Geoscience Reference
In-Depth Information
substitute for manure, by burning them in the so-called Mediterranean hormigueros
—
elds covered with topsoil.
These Spanish hormigueros were traditionally used as a complementary fertil-
izing method which produced Potassium, and incorporated charcoal into the soil in
order to improve its bacterial populations.
70
This was part of the ancient European
Mediterranean culture of
small charcoal kilns made in
re,
71
that took advantage of the summer water stress
which meant that large quantities of dead biomass could not fully decompose and
tended to accumulate in forests or scrubland until ignited by lightning. This
accounts for the fact that Mediterranean woodlands have always coexisted with
natural
res.
72
Thus, the removal of this dead biomass from scrub and forests in
order to burn it on cropland was a sound human adaptation to natural conditions. In
order to provide soil nutrients, however, the thermal process was a less ef
cient way
of decomposing biomass compared to the humid method by means of compost or
manure. Furthermore, it was a very labour-intensive fertilizing system. These fea-
tures would explain why the hormigueros were only practised in the most populated
and cultivated regions of the Iberian Peninsula. In any case, a complete replacement
of the traditional poly-cultural mosaics by a vineyard monoculture would have
entailed a serious bottleneck in nutrient availability, together with a rapid reduction
in the energy return on energy invested (EROI) up to an index of around one or
below. Of course, these local tendencies could have been offset by fertilizer
imports, or by substituting tractors for animal traction but, once again, this would
have meant a higher amount of external inputs and a further decrease of EROI.
73
As Mart
nez Alier reminded us, the theoretical foundations of this double-edged
market sword were forwarded as early as 1902 by Leopold Pfaundler, in his attempts
to assess Earth
í
s maximum capacity for sustaining human needs. He argued that any
estimate would depend on whether we were to aggregate the maximum local
capacities of each small territory, where limiting factors vary; or whether we were to
consider Earth as one territory, assuming that any local resource would be available
globally from any place without transport restrictions. Pfaundler suggested that a
reasonable answer would lie somewhere between the two extremes, noting that
transport always consumes energy and produces environmental impacts.
74
Looking
at the abovementioned Catalan case study, the low energy return on energy inputs of
0.21 that we have found presently, appears to be in keeping with Pfaundler
'
s
argument.
75
The most noticeable feature at present is the fact that current energy
fl
'
ows are not in proportion to the land area in which the agricultural systems are
placed. The metabolic chains operate in a monoculture pattern or in linear livestock
breeding systems that have become virtually unconnected with the surrounding
70
Tello et al. (
2012
).
71
Pyne (
1997
).
72
Grove and Rackham (
2001
).
73
Cuss
ó
et al. (
2006a
).
74
Mart
nez Alier (
1990
).
75
Cuss
ó
et al. (
2006b
).
í
