8
OUR PLANET MAGAZINE
CLIMATE CHANGE AND THE CRYOSPHERE
South America's rivers make available 35 per cent of the world's
surface water resources. Yet snow and ice still represent an important
additional water supply, providing it to mountain valleys and adjacent
arid and semiarid regions. Mountain glaciers in the Andes and the
Patagonia ice shelf supply water for river flow, lakes and reservoirs.
The rivers flowing to the Pacific Ocean have a remarkable seasonal
regime, fed by snow and ice melt in late spring and summer time.
The dry, desert-like Pacific coastal landscape extending from the equator to
central Chile, and the high plateau of Peru and Bolivia, both depend, in large
measure, on snowmelt water.
At the southernmost tip of South America from 29º south, the dry, arid
conditions are on the eastern side of the Andes, south of the rivers Negro
and Colorado. Low precipitation makes its rivers dependent on the melting
of glaciers and of the important ice shelf between 48º south and 52º south.
Although precipitation is higher there, snowmelt also contributes
to the flow of northern Patagonia's rivers. The economically wealthy
regions of Cuyo, in central western Argentina, and central Chile -- home to
large urban populations and important agriculture, fruit growing (mainly
vineyards), hydroelectricity and industry -- also fundamentally depend on
the melting of snow and ice. Indeed the ancient inhabitant of the region, the
Huarpes, called it Cuyum, meaning `Hell's Desert'. Human activity there only
became feasible when European migrants introduced irrigation, starting the
region's development.
The more advanced pre-Colombian civilizations of the Andean inter-
tropical region, managed their water resources remarkably successfully.
The most developed pre-Inca cultures both complemented reduced and
sporadic rainfall water and improved supplies through wise engineering
works, such as by the measured distribution of irrigation water and by
connecting the Atlantic and Pacific watersheds -- building a 74 kilometre-
long channel for water transfer some 3,000 metres up in Cumbemayo.
Climate change is already beginning to have a critical effect on
the living conditions of Andes indigenous communities, on water
dependent human activities, and on natural ecosystems. The availability
of meltwater will increasingly diminish, damaging sustainable development.
Recent studies show that the Peruvian glaciers may disappear altogether
in the coming decades.
The rapid retreat of the inter-tropical Andean glaciers brings further dangers
to local people, and particularly to the indigenous communities of the
high plateaus of Bolivia, Ecuador and Peru, from avalanches and glacier
lake outburst floods. Peru's 19 glaciated mountain ranges contain more
than a half the world's tropical glaciers, mostly in the Cordillera Blanca.
This danger is much less great further south, in the Patagonian Andes, where
the retreat is taking much longer; though the shrinking of the glaciers is still
important there, it does not bring similar hazards and risks.
The best possible use of the resources and potential energy in the large
amount of water still enclosed in the southernmost glaciers would be
to enable the relocation of productive systems to the more than a half
million square kilometres of the semiarid Patagonian plateau. This would
call for conserving the valuable biological diversity of the region and
developing appropriate technology, and for the wise and rational use of
the large quantities of both surface and underground water resulting from
the glaciers' retreat. It can draw on the experience of the agro-industrial
use of the upper basin of the Rio Negro, which, starting in the 1930s,
made possible its transformation to the remarkable exporter of fruit and
wines that it is today. Grain crops, which will suffer decreases in yields in
Argentina's northern agricultural fields, could be relocated, with planned
adaptation, to the Rio Negro's lower basin and to irrigated lands in other
Patagonian sub-regions. The Institute for the Development of the Lower
Basin of the Rio Negro is already developing the necessary feasibility studies.
The energy for such an undertaking may be provided by local hydroelectric
plants and by the steady westerly winds, already under initial exploitation.
El Niño events will bring important snow mass to the Andes below 29º south.
So there must be planned use of meltwater, a selection of plant species better
snow, ice and life