As glaciers melt in the Andes, western areas of South America can expect a period of repeated, extreme flooding that will later give way to drought conditions, creating new challenges for millions of people, researchers warn.
Tropical Andean glaciers and high-altitude ecosystems are vital to the economies of Peru, Ecuador, Colombia and Bolivia. The 8 million inhabitants of Peru’s capital Lima depend on them for drinking water. The Bolivian capital, La Paz, takes 30 to 40 percent of its drinking water from glaciers in the Cordillera Real.
Glacial water powers hydro-electric generation and feeds agriculture in all four countries, while supporting biodiversity in the high Andes.
The upper part of the mountain range is especially sensitive to global warming because atmospheric temperatures tend to rise faster at high altitudes than at sea level.
A 2006 study published in Science found that the surface temperature in the Andes rose by 0.11 degrees Celsius per decade from 1939 to 1998, nearly twice the global average of 0.06 degrees per decade during the same period.
And a 2008 study by the State University of New York and the University of Massachusetts predicted another 4.5 to 5 degree jump by the end of this century.
Rising temperatures are melting the Andes glaciers. They are also wiping away the paramos - the cold and moist high-altitude grasslands that cover mountainsides just below the glaciers – according to Carlos Daniel Ruiz, a researcher with the International Research Institute for Climate and Society (IRI) at Columbia University and a professor at the Escuela de Ingeniería de Antioquia (School of Engineering of Antioquia) in Medellin.
Glaciers and paramos control the level of water in Andean rivers, letting it flow during the summer and trapping surplus water during rainy seasons. But in Colombia’s Los Nevados National Park, unusually strong storms and hail are washing out the organic layers of delicate soil in the paramos. Ruiz says rivers are showing higher sediment loads - evidence of erosion - even where there has been no human intervention.
Flooding will be the first problem for Andean countries – especially in Peru, where glacial retreat has already sent excess water cascading down the Cordillera Blanca to Huaylas province in Ancash region.
Fast melting water can cause high-altitude lagoons to overflow or even destroy them, says Wilson Suarez, a researcher at the Peruvian Meteorological and Hydrological Service, SENAMHI . Large blocks of ice and rocks can also tumble from shrinking glaciers into lagoons - a real risk in the seismically active Andes - unleashing flash floods.
Peruvians already know that danger well. In May 1970 an earthquake triggered an ice avalanche, unleashing a flash flood that killed 20,000 people in the town of Yungai.
Since then, Peru has been monitoring its mountain lagoons and has even carved out tunnels to drain water from some of them. When an ice avalanche hit Lagoon 513, near the town of Carhuaz in April 2010, tunnels drained away overflow and people had time to flee the area. The flood killed farm animals and destroyed 20 houses, but no humans died.
Worsening flooding will be followed by water shortages and, eventually, drought - starting 20 to 50 years from now in different parts of the Andean region, predicts a study by the Montpellier-based Institut de Recherche pour le Développement (Institute of Development Research) and SENAMHI.
THREATS TO POWER, BIODIVERSITY
That’s when the effect of melting glaciers will start to hit South America’s power supplies too. Hydropower accounts for about 80 percent of electricity generation in Peru, 70 percent in Colombia and 50 percent in Ecuador.
Although geographical conditions vary between power plants, a 2007 World Bank analysis of the El Cañón del Pato hydropower facility in Peru’s Anchash region illustrated what could happen. Losing half of glacier runoff would cut its annual electricity generation by 10 percent, and once the glaciers disappear, power production would drop by 15 percent, it predicted.
Extrapolating those findings across Peru’s other hydro-electric plants, the World Bank forecast that melting glaciers could cost the country’s electricity system $1.8 billion a year once they are completely gone. Peru may be forced to fill the gap with fossil fuels, raising costs in a country already struggling with poverty and emitting even more greenhouse gases into the atmosphere.
But even as people adapt to changing water supplies, Andean ecosystems are likely to suffer permanent damage.
The tropical Andes have more than 30,000 species of plants, about 10 percent of all plant species on earth, and half of them don’t exist anywhere else. Conservation International identifies the region as one of the world’s biodiversity hotspots - areas with high numbers of endemic species that have lost over 70 percent of their natural vegetation.
A warmer atmosphere will put additional stress on these ecosystems. Conservation International says around 800 plant species grow in the paramo ecosystem alone, which are threatened by rising temperatures and erosion.
IRI’s Ruiz explains that high-altitude cloud forests are losing their fog - and thus significant amounts of water - because warmer temperatures cause fog clouds to form at higher altitudes, above the forests’ upper limits. The drying of these forests could lead to the extinction of endangered species of birds and mammals that live there.
And as water becomes scarcer in the long term, tensions over how best to use it are likely to arise. This is expected to place an extra burden on Andean countries as they strive to develop and eradicate poverty.
Santiago Ortega Arango is a Colombian engineer and freelance journalist interested in climate change and renewable power issues. He is an associate professor at the Escuela de Ingeniería de Antioquia and a Fellow in Global Journalism at the Munk School of Global Affairs at the University of Toronto.