Geoscience Reference
In-Depth Information
progress was modest on the whole. Water and windmills, invented respectively
3 centuries BCE (as recent research suggests) and in the 7th century CE, were the
main innovations in the energy basis of the agrarian civilisations. Although
important from a technological viewpoint, these changes added very little in terms
of energy availability: ordinarily no more than 1
2%.
8
-
1.3.4 Main Features of the Organic Vegetable Economies
Although several important differences exist among the three ages of our organic
vegetable past, there are also some analogies; especially when dealing with the
relationship between humans and environment. The dependence of this energy
system on soil
implies several constraints to the possibilities of economic
development.
1. Reproducible sources Vegetable energy carriers are reproducible. They are
based on solar radiation and since the Sun has existed for 4.5 billion years and
will continue to exist for 5 billion years, vegetable materials may be considered
as an endless source of energy. Organic vegetable economies have been sus-
tainable since solar energy allowed a continuous
ow of exploitable biomass.
However, only a negligible part of solar radiation reaching the Earth, less than
1 %, is transformed into phytomass by the vegetable species. Of this 1 %, only
an insigni
cant part is utilized by humans and working animals. On the other
hand, increase in the exploitation of phytomass was far from easy. The avail-
ability of more vegetable sources implied extension of the arables and pastures
and the gathering of
cult to transport over long dis-
tances. The ways of utilizing the phytomass were also in con
rewood, which was dif
ict, since more
arables implied less pastures and woods. Thus, while the availability of these
carriers was endless, their exploitation was hard and time consuming. The
production of phytomass was, furthermore, subject to climatic changes both in
the short and long run and heavily in
uenced by temperature changes and
weather variations. Long-term climatic changes could also raise or diminish the
extent of cultivation and wood productivity. Past organic vegetable economies,
based on reproducible sources of energy, were the economies of poverty and
famine.
2. Climate and energy Given that, in pre-modern organic vegetable energy sys-
tems, transformation of the Sun
s radiation into biomass by means of photo-
synthesis was fundamental and since the heat of the Sun is not constant on
Earth, the energy basis
'
of any human activity was subject to
changes. Climatic phases have thus marked the history of mankind. The
availability of phytomass deeply varied and strongly in
—
phytomass
—
uenced human econo-
mies. Glaciations caused a decline in available energy and therefore in the
8
On the quanti
cation of water and wind power see Malanima (
1996
).
