paleo quality plants require a Paleo quality climate.
The link is clear and direct.  So, just as we lobby for grass fed beef, so we should also be lobbying
for massive cuts in CO2 emissions.  Current predictions are for a 6 degree Celsius rise in global
average temperatures by 2070. Doesn't sound much? The last ice age occurred with temperatures
only 5 degrees Celsius below the present.

It's time for Paleofeeders to get political!

Keith