Geography Reference
In-Depth Information
extensively terraced hill slopes. The terraces had the
important role of conserving the fertile soils, thereby
allowing farmers to grow subsistence cereal crops during
the wet season as well as tree crops (e.g. coffee) as cash
crops. These terraces also formed part of an extensive
water control system that allowed the farmers in the
mountains to control the flow of water down on to the
Red Sea coastal plains, or Tihama. In the Tihama, the
farmers managed the movement of water through their
fields using channels and bunds, but always under the
control of each village's 'water master'. This water carried
vast quantities of fertile silt from the mountains, which
naturally fertilised the fields in the Tihama. This is a highly
seasonal system, typical of semi-arid environments,
which is dependent on the reliability of the annual rains
and careful water management. The release of water
from the mountains was not only controlled by the action
of the terraces but also by the rain-green subtropical
woodlands that formed the natural vegetation in the
western mountain ranges of Yemen and southwest Saudi
Arabia (see Figure 13.1)
The combination of two factors—rural depopulation
and domestic energy demand from urban areas—has
compromised this centuries-old soil and water
management system, which was central to Yemeni life.
Rural depopulation is a recent phenomenon that has
been stimulated by labour demands created by the oil
industry in Saudi Arabia and the Gulf states. The affect
of rural depopulation on the rural production systems
has been twofold. First, peak labour demands at various
times in the farming calendar have not been met.
Consequently, some terraces have been abandoned
and are not maintained. Once the terraces fall into
disrepair, their soils and water-retaining functions are
compromised. More violent floods occur throughout the
entire water management system, and soil erosion rates
on the mountain slopes increase markedly. Second,
capital remittances from the migrant workers have
promoted the purchase of small pumps. These are now
extensively used to irrigate for year-round cultivation
using groundwater reserves in small intermontane
basins. The immediate impact of pumping on
groundwater levels has been to lower the water table.
In the Dhamar region, groundwater levels declined at
a rate of 30 cm/year during the 1980s. A further, less
obvious impact is that as farmers have turned their
attention to irrigation they have abandoned yet more
terraces.
Most of the forest that the Yemeni mountains
supported were lost many centuries ago. The remaining
subtropical woodlands have been more or less
destroyed over the past few decades by biofuel
(fuelwood and charcoal) extraction. Biofuel dependency
is very high in Yemeni households (Table 13.1), and fuel
wood supplied 54 per cent of final energy consumption
in 1988 (ESMAP 1991). The greatest demand exists in
the cities, and biofuel supply chains have been
developed between wood collection areas and the
cities. The key characteristics of these supply chains are
markets where main roads cut through or run close to
wooded areas, transport along the main roads from
supply area markets to cities, and urban markets.
Combined, these provide mark-ups of between 33 and
52 per cent of the retail price of fuel wood in urban
markets (ibid.) . The high costs of wood fuels in Yemen,
compared with other western Asian and African
countries, has stimulated this trade. However, an even
greater stimulation has been provided by the
construction of the road network in Yemen during the
1970s and 1980s, which brought many wooded areas
within an economically viable zone of wood extraction
for the cities (Millington and Crosetti 1989).
Table 13.1 Household fuel use for the northern governorates of Yemen, 1998, in
thousand tonnes oil equivalent
The destruction of these woodlands not only causes
problems in meeting the domestic energy requirements in
Yemeni cities. The loss of woodland on non-terraced slopes
increases soil erosion and runoff rates on these slopes,
thereby contributing to increased, uncontrolled flooding
in the Tihama, and it reduces infiltration rates, thereby
further reducing groundwater recharge.
Search WWH ::




Custom Search