76 E.F. Viglizzo et al. Agriculture, Ecosystems and Environment 83 2001 65–81
meat and milk, and vice versa. However, this in- verse relationship is not so evident in areas where the
environmental conditions rainfall and soil quality improve; e.g., towards the eastern pampas Viglizzo,
1986. Productivity and sustainability were also in- versely related in the long term Viglizzo et al.,
1995. Nitrogen in soil was the factor selected to demonstrate this, which was related to the so-called
storage function. Its size in agro-ecosystems depends on the capacity of leguminous pastures to incorpo-
rate atmospheric N. Other attributes of soils could have been selected for quantifying the storage func-
tion, such as organic matter and structural stability of soils. According to this scheme, the larger the
size of the storage function, the greater the long term sustainability of a system Viglizzo and Roberto,
1998.
The historical conversion of grazing areas into croplands in the pampas, has provided a strong em-
pirical evidence of trade-offs between productivity, stability and sustainability under real farming condi-
tions. Productivity has increased all over the region at the expense of stability and sustainability, and
this effect was particularly noticeable in the semi- arid western lands where climate conditions are more
variable Viglizzo, 1986; Viglizzo et al., 1991. This behaviour was consistent with principles of eco-
logical succession: the successive transformation of natural grasslands into pasturelands and croplands
represents for ecologists Odum, 1969 a backward movement to younger, more productive, less stable
and less sustainable stages in the ecological succes- sion. Man displaced the system away from mature,
less productive, stable and self-sustainable stages in dynamic equilibrium, towards younger and more pro-
ductive ones that can render a higher and short-term economic income. Although man can be considered
itself an ecological factor, its impact should be anal- ysed in isolation because of human-based utilitarian
purposes.
4. Lessons and applications
4.1. Lessons History has demonstrated that two sequential
phases normally explain the increase of food and fibre production in most regions of the world in re-
sponse to growing demands: the first characterised by an increasing allocation of land to agricultural activi-
ties, and the second by the intensification of farming on existing lands. The two phases were observed in
Europe, North America and Asia Rabbinge and van Latesteijn, 1992. Nowadays, intensive land use is
being reconsidered because of nutrient contamination of soil and water Carpenter et al., 1998, and recla-
mation of land for other purposes, such as landscape conservation, biodiversity protection, recreation, etc.
Van Latesteijn, 1993. Until the beginning of the 1990s, the pampas of Argentina were still undergoing
the first phase. The land useland cover pattern, as well as the energy flow and the nutrient dynamics of
this period, appear to be promising attributes to learn ecology from. Useful lessons can be summarised as
follows: 1. Although there is a lack of direct evidence,
changes in land useland cover provide indirect means to evaluate the historical fragmentation
of habitats, and infer its consequences on bio- diversity. Well-documented evidence Freemark,
1995; Milne, 1996; Tinker, 1997 has shown the effect of agriculture on habitat fragmentation and
biodiversity. Land use and land cover factors in this study provide indirect indicators to iden-
tify, quantify and locate temporal and geographic fragmentation.
2. Energy flow analysis can be used to compare the productivity of ecoregions, and to assess their
potential response to agricultural modernisation. Heterogeneity of ecoregions and their diverse re-
sponse to agricultural change, are expressed by en- ergy input, output, and output–input relationships
Table 2. The energy flow also provides useful indicators to describe and predict the trade-offs
between productivity and stability. The more in- terconnected the energy pathways, the more stable
and less productive a system is. Given that the complex metabolic structures of cattle production
have a higher energy cost but also the capac- ity of channelling external perturbations among
interconnected pathways, their productivity is lower but more stable than the simple structures
of crop production Viglizzo, 1994; Viglizzo and Roberto, 1998. History has demonstrated that
land use change in the pampas that has determined
E.F. Viglizzo et al. Agriculture, Ecosystems and Environment 83 2001 65–81 77
different patterns of productivity and stability, were in practice an adaptive response of farmers to
cyclical environmental conditions Viglizzo et al., 1997.
3. The case of nutrient dynamics in the pampas is especially interesting. Given that chemical fertili-
sation was rarely used due to unfavourable price conditions, contamination by nutrient overloading
was negligible. Nutrient depletion of soils was, on the other hand, the principal and more extensive
problem. Since nutrient imbalances have accumu- lated over time, fertilisation would had been neces-
sary to maintain the system sustainable in the long term. But this did not happen. Negative balances of
N, P and K in Table 3 illustrate the magnitude of the problem in different ecoregions and periods. In
spite of technology adoption, yields of some crops have reached a plateau towards the 1980s Viglizzo
and Roberto, 1994, raising a concern about the long-term sustainability of agriculture. Investiga-
tions have demonstrated that trade-offs between productivity and sustainability measured through
nutrient balance, have been evident in the pampas. The nutrient balance offers a powerful indicator
to assess sustainability under low input conditions, and even more, because of the high correlation be-
tween the input of fossil energy and the output of N, P, and K, the energy analysis also provides a
way to elucidate and predict the fate of these criti- cal nutrients.
4.2. Applications Agro-ecological indicators derived from land use
land cover, energy flow and nutrient dynamics anal- ysis have a potential value for applying the lessons
from ecology. They can contribute to emerging fields of natural resource administration, such as environ-
mental monitoring, environmental accounting, eco- logical certification, land evaluation and allocation,
and land administration. Some applications are the following:
1. The historical evaluation of changes in land use,
land cover, energy flow and nutrient balance can serve to implement a long-term, indicator-based
monitoring system for the pampas. Current condi- tions and trends of critical ecological attributes can
be analysed by displaying the monitored variables across different temporal and geographic scales. A
well-founded monitoring system is key to project the agricultural change, and predict its environmen-
tal impact. Environmental impact evaluation will as well-benefit from such tools.
2. Environmental accounting and auditing represent a forward step that derive from monitoring. Indi-
cators from monitored ecosystems can be utilised to estimate changes in the natural resource endow-
ment. For example, nutrient gains and losses in the pampas, and their corresponding economic valua-
tion, can be estimated from annual balances of N, P and K. Given that they are not converted into
money, neither public nor private accounts show the current environmental cost of agriculture. Such es-
timation could be done by converting the change of the nutrient endowment into fertiliser-price equiv-
alents.
3. Agro-ecological certification is a modern tool for assessing the quality of products and processes
in agriculture, that have an increasing commercial value. Trade barriers as well as commercial ad-
vantages will be associated with the environmental implication of farming processes. Technical coef-
ficients for eco-certification can be obtained from factors that quantify land useland cover, energy
flow and nutrient dynamics of selected areas. Eco- logical auditors can benefit from these coefficients
for improving the certification work.
4. Land evaluation and land allocation are linked processes that aim at improving conditions for land
administration. Land evaluation is the process of predicting the potential use of land on the basis of
its attributes Rossiter, 1996. Traditionally, land evaluation had a pedocentric view FAO, 1989
that has been widely dominated by soil scientists and technicians. Nowadays, information sciences
have introduced a multidisciplinary perspective that comprises human, economic and environmen-
tal dimensions that are added to the conventional, soil-based one Rabbinge et al., 1994. Given that
different clients may demand different realistic alternatives for land evaluation, proper technical
coefficients need to be supplied Bouma, 1996. The analytical method in this study is a source of
technical coefficients to evaluate the land under an agro-ecological view. The following step is to
make land allocation studies through mathemat-
78 E.F. Viglizzo et al. Agriculture, Ecosystems and Environment 83 2001 65–81
ical models that utilise such coefficients, look- ing for balancing agricultural and environmental
goals. 5. Finally, land administrators can also benefit from
the presented analytical procedure and results to prevent undesirable environmental outcomes of
non-proper land management. The right interpre- tation of historical processes in the pampas can be
helpful for identifying environmental risk thresh- olds in different ecoregions, making the future
more predictable. For example, cropland expan- sion with inappropriate soil technology during the
1920s and 1930s in the fragile lands of the central pampas, caused a severe ecological collapse dur-
ing the 1940s. It is unlikely that such an episode can be repeated because soil management has im-
proved, but the current replication of past farming scenarios may call our attention to the appearance
of threshold conditions in future.
5. Conclusions
