A world of walls

A more and more interconnected world is raising walls and fences to keep out those it considers undesirable. The number of physical barriers that existed in 2001 was 17: the figure has presently jumped up to 70*. /n/n Some of them reinforce borders. Others divide the same population. Some seek to stop the refugee flow. Others hide poverty. Or fear. Or war. Or inequality. Or climate change. /n/n Folha went to four different continents to uncover what - and who - lies behind them.