The unseen driver behind the migrant caravan: climate change

While violence and poverty have been cited as the reasons for the exodus, experts say the big picture is that changing climate is forcing farmers off their land - and it's likely to get worse

Thousands of Central American migrants trudging through Mexico towards the US have regularly been described as either fleeing gang violence or extreme poverty.

But another crucial driving factor behind the migrant caravan has been harder to grasp: climate change.