Fjölrit RALA - 05.12.1999, Blaðsíða 112

110
Desertification in Mongolia
plowed farmland and inffastructure. The remainder is covered by water, glaciated and
rocky areas.
Total area used for agricultural production is estimated to be 125 million ha or 80%
of national land area. The greater part of this area is used for extensive grazing. Not
more than 2.5% of the total area is considered to be suitable for arable use (1.7 million
ha) and for production of hay (2.0 million ha). Total cropland is put at 1.3 million ha
with some 0.8 million ha under crops each year.
About 10% of the land surface of Mongolia, equivalent to some 15 million ha are
covered by various types of forest with larch (73.6%), cedar (13%), pine (8%), birch
(5%) and other species (fir, aspen etc.) dominating in the northem part of the country
and saksaul (Haloxylon ammodendron) forests spread in the arid and semi-arid parts
of the country, accounting for 28% of the forest cover. Most forests are considered to
be critical for watershed protection. Cutting of forest combined with the increasing
use of surface water for various economic activities in addition to climatic factors has
caused signifícant reductions in the average flows of many rivers.
The depletion of water resources
The impact of human activities and regional droughts on water resources in Mongolia
over the past several decades has been profound. Water use for irrigation, mining etc.,
and human activities in watersheds such as deforestation. have resulted in substantial
reductions in river flows and flow regimes, water level reductions or complete drying
of many lakes, and lowering of ground water tables. For example, the annual average
flow of the Tuul river has been reduced by 32% and roughly half of this reduction
may be attributed to the cutting of 270 km2 of forest in the watershed of this river 40-
50 years ago.
It was reported (Batjargal 1992) that several lakes in the southem part of Mongolia,
for example. Onggyn Ulaan, Orog, Dzagyn Shal, have been severely depleted or have
dried out completely. But since 1993, the situation has changed due to less intensity of
drought and most of those lakes have already been recovered. In addition to the obvi-
ous ecological disruption caused by lake drying or level reductions, human economic
activities on lake-shores, such as the mowing of reed for fodder, have significantly
impacted the ecology and wildlife of many lakes.
The human induced factors of land degradation
Land degradation induced by anthropogenic factors is common to all ecological zones
of Mongolia. There are several specific human activities that have led to serious and
widespread soil erosion and land degradation.
Crop cultivation is an important reason of soil erosion. Spring tilling coincides with
the season of intensive wind and most cultivated areas are devoid of trees or other
wind breaks. In the Gobi region the average wind speed is 3-4 meters per second or
even more which can cause significant soil moisture loss and erosion. It is estimated
that over the past 30 years, an average of 35-50 tons of soils have been lost from each
hectare of cultivated land due to erosion. Half of all cultivated land in Mongolia is
considered to be degraded to some degree of erosion. New land brought under culti-