The Virtue of Forests, Virgin and Otherwise 
While deforestation continues in the tropics, 
a few temperate forests are returning. 
We may need them more than we know 
by Hazel R. Delcourt 
When a part of North America’s 
remaining forestland is cleared for cul- 
tivation, when its trees are felled for 
timber or ravaged by blight or fire, 
many people regret the loss of habitat, 
property, life, and natural beauty. 
Less often considered but of vital im- 
portance is the release of carbon that 
also results from the loss of vegetative 
cover. Plants, through photosynthesis, 
convert carbon dioxide to carbohy- 
drates and can thus store carbon 
within their tissue. This storage is only 
temporary, as vegetation ultimately 
releases carbon back to the atmos- 
phere through decomposition. Forest 
vegetation accounts for approximately 
90 percent of the vast amounts of car- 
bon stored in the biomass of terrestrial 
ecosystems. Forty percent is currently 
contained within the temperate and 
boreal regions of the world. The re- 
mainder is concentrated primarily in 
tropical forests, which typically have 
greater average biomass and can thus 
store more carbon. Current concern 
over the possible global effects of in- 
creasing concentrations of atmos- 
pheric carbon dioxide must therefore 
take into account the effects of chang- 
ing land use on the distribution and 
cycling of carbon. 
Most discussions about the growing 
problem of atmospheric carbon diox- 
ide center, not on living vegetation, 
but on fossil fuels (primarily coal, oil, 
and natural gas — the fossilized re- 
mains of photosynthesizing organ- 
isms). Since the early 1800s, the ever 
increasing use of fossil fuels has lib- 
erated tremendous quantities of car- 
bon dioxide. The world’s oceans and 
diminished forests cannot provide an 
endless sink for this carbon, and ap- 
proximately one-half the carbon di- 
oxide gas produced each year from 
human activities now accumulates in 
the atmosphere. With the current rate 
of increase in the use of fossil fuels, 
atmospheric carbon could double in 
as little as fifty years. Many scientists 
anticipate that as a result, the average 
global temperature will rise, perhaps 
by 2°C. The wide range of effects 
of such a warming could include melt- 
ing of the polar icecaps and shifts 
in climatically suitable crop zones. 
What many people don't realize is 
that the amount of carbon released 
by industry every year is equal to less 
than 0.5 percent of the total reserve 
carbon held in vegetation and soil. 
This implies that relatively small 
changes in the area or productivity 
of the world’s vegetation can have a 
great impact, for better or for worse, 
on the carbon balance. Unfortunately, 
over much of the earth’s surface, soils 
are currently being degraded and for- 
ests cut down at an alarming rate. 
And deforested areas, in addition to 
no longer being able to absorb carbon, 
are themselves sources of carbon. 
Land clearance in the tropics, for ex- 
ample, which is proceeding at an es- 
timated rate of one percent of the 
land area every year, may contribute 
half again as much carbon dioxide 
as is released by the combustion of 
fossil fuels. The preservation of all 
possible reservoirs, or sinks, of carbon 
has become critical, and detailed stud- 
ies of the world’s temperate forests, 
to identify areas where intensive forest 
management can enhance carbon ac- 
cumulation in the future, may prove 
of great value. 
Inventories of current carbon re- 
serves in temperate forests give us a 
snapshot of one moment in a long his- 
tory of forest change. They provide 
only a static picture of a dynamic 
process. To place this process in per- 
spective, we need to understand the 
historical alterations of forest eco- 
systems that have led to the present 
distribution of biomass and carbon. 
Before reconstructing the carbon dy- 
namics of a region, we must estimate 
the carbon pool existing at the start 
of the time period being considered. 
Carbon losses resulting from defor- 
estation and cultivation and carbon 
gains resulting from reforestation can 
then be documented. Finally, we can 
determine the changes in carbon stor- 
age, taking into account both losses 
and gains of carbon through time. 
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