Agriculture Reference
In-Depth Information
Brazil and Argentina are the most significant: the size of the ag-
ricultural surfaces involved is similar to that of the two other ter-
ritories.
These three areas together contribute 70% of the needs of Paris con-
sumption. The remaining 30% is supplied half by other French départe-
ments and half by foreign countries.
From these data, the environmental imprint of the Paris food supply
can be approximately represented in terms of (i) the land area required
and (ii) per capita nitrogen fl uxes involved, exactly as is currently done
for wastewater domestic effl uents (Fig. 1). To satisfy the needs in vegetal
products of one Paris inhabitant, only 0.05 ha of the territory of the Seine
watershed is required, but 0.33 ha of territory in polycultureanimal farm-
ing areas such as those of Brittany, Normandy and Nord-Pas-de-Calais are
required to satisfy the needs in meat and milk of the same person (although
some surplus crop production in this area is available to supply other re-
gions); in addition, an area of about 0.12 ha in South America is required
to supplement the feed of the livestock in the latter region. This indicates
that by far the largest territorial area required to feed Paris is for producing
animal products. This is not surprising as for the whole of Europe, 83% of
crop production is destined to feeding livestock (Sutton et al., 2011).
To estimate the losses occurring through leaching and volatilisation
from agricultural soils in the two French supply areas, we calculated the
difference between total fertilisation and crop production of agricultural
land (both expressed in N content) at the département scale. The relation-
ship between crop yield and total fertilisation follows an asymptotic curve
(Fig. 2a), with the surplus (i.e. the difference between fertilisation and
yield) increasing regularly with increasing fertilisation (Fig. 2b). The sur-
plus is generally lower in the cereal crop regions of the centre of the Paris
basin than in the intensive livestock farming areas of the West of France. If
the surplus is assumed to be entirely diluted in the infi ltrating water depth
(as a mean 300mmyr
−1
for the areas described herein), the correspond-
ing theoretical sub-root nitrate concentration in water produced by agland
surfaces can be calculated. In most d épartements, the value is far above
the drinking water standard of 11 mgNl
−1
(50 mgNO
3
l
−1
). In these regions,
agland occupies about half the total area.
