Agriculture Reference
In-Depth Information
all N used in food production that is not in the crop product is lost to the
environment.
3.3 THE CURRENT NITROGEN IMPRINT OF PARIS FOOD
CONSUMPTION
Until the middle of the 20th century, Paris was still mainly supplied by an
area roughly corresponding to a 150-km circle around the city, including
most of the Seine watershed. Although a certain degree of agricultural
specialisation was already present within this area, the agricultural sys-
tem was fundamentally based on a close relation between cereal culti-
vation and livestock farming, the latter producing the organic fertilisers
required by the former. The increase of grain yield during the 19th century
mostly resulted from an improvement in animal feeding and manure man-
agement, owing to the replacement of the triennial fallow by a N
2
-fixing
legume fodder crop, which provided a considerable increase in livestock
density (Billen et al., 2009, 2011).
The 20th century agrarian revolution, following the generalisation of
the use of synthetic N fertilisers, led to pronounced spatial segregation be-
tween the regions of the central Paris basin—specialised in cereal cultiva-
tion at the expense of livestock farming—and the more peripheral regions,
which specialised in cattle rearing and imported a large share of the feed
from other regions, countries or continents. Today, Paris's main food-sup-
plying area is composed of three areas with quite different biogeochemical
functioning (Billen et al., 2011):
1. The directly surrounding area corresponding to the Seine water-
shed is now mainly devoted to intensive cereal farming and pro-
vides most of the vegetal proteins consumed in Paris. It exports
82% of its production.
2. The area made up of Brittany, Normandy and Nord- Pas-de-Calais
produces the largest fraction of the animal proteins consumed in
Paris, but depends on massive imports of feed from other regions.
3. Among the imports of vegetal proteins required for feeding the
livestock of the latter territory, soybean and oilcake meals from
