It’s not just carbon that changes climate

I wrote some months back about the drought in California, which incidentally came to a watery end in November and December. That said, reservoirs and I daresay the water table remain depleted and vulnerable to future below-average rainfall. However, this short piece is about climate change driven not by carbon emissions but by deforestation, this time in South America.

It is a story that has gone largely unreported until a few weeks ago but which highlights the interrelated nature of our climate, ecosystem and lifestyle.

The giant Cantareira reservoir system in Brazil supplies water not only to the 9 million inhabitants of one of the world’s mega cities, Sao Paulo, but also to hydroelectric power stations. At present, the reservoir is at an astonishing 5% of capacity.

The rainy season lasts from November to April but with inflows at only 1/6 of average in January, the remaining few months will need to be very wet indeed to replenish the reservoirs

This is quite obviously serious, resulting in the need for water rationing but also, in a country where 70% of the electricity comes from hydropower, power cuts. However, while the issues of population growth and demand control are interesting, more so is the suggested reason for the precipitous fall in water resources.

It is suggested that the drought is a consequence of deforestation within the amazon basin. It is argued that the Atlantic winds pick up moisture from the rainforest before releasing it as the air encounters the rising peaks of the Andes in the catchment areas of the rivers supplying the reservoirs around the Sao Paulo areas.

As the forest cover has diminished so has the moisture transfer to the westward bound air, resulting in a reduction in rainfall. The rainy season lasts from November to April but with inflows at only 1/6 of average in January, the remaining few months will need to be very wet indeed to replenish the reservoirs.

If there is a positive aspect to this story it is that it is uniting local groups in opposition to the continued deforestation of the Amazon rainforest. The reaction of the political leaders in government will be a sign of Brazil’s understanding of the importance of its rainforest but also its willingness to embrace the environmental agenda.

Back in 2001 a similar drought led to the construction of fossil fuelled power stations, understandable in the short term but rather missing the point. Let us hope that a more long term holistic strategy is followed this time.

Nick Cullen is a partner at Hoare Lea