Climate Change, Environment, Headlines, Latin America & the Caribbean

Rainfall Patterns Can’t Be Ignored in Climate Change Debate

Mario Osava

RIO DE JANEIRO, Jan 17 2011 (IPS) - In discussions of human activities that affect the climate, there is relatively little talk about alterations in rainfall patterns, despite the enormous implications that such changes have on human survival.

For example, torrential rains and mudslides left a death toll of 640 last week just north of Rio de Janeiro — a figure that is bound to grow as corpses are dug out of the mud in communities and towns which civil defence workers have not yet been able to reach.

It was the worst disaster of its kind in Brazilian history. The last time that landslides, heavy rains and flooding claimed so many lives was in January 1967, also in Rio de Janeiro.

In São Paulo as well, a number of neighbourhoods have suffered flooding since last Tuesday — a catastrophe that occurs several times a year in Brazil’s largest city.

But while southeastern Brazil has been hit by torrential rains, the Amazon rainforest and other parts of the country have been suffering drought.

In the second half of 2010, 40 municipalities in the western part of the Amazon jungle that depend on river traffic were in a state of emergency after they were cut off due to a prolonged low water season that made it impossible to bring in food and drinking water by river.

The droughts cannot be blamed on El Niño, a cyclical climate phenomenon arising from a warm Pacific Ocean surface current travelling from west to east along the equator, which was very mild last year, said climatologist José Marengo of the National Institute for Space Research (INPE).

Climatologists are concerned about a string of droughts in the Amazon jungle –three since 1998.

And the extreme southern part of Brazil has also been suffering from drought since last October, which has hurt farmers.

The La Niña effect, the cold-water version of El Niño, is apparently one of the causes, along with a wind route forming a “channel of moisture” towards the southeast, which are causing the heavy rains over Rio de Janeiro and São Paulo, and leading to less rainfall in the south.

There is no consensus on whether the droughts and excessive rainfall are due to global warming, but the current science shows that extreme climate events are becoming more frequent and more intense.

But although rivers, lakes and aquifers are mentioned among the natural wealth of a country or region, the rains that feed these fresh water reserves are not.

Brazilians, for example, boast of the great abundance of the country’s fresh water — 12 percent of the global total is the most oft-cited figure — particularly in the Amazon. But the droughts that have become more frequent have shown just how vulnerable rivers are, regardless of their size.

It is abundant rainfall that has made it possible for Brazil to become one of the world’s leading agricultural producers and exporters, with only about five percent of the country’s farmland needing irrigation. But this advantage could largely be lost, due to deforestation of the Amazon jungle.

Studies underscore the importance of the rainforest in generating, by evaporation and plant transpiration, not only its own rainfall but also a large part of the rains that irrigate vast swathes of land in Brazil and in its neighbours to the south, where the most productive farmland in South America is found.

Winds from the east, already laden with moisture from the Atlantic ocean, pick up more moisture when they cross the Amazon jungle, before turning south after running into the barrier of the Andes.

These are the “flying rivers” talked about by Gerard Moss, a Swiss-born Brazilian pilot whose project of that name shows how air currents that carry water vapour from the Amazon influence rainfall in southern and southeastern Brazil.

Besides collecting samples in his plane for the Flying Rivers project, Moss gives talks and demonstrations on climate change and on how water is carried by the wind, in his effort to raise environmental awareness.

“Attitudes must be changed from childhood,” he told IPS, adding that his goal is to get students to understand these mechanisms and how essential they are to preserving their quality of life.

Farmers in Brazil, Argentina and Paraguay should ally themselves with environmentalists in defence of the Amazon, says agronomist Antonio Nobre, an INPE researcher. Without the rains generated by the jungle, desertification would be the fate of a large part of south-central Brazil, he warned.

The string of droughts in the Amazon, in 1998, 2005 and 2010, could be partly due to deforestation, which has affected 17 percent of the jungle, reducing its capacity to generate the rains that are so essential to vegetation in the region, and threatening to upset the water cycle.

But the global climate, and the system of rains in particular, requires more than just curbing deforestation in the Amazon, Nobre told IPS. He called for reforestation and the restoration of ecosystems in order to recover the lost equilibrium not only in this region but in other parts of the world as well.

It is possible to “unmake deserts” which reflect the loss of balance generated by human activities, the researcher said, pointing out that the scientific knowledge to do so already exists, and citing reforestation efforts that are winning back parts of the Sahara desert.

But China’s failure to curtail the expansion of its deserts shows that monoculture farming does not solve the problem, and that restoration of ecosystems with biodiversity, to restore moisture, is essential, he stressed.

Water vapour in the atmosphere represents a mere 0.001 percent of all water on earth, equivalent to one-tenth of the fresh water in lakes, but 10 to 11 times the water in rivers. The vital role it plays in the water cycle depends on forests, oceans, winds and other factors that are now being perilously altered.

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