Perceptions of Drought

A friend of mine began noticing New Mexico’s drought a couple of years ago when he realized he hadn’t needed chains or snow tires on his pickup truck in a while. He lives up a hilly dirt road, where snow can make it tough coming and going. But he realized he hadn’t been having problems in recent years.

I thought of my friend this afternoon when, while at the library, I stumbled by happenstance across an intriguing paper in the journal Climate Research by a Norwegian researcher named Elisabeth Meze-Hausken on how people perceive climate change in northern Ethiopia(1).

(More below the fold.)

Drought here in the industrialized world is a funny thing. We notice it, and it effects us. Some people suffer economic dislocations. Crops fail, ski areas go belly up, recreational boating is in the tank. But no one in New Mexico is going to die because of what is, statewide, the driest five-year stretch in half a century. Africa is different. Droughts can lead to wholesale migrations of populations, coups, famine and death.(2)

But how do we define drought? And how do we know when we’re in it? The folks in Ethiopia that Meze-Hausken writes about offer a perfect case study in what I’ve made my seat-of-the-pants definition of drought – “less precipitation than you’ve come to depend on.”

Ethiopians do not have the luxury of being buffered from climatic changes by the industrialized built environment. More than 50 million Ethiopians live a subsistence agricultural life, many of them in arid regions. These are the people who are vulnerable to climate variability. These are the people who go hungry when there’s not enough rain. And Meze-Hausken found they believe there is no longer enough rain – that their climate is changing.

Northern Ethiopia’s year is dominated by two linked rain regimes – spring rains they call “Belg” and summer rains they call “Kiremt.” Belg is critical to the herders, providing the forage for their cattle. Kiremt is critical to the farmers, watering their crops. When Meze-Hausken interviewed residents, she found a widespread belief that there was less rain than there used to be:

The local people gave a clear impression that they have lost one rainy season (Belg) since their fathers’ times. Additionally, they stated the main summer rains have shortened in duration and concluded that some kind of climatic change must be underway.

In response, the farmers have shifted their crops, planting lower-risk varieties that have less yield but are less vulnerable to drought. They plant later and harvest earlier.

But when Meze-Hausken looked at the rainfall records, she found no detectable change in the climate. There is variability, but no significant trend. The year 2002, perceived by some as “the worst in human memory” was actually unexceptional as measured at the rain gauge. So what’s going on?

This is the tricky issue about defining drought, and about understanding more broadly the effect of climate change on human populations.

The droughts in the 1100s and 1200s that led to the collapse of the Anasazi were, in long-term climatologic terms, unexceptional. Earlier human cultures in the region rode out worse. But the Anasazi had taken advantage of favorable climatic conditions to max out the land, growing big and spreading wide. When the drought hit, they had nowhere to turn, no flexibility.

Meze-Hausken describes a similar situation in Ethiopia. Population tripled between 1960 and 2000. People need more food, and they’ve spread out onto marginal land, with the result that per-acre food output has declined. In addition, many farmers migrated into the North Afar area during an unusually wet period in the 1950s and ’60s:

They started to plant maize, sorghum and teff as they used to in their former homesteads in the highlands. At that time people may not have taken into consideration that these rainfall conditions were exceptionally good.

So it may not be that “drought” for these people means “less precipitation than average.” It really seems to mean “less precipitation than we need.”

1. Meze-Hausken, E. (2004) Climate Research 27, 19-31.
2. Glantz, M. H. (2003) Climate affairs : a primer (Island Press, Washington, DC).