Agriculture Reference
In-Depth Information
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was followed by a recovery in NDVI values to more normal levels in 1985.
Drought evolved slowly in early 1983 before reaching a peak in 1984 when
NDVI was 35% below normal.
Millet and sorghum are the staple crops in this semiarid region of Africa.
Millet production for Mali, covering the period 1981-2000, is shown
in figure 5.7b. The NDVI data showed that 1984 was the year of the
most severe drought, resulting in the lowest production in 20 years, about
500,000 metric tons of millet. This was the lowest point over several years
of progressively decreased production from 1980 to 1983, following years
of persistent drought during the 1970s.
The spatial pattern of NDVI anomalies for 1984 (figure 5.8) shows a
region-wide drought across the Sahel region, from Senegal to Sudan in the
east, with NDVI anomalies ranging well below normal:
−
20% to as low
[69],
as
80% in Chad. This drought led to large-scale famine, starvation, and
loss of human life and livestock.
−
Line
——
*
21.
——
Norm
* PgEn
Ea
st Africa
Most of East Africa has a bimodal rainfall distribution and hence two
agricultural growing seasons. The short growing season typically begins in
late September and ends in November. The long growing season typically
begins in February or March and continues through May or June. Figure
5.9 shows the evolution of monthly NDVI vis-à-vis the long-term monthly
NDVI mean for Kenya (East Africa) for 1983-86 and 1996-99.
Like rainfall, NDVI values over East Africa exhibit a bimodal pattern,
with maximum values in April and November. This pattern follows the
evolution of both the long and the short rainy seasons that are governed by
the Inter-Tropical Convergence Zone (ITCZ), following the twice-yearly
solar passage over the equatorial zone. For 1983 and 1984, the monthly
NDVI values for both short and long rainy seasons were lower than the
[69],
Figure 5.8
Spatial variation in NDVI anomaly across the Sahel region during the growing
season of 1984.
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