Scientific bulletin n° 331 - October 2009
© IRD / Jacques Servain
razil’s Nordeste region,
an extensive steppe
called the “Sertão”, is
home to over 50 million,
28% of the country’s
population living on 12%
of its surface area, is one
of the world’s most heavily
populated semi-arid zones.
The rural population is
severely deprived and
people live from
subsistence rainfed
agriculture, mainly
growing beans and maize.
Food security is therefore
closely dependent on the
rainy season, which is
extremely erratic in the
region. The amount and
frequency of precipitation
can fluctuate enormously
from one year to the next.
This inter-annual
variability in rainfall is
mainly controlled by the
sea-surface temperatures
of the tropical Pacific and
Atlantic. Aiming to assess
the impact of these
temperatures on
production of maize and
beans in this Northeast
region, an IRD researcher
and his Brazilian partners
of the Fundação Cearense
de Meteorologia e
Recursos Hídricos
(FUNCEME) compared the
trends in these two
variables between 1952
and 2000. Their findings
are useful for building
prediction scenarios for
annual yield at the onset of
each rainy season.
© IRD / Laure Emperaire
B
Brazil’s Northeast
under the vagaries of the oceans
El maíz, o «milho», y el frijol llamado «feijão» son los dos principales recursos alimentarios en el Sertão. Dos
cultivos pluviales por definición muy sujetos a los riesgos climáticos.
Except along its coast, reputed for having
some of the most beautiful beaches in the
world, Brazil’s Northeast region Nordeste
is semi-arid and supports only sparsely
growing cacti and stunted bushes in the
“Sertão” or backlands. The rural population
livelihood is traditional subsistence
rainfed agriculture, devoted mainly to
beans and maize. However, these two
staple crops saw their production fall
dramatically in the 1980s and 1990s,
bringing chronic famines and rural
exodus towards the large cities on the
coast and in the South of the country.
An IRD researcher and his partners from
the State of Ceara’s Fundação Cearense
de Meteorologia e Recursos Hídricos at
Fortaleza studied the impact of climate on
production of maize and beans in that
State. Their findings are frustrating for the
region’s farmers: unfavourable conditions
lead to very poor yields, yet supposedly
“ideal” conditions do not necessarily bring
good harvests.
When the oceans get involved
The rainy season in the Nordeste lasts
just four months, from February to May.
During this time the area receives over
60% of the total annual rainfall. The pattern
is linked to the southerly migration of the
intertropical convergence zone1, whose
position depends strongly on the sea-surface
temperature variability in the tropical Pacific
and Atlantic. Any “anomalous” climatic
situation over these two oceans around
December or January leads to a latitudinal
shift of the zone and a disturbance of
seasonal rains over the Sertão some
weeks later. For example, drought episodes
in the Nordeste are often associated with
El Niño. Conversely, La Niña can bring on
extremely abundant rain and even flooding
in this otherwise dry region.
Agricultural vulnerable
Apart from the strong seasonal constraint
the region lives under a high inter-annual
variability. Some years can be very wet,
like 2009, others extremely dry. Agriculture
Institut de recherche pour le développement - 44, boulevard de Dunkerque, CS 90009
F-13572 Marseille Cedex 02 - France - www.ird.fr
You can find IRD photos concerning this bulletin, copyright free for press,
on www.ird.fr/indigo
CONTACTS:
Jacques Servain
director of research at the IRD
jacques.servain@ird.fr
UMR Laboratoire
d’océanographie et du climat :
expérimentations et approches
numériques – LOCEAN (IRD,
CNRS, Muséum National
d’Histoire Naturelle, Université
Pierre et Marie Curie - Institut
Pierre Simon Laplace)
Address:
Université Pierre et Marie Curie
aile 45-55 4ème étage
Case 100 - 4 Place Jussieu
75252 Paris Cedex 05, France
Brazilian partner:
FUNCEME
Av. Rui Barbosa, 1246 - Aldeota
60115-221 Fortaleza
Brazil
http://www3.funceme.br
REFERENCES:
Alves J.M.B., Servain J.,
Campos J.N.B. Relationship
between ocean climatic
variability and rain-fed
agriculture in Northeast Brazil.
Climate Research, 38 (3), p.
225-236, 2009
KEY WORDS:
Brazil, Northeast Brazil
(Nordeste), food security,
climatic variability
PRESS OFFICE:
is particularly vulnerable, confronted by this
highly erratic climatic situation. Aiming to
evaluate the impact of the climate variability
on harvest quality and quantity in the
Nordeste, the research team first retraced
the history of the region’s agricultural
variables for the second half of the past
century. They used agronomic data on the
two crops collected by the Instituto Brasileiro
de Geografia e Estatistica between 1952
and 2000 and compiled by the Instituto de
Planjeamento do Ceará on the planted
area, annual production, yield, price and
aggregate value (price/yield).
The planted area quadrupled in 50 years,
closely in line with the growth of the rural
population, rising from 150 000 hectares
in the early 1950s to 600 000 ha at the end
of the XX th Century. The investigations
revealed two distinct periods. The planted
area first increased continuously until the
end of the 1970s. Then in the early 1980s,
the region underwent several consecutive
years of drought. Yields and production of
maize and beans fell dramatically and never
recovered their previous levels in spite of a
renewed rise in the 1990s.
Favourable conditions no guarantee of
good harvests
The researchers next compared the variations
in the harvests with the sea-surface temperature variability of the tropical Pacific and
Atlantic. Series of oceanic events that
induce severe spells of drought in Brazil’s
Northeast, in other words an El Niño episode
on the Pacific added to abnormally high
sea-surface temperatures in the North of
the tropical Atlantic and abnormally low
ones in the South, are generally associated
with very poor harvests. However, the
reverse does not necessarily correlate with
optimal conditions for agriculture. Parado-
xically, “good” conditions -abundant precipitation in the Nordeste, involving a La Niña
episode on the Pacific combined with a
negative sea-surface temperature anomaly
in the tropical North Atlantic and a positive
one in the South- do not necessarily produce
good harvests. In fact, depending on the
distribution of precipitations during the rainy
season, the equivalent total quantities of
water can have highly variable consequences on the harvests. Thus for example,
bacteriological epidemics or insect proliferation are often associated with extremely
abundant rainfall. Production is then hardly
any higher than normal.
This conclusion highlights the fragility of
agriculture in Brazil’s Nordeste. The strong
intra-seasonal and inter-annual variability
in rainfall is only one of the factors which
burdens farming in the region. The often
extreme poverty of the rural population,
a low level of mechanization, the rarity
of irrigation systems -which in any case
are often inappropriate, the sporadic
use of inputs, are some of the factors
which restrict crop yields.
Although it evidently will not resolve these
structural problems, the research on the
relationships between climate and agriculture
will at least enable farmers in the North-East
to judge better the most appropriate time
for sowing, estimate forthcoming yields and
as far as possible prevent bad harvests.
Agricultor nordestino y su hijo. La población rural vive
de una agricultura de subsistencia, principalmente
consagrada al frijol y al maíz.
Los efectos benéficos de la lluvia en el Sertão : colecta
de agua en el paisaje resecado.
Rédaction DIC – Gaëlle Courcoux
Translation - Nicholas FLAY
1. The intertropical convergence zone is a belt of a
few hundred kilometres wide, where the trade
winds converge and low pressures, high cloud cover
and strong rainfall occur. This zone varies on either
side of the Equator depending on the apparent
movement of the sun during the course of the year.
Vincent Coronini
+33 (0)4 91 99 94 87
presse@ird.fr
© IRD / Pierre Gazin
Scientific bulletin n° 331 - October 2009
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