Geoscience Reference
In-Depth Information
and livestock breeding, as took place in England with the well-known Norfolk four-
course rotation.
85
Here it would be interesting to apply the synthesis proposed by Ronald Lee, of
Malthus
s approaches.
86
'
and Boserup
'
Lee suggests that past
technological
advances usually occurred within a
comprising a limited set of
combinations of population densities and technological capacities, as a response to
'
'
Boserupian space
'
tendencies towards diminishing returns. Only from time to time did
some historical discontinuities occur that pushed forward technological capacities
from one
Malthusian
'
to another.
87
However, this immediately raises the
question: What factors induced these large but unusual technological shifts? As
Bruce Campbell and Mark Overton have stressed, an important side of that issue
lies in knowing how differently pre-industrial societies solved the fertilizing trap,
within several historical contexts and natural endowments.
88
Much more research is
needed in the historical reconstruction of nutrient cycles, based on the methodo-
logical tools that agronomists can offer to historians. This long-term agro-ecological
research must be undertaken without forgetting the diverse natural and climatic
conditions in which very different kinds of
'
Boserupian space
'
devel-
oped. For example, owing to the summer water stress in Mediterranean regions the
strongest limiting factor was not the nutrients but the soil water content.
'
advanced organic agricultures
'
89
ll the nutrient gap opened up by population growth, or a higher
amount in trade and taxes, past
'
advanced organic agricultures
'
had to rely on a
more intense land-use which, in turn, required a higher labour intensity and a longer
time-span of investment.
90
The Chinese way of solving this problem clearly shows
the dilemma usually faced between keeping high yields per unit of land without
diminishing labour productivity at the same time.
91
Here again the role played by
European colonization of America in abolishing this land constraint can be seen.
Any
In order to
assessment would be very limited without extending the time
perspective until the beginning of the 20th century, in order to take into account the
American grain exports from the Great Plains where settlers stopped using fertilizer
for nearly 60 years up to the 1930s.
92
The overseas exports of cheap cereal coming from the United States and other
'
ghost acreage
'
'
, leading to the well-known European agricultural crisis of the late
19th century, were based on large scale soil mining of nutrients stored in the
new Europes
'
85
Shiel (
2006
).
86
Boserup (
1965
).
87
Lee (
1986
).
88
Campbell and Overton (
1991
).
89
Bevilacqua (
2001
) and Garrabou (
2005
).
90
Allen (
2008
).
91
Elvin (
2009
).
92
Cunfer (
2005
) and Cunfer and Krausmann (
2009
).
