500
A. Vushe
sediment that is deposited in river channels, behind dams, and estuaries. Conservationists must find cost-effective ways of harvesting sediment, e.g., by using sand
traps, desilting surface water reservoirs, and assessing the feasibility of desilting and
reusing the fertile silt/mud to rehabilitate degraded arable lands, and using infertile
sand for construction in urban settlements. Probably, regulating trade in reclaimed
river sediments may solve the problem of illegal sand mining (for use in construction)
that has caused degradation of surroundings of many African towns.
Efforts to improve soil fertility, reduce erosion, and manage sediment to protect
surface water resources must incorporate diversified production, enhanced reforestation, and pasture revitalization. Regulating livestock populations, planting grasses,
reforestation, and afforestation of grazing lands with carefully selected indigenous
plants that can fix nitrogen, and tolerate salty soils and droughts may succeed in
reversing the deterioration of pastures. A good case study was conducted in four
villages in the Mount Moorosi area in Lesotho, where communities successfully
rehabilitated rangelands by constructing physical barriers on the mountain slopes
to slow runoff, trap sediment, and promote water infiltration. Significant obstacles
to rehabilitation of communal pastures in large catchments demand well-informed
livestock management practices, policies, and community participation facilitated by
broad participation in self-regulating systems which include guidance on stocking
levels and community education. Research is required for refinement of regulations
and their enforcement, and analyze use of property and land-use taxes to generate
funding for conservation. Scholars have suggested the introduction of soil conservation incentives (such as loans), land reclamation bonds, soil loss, and legal liability
for water pollution and liability insurance (UNEP 2007). These approaches have
been used successfully elsewhere, but their introduction to Africa (e.g., communal
areas) may require modifications.
Many streams and rivers are drying up quickly at the end of rainy seasons due
to erratic and low rainfall, but siltation and deforestation of catchments (especially
in riparian zones) could also be contributing factors. A long-term observed effect
(indigenous knowledge) is that some wetlands, springs, and streams in semi-arid
areas of Africa dry up whenever riparian vegetation like water berry (Syzygium
cordatum) has been cleared. One hypothesis is that water-use-efficient riparian trees
provide cool shades over the wetlands, springs, and shallow water channels which
reduce evaporation rates. This means that evapotranspiration could be less than evaporation in a forested riparian zone with indigenous trees that are water use efficient. If
scientifically proven, this hypothesis could lead to one method to protect riverbanks
from erosion and shade streams and springs to reduce water evaporation through
reforestation of the riparian zones with water use-efficient vegetation. This could be
upscaled in riverbank protection and water conservation efforts. Research would be
required for selecting a wide range of desirable traits in trees and grasses that are
appropriate for the targeted environment, seedling production, and afforestation of
degraded and deforested areas with the plant species that are economically lucrative
and easy to propagate in each river basin. These traits and uses could include floods,
drought, and salinity tolerance; rooting systems that aid conservation of soil and
water; food security; wood fuel and/or timber production; medicinal uses; etc.
A. Vushe
sediment that is deposited in river channels, behind dams, and estuaries. Conservationists must find cost-effective ways of harvesting sediment, e.g., by using sand
traps, desilting surface water reservoirs, and assessing the feasibility of desilting and
reusing the fertile silt/mud to rehabilitate degraded arable lands, and using infertile
sand for construction in urban settlements. Probably, regulating trade in reclaimed
river sediments may solve the problem of illegal sand mining (for use in construction)
that has caused degradation of surroundings of many African towns.
Efforts to improve soil fertility, reduce erosion, and manage sediment to protect
surface water resources must incorporate diversified production, enhanced reforestation, and pasture revitalization. Regulating livestock populations, planting grasses,
reforestation, and afforestation of grazing lands with carefully selected indigenous
plants that can fix nitrogen, and tolerate salty soils and droughts may succeed in
reversing the deterioration of pastures. A good case study was conducted in four
villages in the Mount Moorosi area in Lesotho, where communities successfully
rehabilitated rangelands by constructing physical barriers on the mountain slopes
to slow runoff, trap sediment, and promote water infiltration. Significant obstacles
to rehabilitation of communal pastures in large catchments demand well-informed
livestock management practices, policies, and community participation facilitated by
broad participation in self-regulating systems which include guidance on stocking
levels and community education. Research is required for refinement of regulations
and their enforcement, and analyze use of property and land-use taxes to generate
funding for conservation. Scholars have suggested the introduction of soil conservation incentives (such as loans), land reclamation bonds, soil loss, and legal liability
for water pollution and liability insurance (UNEP 2007). These approaches have
been used successfully elsewhere, but their introduction to Africa (e.g., communal
areas) may require modifications.
Many streams and rivers are drying up quickly at the end of rainy seasons due
to erratic and low rainfall, but siltation and deforestation of catchments (especially
in riparian zones) could also be contributing factors. A long-term observed effect
(indigenous knowledge) is that some wetlands, springs, and streams in semi-arid
areas of Africa dry up whenever riparian vegetation like water berry (Syzygium
cordatum) has been cleared. One hypothesis is that water-use-efficient riparian trees
provide cool shades over the wetlands, springs, and shallow water channels which
reduce evaporation rates. This means that evapotranspiration could be less than evaporation in a forested riparian zone with indigenous trees that are water use efficient. If
scientifically proven, this hypothesis could lead to one method to protect riverbanks
from erosion and shade streams and springs to reduce water evaporation through
reforestation of the riparian zones with water use-efficient vegetation. This could be
upscaled in riverbank protection and water conservation efforts. Research would be
required for selecting a wide range of desirable traits in trees and grasses that are
appropriate for the targeted environment, seedling production, and afforestation of
degraded and deforested areas with the plant species that are economically lucrative
and easy to propagate in each river basin. These traits and uses could include floods,
drought, and salinity tolerance; rooting systems that aid conservation of soil and
water; food security; wood fuel and/or timber production; medicinal uses; etc.