PERu's 0.5 percent contribution of greenhouse gases to the world's atmosphere is small, compared to the impact on Peru expected as a result of climate change. Peru is ranked as the fourth country most impacted by climate change. El Niño has regularly affected the 386,102 sq. mi. (one million sq. km.) of Peruvian territory, with droughts in the Andean south, and floods in the northern Pacific coast. These impacts, however, are small compared to the impacts of climate change. The 125 mi. (200 km.)-long White Mountain Range, the world's largest ice-covered tropical range and Peru's main concentration of ice, has been losing volume in the last 50 years. The glaciers are melting, leading to glacier reduction, the formation or increase of glacial lakes, and changes in ecosystem composition. The glaciers of White Range Park have retreated 82 ft. (25 m.) in the last 50 years according to CONIDA, Peru's aerospace agency, and CONAM, the Peruvian environmental agency.

Glacier retreat has implications for downstream river flows. In rivers fed by glaciers, summer flows are supported by glacier melt (with the glacier contribution depending on the size of the glacier relative to basin area, as well as the rate of annual melt). If the glacier is in equilibrium, the amount of precipitation stored in winter is matched by melt during summer. However, as the glacier melts as a result of global warming, flows would be expected to increase during summer—as water is released from long-term storage—which may compensate for a reduction in precipitation. As the glacier gets smaller and the volume of melt reduces, summer flows will no longer be supported and will decline to below present levels. The duration of the period of increased flows will depend on glacier size and the rate at which the gla cier melts; the smaller the glacier, the shorter lived the increase in flows and the sooner the onset of the reduction in summer flows. In 18 glaciers in the Peruvian Andes, mass balances since 1968 and satellite images show a reduction of more than 20 percent of the glacial surface, corresponding to 11,300 million cu. m. of ice, according to B. Morales-Arnao and INAGGA-CONAM.

In addition to the White Mountain Range, 19 mountain range glaciers exist in Peru, which according to a study elaborated by the Corporation For the Development of Santa in 1970, occupied 965 sq. mi. (2,500 sq. km.) These mountain ranges lodge 1,500 lagoon glaciers. The White Mountain Range is one of the most sensible thermometers to measure global warming, showing that in the last half-century the Peruvian mountains have lost hundreds of cubic meters of ice. Peru was hit in 1998 with the destruction of the Machu Picchu hydropower station, and rebuilding costs amounted to $160 million, according to RGS Ltd.

Glacial lakes are formed on the glacier terminus due to the climate change-induced glacier retreating processes. The majority of these glacial lakes are dammed by unstable moraines, which were formed by the glaciations of the cooler period of climate within the last millennium. Occasionally, the lake happens to burst and suddenly releases an enormous amount of its stored water, which causes serious floods downstream along the river channel. This phenomenon is known as glacial lake outburst flood (GLOF). Since 1702, more than 25 catastrophic GLOFs have occurred in the White Mountain Range. They come with little or no warning, and are made up of liquid mud that transports rolling stones and blocks of ice with the capacity to destroy cities and lives. The most serious GLOFs destroyed parts of the city of Huaraz in 1725 and 1941, as well as the GLOF from Lake Jancarurish in 1950. Additionally, two other destructive avalanches from the summit of North Huascarán destroyed, in 1962 and 1970, several villages and caused the deaths of more than 25,000 inhabitants.

sEE ALsO: Floods; Glaciers, Retreating; Glaciology; Peruvian Current.

bibliography. INAGGA-CONAM, Vulnerabilidad de Recursos Hídricos de Alta Montaña (1999); B. Morales-Arnao, "Estudios de ablación en la Cordillera Blanca," Boletín del Instituto Nacional de Glaciología del Peru (v.1/5, 1969); B. Morales-Arnao, "Estudio de la evolución de la lengua glaciar del Pucahiurca y de la laguna Safuna," Boletín del Instituto Nacional de Glaciologiá del Perú (v.1/6, 1969).

Carlos Soria

Universidad Nacional Mayor de San Marcos

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