Browning of Planet Earth -Reply

Bob MacGregor (RDMACGREGOR@gov.pe.ca)
Fri, 17 Jul 1998 10:11:13 -0400

Yes, more CO2 does enhance plant growth, assuming all other factors
remain adequate. However, Lion is partly right about browning.
Actually, a hotter earth means more circulation of water. The downside
is that it also means a higher evaporation rate and, worse, a
rearrangement of climate zones. This may work out as an improvement
for some folks in Russia, China, and Canada, but middle-lattitude people
might well be in the situation Lion describes.
A couple of final notes about this: although prediction of the impacts of
global warming is extremely imprecise, given its long-term nature, the
general consensus is that weather "events" will become more frequent
and severe (ie, more heat energy in the atmosphere equals more severe
storms). Also, the areas close to the equator are not expected to
experience the same amount of change that would occur in the
temperate or near-artic (and antarctic) zones.

A prospective corn farmer in Northern Manitoba might think this global
warming stuff is great, but even wilder fluctuations in annual weather
patterns cannot be good news for prairie farmers, nor would I expect a
water-deficit cotton farmer in Texas to look forward to even hotter, drier
summers.

Unfortunately, I still don't see any reasonable prospect for the world NOT
to consume all the fossil fuels that are economically recoverable (even if
we cut 'way back on our profligate consumption of fossil fuels, someone
else in the world will likely pick up the slack, so we'll still be stuck with
the greenhouse problem). That being the case, what can we do about
the concommitant rise in atmospheric CO2? There is a good overview
of this issue and the various, proposed solutions in the June 1998 issue
of Discover Magazine ("Carbon Cuts and Techno-Fixes").

In Canada, it is estimated that agriculture directly contributes about 10%
of greenhouse gas emissions (CO2, CH4, N20). If you take into account
all the industrial emissions upstream (ie, input industries) and
downstream (eg, food transportation, processing and distribution), I'd
guess that current agri-food _system_ contributes in the 1/4 to 1/3 range
of total greenhouse gas emissions.

Carbon storage (sequestration) in soils has been discussed on this list
before; generally, the low- or no-chem folks are 'way ahead of the pack
here. Similarly, the lower-input ag and local marketing people likely
consume fewer fossil fuel calories -- and therefore have fewer
emissions -- than the conventional/chemical ag folks. Still, before the
sustainable ag folks get too puffed up with pride, consider that very few
farmers do not use internal combustion engines for production and/or
distribution of their produce. Also, as was discussed before on this list,
per food calorie moved, a small truck going to a local farmer's market
might contribute a lot more emissions than a trainload -- or semi-trailer --
of veggies going halfway across the country. Finally, a lot of the
contribution of agriculture to greenhouse gases is CH4 from livestock
(especially cattle burps and farts); I haven't yet heard that organic
cattle produce less methane than typical feedlot cattle.

Its a very complex topic and there aren't any simple solutions. It is
certainly worthwhile to take the time to poke holes in the one-sided,
misguided, misleading, and short-sighted propaganda of the
power/mining industries about the wonderful benefits of more CO2.
Keep up the good work.
BOB
rdmacgregor@gov.pe.ca

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