Grasslands of the World.pdf - Disasters and Conflicts - UNEP

J.M. SUTTIE
Grazing management in Mongolia 293
Plate 7.16
Small stock grazing through snow – Tuv.
• Black zud occurs when, in winter , there is a prolonged lack of snow and continued
want of water because of freezing of surface sources, so both stock and
herders suffer from lack of water to drink. This type of zud does not occur
every year, nor does it usually affect large areas. Wells provide water in black
zud conditions, but often a long trek would be necessary and, at the wells ,
shelter and bedding would not be available in the camping area.
• White zud is caused by deep and prolonged snow cover (Plate 7.16). It is a
frequent and serious disaster that has caused a great number of deaths. Opinion
on how deep snow has to be to constitute zud varies: over 7 cm causes difficulties
in Khangai yak pastures, while up to 10 cm leaves fodder accessible to
small stock in the forest -steppe and steppe; in the steppe of less mountainous
provinces, 6 cm is considered a zud. White zud is, of course, more serious if it
follows a dry summer and herbage is short.
• Storm zud is caused by continuous snowfall and drifting over large areas. If
it occurs at the coldest time of year it is very dangerous; animals may run
many kilometres before the wind and most mortality is through exhaustion
or falling into rivers.
• Khuiten zud is caused by extreme cold or freezing winds; when winter temperatures
are 10°C below seasonal averages, stock can no longer graze freely,
and expend much energy in maintaining body heat. It usually occurs when
night temperatures drop sharply for two or more consecutive nights. Serious
losses occur when khuiten zud follows white or storm zud.
Drought , from the herders’ viewpoint, is a lack of rain during the warmer
part of the year. Drought in late spring and early summer is the most serious
since, at that season, the pasture recommences growth and the animals are in