The Environmental Food Crisis

Melting glaciers jeopardize Asian and world food production

Irrigated croplands, mainly rice, in the watersheds of the In- dus, Ganges, Brahmaputra, Yangtze, Huang He (Yellow River), Tarim, Syr Darya and Amu Darya are all, to varying extents, de- pendent on glacial water and snowmelt from the mountains (Winiger et al ., 2005). With rising temperatures, combined with changes in the monsoon, up to 80% of the glaciated area may be lost within this century (Böhner and Lehmkuhl, 2005; UNEP, 2007). While data are sparse in this region, actual observations from Nepal indicate that current warming at high altitudes is oc- curring much faster than the global average, up to 0.03º C per year (Shrestha, 1999), and even faster at higher altitudes, up to 0.06º C per year (Liu and Chen, 2000; Eriksson et al ., 2008). Scenarios suggest that the effects on the rivers are highly vari- able, ranging from a major increase in annual flow until around 2050 followed by a relatively rapid decline in flow for the Indus , to a gradual decline in flow in rivers such as the Brahmaputra. If temperatures rise quickly, such as >0.06º C per year, the annual flow of the rivers will invariably decline over time, particularly for those dependent on the mountains, but less so for those more dependent on the monsoons (UNEP, 2004; 2007). The irrigated cropland in these basins, which are the most dependent upon the mountains for water flow, comprises ap- proximately 857,830,000 ha (UNEP, 2005; 2008). If average production on irrigated rice is projected at 6 tonnes/ha (range 2–10 tonnes/ha), compared to 2–3 tonnes/ha for non-irrigated land (combined, average about 3.3 tonnes/ha in Asia), the water from the melting Himalayas annually supports the production of over 514 million tonnes of cereals, equivalent to nearly 55.5% of Asia’s cereal production and 25% of the world production today. A reduction of, for example, 10–30% due to increased flood damage to irrigated lands combined with reduced water flow and seasonal drought, would thus lower world cereal pro- duction of 3,000 million tonnes (by 2050) by 1.7–5%, even if we assume no other yield increases in this period (in which case losses would be larger).

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