3.4.1.5 Improved and adaptive crop cultivars
The development of a wide range of improved cultivars has
been instrumental in the effective use of land in many parts
of the continent. Uganda farmers have developed 60 different
cultivars that have adapted to the production systems
in the central African highlands. AKST has led to similar
improvements in cotton production in the Sahel, maize in
eastern and southern Africa, and wheat in southern Africa.
Work by IARCs and NARIs has played an important role
in mitigating the spread of crop diseases and pests in large
parts of the continent, making it possible for millions of
small-scale farms to use arable land efficiently.
In the arid and semiarid lands of eastern and southern
Africa, AKST has been instrumental in helping farmers select
and manage germplasm for staples. Drought-tolerant
varieties have made it possible for vulnerable farmers to better
use land in areas that are predisposed to extreme rainfall
variability.
3.4.2 Water management
3.4.2.1 Linking water, AKST and development and
sustainability goals
Agricultural production is constrained when water quantity,
quality and timing do not match the water requirements
of crops, trees, livestock and fish. The amount of
water required for agriculture is extremely high compared
with other uses. Massive water use in agriculture has negatively
affected other water users and the environment. Lake
Chad declined from 25,000 km2 in the 1960s to 1,350 km2
in 2001, mainly because of the fourfold increase in water
withdrawal for irrigation between 1983 and 1994 (UNEP,
2002). Dry season flows in most SSA rivers are declining
because of upstream irrigation and reservoirs (UNEP,
2002; Gichuki, 2004). AKST has contributed to unsustainable
water use through: the adoption of higher yield crops
that are water demanding, such as rice; limited attention
to water-saving technology; limited adoption of yieldenhancing
technology in rainfed agriculture; and inadequate
development of technologies to enhance the use of marginal
water sources.
Water resources in SSA are poorly distributed. In 1999,
water was abundant in 53% of Africa’s land area, which
was home to 60% of the population, some 458 million.
By 2025, water-scarce areas are projected to increase from
47% to 64%; these areas would have 56% of the population
but only 12% of the continent’s renewable water resources
(Ashton, 2002).
Over the last 50 years, the water crisis in SSA has intensified.
This is likely to continue, driven partly by:
- Increasing population and per capita consumption.
- Climate change scenarios in southern Africa suggest that seasonal and yearly variability in rainfall and runoff
will increase with some regions getting drier and others
more wet (IPCC, 2007). Vegetation and agriculture
are expected to change in response. These changes are
expected to increase household vulnerability to drought
and flood, with devastating effects on the poor and already
vulnerable (Hudson and Jones, 2002).
- Slow generation, adaptation, adoption and effectiveness
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of AKST. Effective AKST will be expected to provide
solutions that will enable the poor to adapt to changing
circumstances and aid public and private assistance organizations
to make adaptation possible. Food insecure
populations will need to be informed of future climate
prospects and better supplied with resources for water
conservation and development of drought-tolerant
crops.
New and innovative ways of managing water in agriculture
are needed to facilitate continued agricultural growth and
to release more water for other uses, including for the environment.
AKST has contributed to driving changes in four
water management arenas and will be expected to do more
to address emerging challenges:
- Conserving vital water catchments, reducing water pollution
and reversing the degradation of aquatic ecosystems.
- Enhancing water supply by capturing usable flows and
tapping marginal water resources.
- Ensuring equitable distribution and use of water its derived
benefits, with the highest returns to society.
- Increasing net benefits per unit volume of water by reducing
nonbeneficial uses and allocating water to high
value uses.
3.4.2.2 Protecting water resources and related ecosystems
Agricultural growth in many parts of SSA has come at the
expense of forest, grassland and wetland ecosystems and
has contributed to degraded water and ecosystems. Africa
lost 55 million ha to deforestation from 1980 to1995
(FAO, 1997). Cameroon has lost nearly 2 million ha and
Democratic Republic of Congo may be losing 740,000 ha
annually. In just 100 years, Ethiopia’s forests have declined
from 40% to 3% of the land area. Conversion of swamps
and marshlands to cropland and urban industrial establishments
threatens the integrity of aquatic ecosystems and
their ability to provide ecological goods and services (MA,
2005). Fisheries are under threat from declining river flows,
fragmented rivers, shrinking wetlands, water pollution and
overfishing. Poor agricultural land use is blamed for eutrophication
(Bugenyi and Balirwa, 1998).
Inappropriate land management in water catchments
causes most soil erosion. Soil loss ranges from 1 to 56 tonnes
ha-1 yr-1 (Okwach, 2000; Liniger and Critchley, 2007). Subbasin
soil loss varied from 12 to 281 tonnes km-2 yr-1 and
suspended sediment discharge was as high as 200 kg s-1 during
peak flow soil and water conservation measures reduced
soil loss. Soil loss for a conventionally plowed maize field
with no mulch was 32 tonnes ha-1, 10 tonnes ha-1 with 50%
mulch and 2 tonnes ha-1 with 100% stover mulch from the
previous season (Okwach, 2000). In northern Ghana and
Burkina Faso the adoption of savanna and Saharan ecoagricultural
practices reduced soil loss by 10 to 40% and increased
groundwater recharge by 5 to 20%, depending on
their effectiveness and adoption (Tabor, 1995). Appropriate
AKST is available that can reduce degradation of water
catchments, but its access, adaptation, adoption and effectiveness
are limited in most places. |