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

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Grasslands of the world
farming is almost a monoculture in the steppes. There are three kinds of farm :
Large Commercial, with flocks of more than 6 000; Small and Medium farms in
the drier areas, with 1 000 to 6 000 head; and Subsistence, with fewer than 1 000
sheep. Paddocks are grazed continuously, except for the high elevation (summer
) ranges. Vast areas, with few paddocks, restrict the potential for controlling
grazing. Guidelines for pasture management began in the 1980s, but much work
has been done since on soil-plant-animal relations. Since areas are vast, Decision
Support Systems (DSS) are a new frontier for range management. Development
of agrotourism on sheep farms is incipient, mostly in the Andes.
INTRODUCTION
The vast area of southern Argentina and Chile between latitudes 39° and 55°S
is referred to as Patagonia (Figure 4.1). Almost all of Patagonia’s grazing lands
are on the cool semi -arid steppes of the extra-Andean territory of southern
Argentina (approximately 750 000 km 2 ), extending into Chile around the
Straits of Magellan (Paruelo, Jobbágy and Sala, 1998b; Villamil, 1997) – see
Figure 4.2.
This chapter refers mainly to extra-Andean Argentinian Patagonia , an area
of treeless semi -arid grass and shrub steppes that has been grazed by domestic
ungulates for over a century.
Patagonia is mostly made up of sedimentary landscapes that blend with
volcanic deposits from the Mesozoic and Tertiary eras, unfolding as a series
of plateaus that lose elevation eastward from the Andes (Soriano, 1983). The
Patagonian mesa landscape is interrupted by a series of rivers that flow from
the Andes to the Atlantic, such as the Colorado, Negro, Chubut, Chico, Santa
Cruz and Coyle. Irrigated floodplains in some valleys have allowed the development
of agricultural oases (Table 4.1).
TABLE 4.1
Biozones of Patagonia grouped according to phytogeographical province.
Phytogeographical province Biozone code (1) Dominant physiognomic type Area (km 2 )
Patagonia Kg 11 Semi-deserts 1 95 400
Kf 11 Semi-deserts 2 68 800
Jg 11 Patagonian shrub steppes 134 800
Jf 11 Shrub-grass steppes 99 900
Jd 12 Grass- shrub steppes 43 600
Id 12 Grass steppes 48 600
Monte Hg 11 Scrub lands 48 300
Jh 11 Monte shrub steppes 2 134 500
Ig 4 Monte shrub steppes 1 54 400
Subantarctic Ha 12 Ecotone forest- steppes and mesic grasslands 52 400
Ea 2 Closed deciduous forests 69 100
Agro-ecosystems Gd 12 Irrigated valleys 22 600
NOTES: (1) Biozone codes are those of Paruelo, Jobággy and Sala, 1998.
SOURCE: Paruelo, Jobággy and Sala, 1998. Reproduced by permission of authors and editors of Ecología Austral.