When you travel north in Ghana, the climate becomes drier and the villages poorer, until you end up in the Upper East and Upper West regions - friendly, slow-moving places, dry for most of the year and becoming more so. In other words, exactly the sorts of places where you would expect climate change-related migration to begin.
Sam Knight in the Financial Times tries to unpick the climate change migration debate. Is climate change migration something entirely new, or merely a continuation of existing trends? It looks like the numbers will be greater than we have been used (the Stern review suggests anything between 200 and 500 million people over the next 50 years), but that doesn't mean that starving farmers from Burkina Faso or Bangladesh will be pitching up in European capitals. More likely, the children of the rural poor will migrate to coastal cities and the educated youth of the capitals will migrate to richer countries, as they do now.
So what can we do about it? Beyond the obvious priority of containing climate change, I can think of two helpful policies:
1. Invest in agriculture in vulnerable areas - whether it's drought-resistant seeds, irrigation, new kinds of crops that reduce soil erosion or thrive in drier (or more volatile) climates
2. Improve transport links between coastal and inland regions: that facilitates seasonal migration, which keeps remote areas alive through remittances and periodic visits. It will also bring down the cost of living and make it easier for people in the arid areas to sell whatever they grow to richer urban consumers
On the other hand, these two are unlikely to work:
1. Trying to restrict migration - through passports, ID cards, quotas, . People will still move, only they will pay more for it and people traffickers will collect the difference
2. Bribing people to stay at home through welfare payments, social services, etc. Investing in health and education in rural areas is a great area, but it's more likely to promote migration than discourage it
Climate-induced migration is nothing new: we've been at it since the Sahara was green. It may be that the last few millennia were the abnormality and human migration patterns will end up looking more like they did before we invented agriculture.