Out of Africa, Once More

The migration that brought modern humans across the Red Sea from Africa some 60,000 years ago reflected growing pressure on resources in Africa, driven by “rapid” population growth.

Of course back then, rapid population growth proceeded at perhaps a tenth of one percent per year, and “rapid” change occurred over a few thousand years.

Nor did the migration out of Africa have a noticeable effect on population within Africa. It is likely that the descendants of only a handful of African emigrants populated the entire rest of the world over the next 30,000 years.

As humans gradually spread over the Middle East, South Asia, Australia, North Asia, Europe and the Americas, they responded to opportunity. When the Sahara bloomed, people hunted and gathered food there. As the Sahara turned to desert, they moved southward and northward.

When the sea fell, its water sequestered in ice sheets, and humans took advantage of land bridges and moved onward to find new hospitable territories. When ice ages ended, people once again migrated toward the poles.

Today, time moves faster. In the roughly 60,000 years from when modern humans emerged until 1800, the population grew to perhaps one billion. Over the next 200 years, it grew to six billion.

The global climate changes that drive human migration have accelerated, too. Changes in temperature and rainfall patterns now threaten to take place over decades, not centuries or millennia.

But the consequences of today’s environmental pressures are likely to be broadly similar to those of ancient times: People will leave places that no longer offer a livelihood to find more hospitable lands.

Disturbingly, large parts of Africa — the poorest part of the world — loom among the regions most threatened by climate change. Areas that today are semi-arid but relatively densely populated — the Sahel, much of East Africa and large parts of Zimbabwe, Mozambique and Angola — are likely to lose the capacity to support agricultural or even pastoral populations.

Indeed, the International Panel on Climate Change reports that 10-30% of today’s population of Africa faces water shortages.

Today, about 35% of the population of sub-Saharan Africa lives in urban areas. How fast can this change? Where will people go? They will move to cities, to cultivatable parts of national parks, and to any other places they think they might be able to scratch out a living.

Many will find their way onto buses and boats that give them a shot at reaching North Africa and Europe. Depending on how fast climate change proceeds, this could result in steady but urgent pressure on the North. Or the droughts in rainfall could undam a human flood.

These victims of climate change have played no role in its genesis. They probably produce fewer greenhouse gases over a lifetime than a citizen of Northern Europe or North America produces in a month.

The family driven from its farm in central Kenya will know that drought and unreliable rainfall have made it impossible to survive in Kitui, but they will have no idea of the role that central heating in Norway, SUVs in Illinois or new factories in Beijing play in their suffering.

It is very likely, though, that as the megalopolises of Africa fill with ever more desperate migrants, conditions once again will drive people across the sea in search of food and shelter.

These migrants will leave not at the rate of dozens per millennium. Rather, they are likely to move in the hundreds of thousands per year.

As with almost every aspect of climate change, we can invest now — or we can wait and see if dire predictions play out. Surely, everyone stands to gain by keeping Kenya and Sudan and Nigeria livable. This benefits all of us — not just the poor Africans who must watch the sky and then watch their millet die before it can ripen.