Brazil's Northeast Under the Vagaries of the Oceans
ScienceDaily (Jan. 23, 2010) — Except along its coast, reputed for having some of the most beautiful beaches in the world, Brazil's Northeast regionNordeste 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 .
The beneficial effects of rain in the Sertão: water collection pond in the dried-out landscape. (Credit: Copyright IRD / Pierre Gazin)
When the oceans get involved
The rainy season in the Nordestelasts 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 zone (1), 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 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 XXth 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.
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Relationship between ocean climatic variability and rain-fed agriculture in northeast Brazil
José Maria Brabo Alves1,*, Jacques Servain2,3, José Nilson B. Campos1
1Fundação Cearense de Meteorologia e Recursos Hídricos (FUNCEME)/Departamento de Engenharia Hidráulica e Ambiental, Centro de Tecnologia, Universidade Federal do Ceará (UFC), Av. Rui Barbosa 1246, Aldeota, 60115-221 Fortaleza, Ceará, Brazil
2Institut de Recherche pour le Développement (IRD), UMR-182, LOCEAN, Université Paris-6, 4 Place Jussieu, Tours 45-55, Case 100, 75252 Paris Cédex 05, France
3Present address: Fundação Cearense de Meteorologia e Recursos Hídricos (FUNCEME), Av. Rui Barbosa, 1246, Aldeota,
60115-221 Fortaleza, Ceará, Brazil
*Email: brabo@funceme.br
ABSTRACT:
The statistical relationship between sea-surface temperature variability over tropical oceans and the 1952 to 2000 crops of maize and beans in the state of Ceará, Brazil, was investigated. This region mainly receives precipitation from February to May. The climatic indices used were the Niño-3 for the Pacific and the dipole index for the Atlantic. In a first series of diagnostic analyses, the climatic precursor variables were examined from November to January (Years 0 to 1) for the Niño-3 index and from February to April (Year 1) for the Atlantic dipole components. The agronomic variables were the planted area, annual production, yield (which showed a negative linear trend during the study period), price, and aggregate value (price/yield) for Year 1. A more robust statistical weight was obtained with the Atlantic dipole. The Pacific weight added to, or decreased, the Atlantic effect, depending on the sign of the index. Ocean climatic conditions that generate drought episodes in the Nordeste region of Brazil are generally associated with bad harvests. However, the reverse (i.e. wet weather episodes) does not necessarily produce good harvests. In a second series of prognostic analyses, a statistical model used the ocean climatic information available before the rainy season to forecast the yields of maize and beans. The model gave some relevant data in terms of yield tendencies, and was more sensitive when the climatic conditions were neutral or dry. Remarkably good yield forecasts were noted at the end of the study period. Harvests depend on complex combinations of multiple climatic criteria related, not only to quantitative, but also qualitative factors connected with the rainy season.
KEY WORDS: Climate variability · Northeast Brazil (‘Nordeste’) · Climatic impact · Rain-fed agriculture
KEY WORDS: Climate variability · Northeast Brazil (‘Nordeste’) · Climatic impact · Rain-fed agriculture
