August 01, 2006

Article at Cosmos Magazine

OPINION | A Climate of Change

El Castillo, also known as the Temple of Kukulcan, is a Mesoamerican step-pyramid that dominates the centre of the Chichen Itza archaeological site in the Mexican state of Yucatán

By Wilson da Silva

IT’S IN OUR NATURE to be optimistic. Every day, we make decisions that show our underlying optimism: we have children, buy houses, make new friends, and look forward to better days.

It may be how we got ourselves from the plains of Africa to dominance over the planet. In a ridiculously short time — two hundred thousand years, or just 0.004 per cent of Earth’s history — we have gone from a new species to global overlords. We’ve grown accustomed to thinking that tomorrow will be better than today, and have worked hard to make it so.

Until recently, that is. Maybe we’re so used to ‘tomorrow’ being better than ‘today’, that we don’t even think about it anymore. How else would you explain the fact that our best scientists are forecasting a future that will be worse than today — with increasingly nasty weather, less reliable water supplies, and diminishing crop yields — and yet, we don’t even seem all that concerned?

Part of the problem is that we have been conditioned to only worry about a small ‘time window’; no more than a few years. This was very important as we developed civilisation: how crops did over a season or two was a good indicator of how they might do in the future. But thinking in terms of decades, or centuries, is difficult for humans.

Which is why, when the climate changed in Mexico between 750 AD and 950 AD, and a long drought reappeared, the Mayan civilisation collapsed. In that period, there were three severe droughts, each lasting between three and nine years. From pollen trapped in ancient layers of lake sediment, we know that just before the Maya fell, tree pollen disappeared almost completely and was replaced by weed pollen. 

Why? Widespread deforestation.

Without trees, soil erosion intensified, carrying away fertile topsoil. It’s estimated that the changing ground cover would have boosted regional temperatures by as much as 6°C, further drying out the surrounding land, and placing greater pressure on crops. Rising temperatures would have also disrupted rainfall patterns.

Yet, archaeological evidence suggests that the Maya had faced and overcome just such a series of droughts some 600 years earlier when their cities were temporarily abandoned. But their population recovered, cities were reoccupied and their culture blossomed.

The Maya were very successful, at their height supporting a population of up to 13 million people. But previous knowledge of a cyclical, century-long dry spell was not recorded. When it returned, their already struggling culture was pushed over the edge.

It’s not just a cautionary tale from history. Last year we saw how quickly a city can fall, when Hurricane Katrina hit the proud and seemingly mighty city of New Orleans. A year later, it hasn’t recovered much, despite the billions of dollars that have been spent.

Many of the problems we face today are not insurmountable, but they are challenging. The biggest one is electricity – we may take it for granted, but electricity is the lifeblood of modern civilisation; it is also accounts for 37% of greenhouse gas emissions. What’s worse, demand for electricity is expected to increase by 43% over the next 20 years.

Yet, it is also an opportunity: by rapidly transitioning our electricity production away fossil fuels like coal and gas, we would remove a very big source of emissions. 

Is it worth the pain? The Maya might have thought so.