Building the wall that Donald Trump has ordered on January 25th, as one of his first actions as US president, will put on risk more than 50 animal species that share the ecosystem along the border between the United States and Mexico, scientists from various countries have warned. Since 2006, 1,100 kilometers of barriers covering more than 30 per cent of the border between the countries have been built. The newest executive order commands the “immediate construction of a physical wall”, stating that ‘wall’ means “a physical barrier, continuous and impassable”.