Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

Thousands of heavy-duty trucks loaded with coal are lined up for up to 130 kilometres from the Mongolia-China border on a sole road in the Gobi desert, Mongolia, October 29, 2017. The journey can take more than a week. (Photo by Bazarsukh Rentsendorj/Reuters)

People walk to the Venezuela Aid Live concert that will play on the Colombian side of the border near the Simon Bolivar International Bridge, from San Antonio del Tachira, Venezuela, Friday, February 22, 2019. (Photo by Rodrigo Abd/AP Photo)

Colombian police help carry people's household belongings across the Tachira River from Venezuela, top, to Colombia, on the border that separates San Antonio del Tachira, Venezuela from Villa del Rosario, Colombia, Tuesday, August 25, 2015, during a mass exodus of Colombians. Venezuelan President Nicolas Maduro vowed to extend a crackdown on illegal migrants from neighboring Colombia he blames for rampant crime and widespread shortages, while authorities across the border struggled to attend to droves of returning deportees. (Photo by Eliecer Mantilla/AP Photo)

A Syrian refugee girl covers herself with a blanket as she stands outside tents at a makeshift settlement in Bar Elias in the Bekaa valley January 5, 2015. Lebanon enforced new immigration controls at the Syrian border on Monday in a move to gain control of the steady stream of refugees from its much larger neighbour. (Photo by Mohamed Azakir/Reuters)

India's Border Security Force (BSF) “Daredevils” motorcycle riders perform during a rehearsal for the Republic Day parade on a foggy winter morning in New Delhi January 8, 2015. India will celebrate its annual Republic Day on January 26. (Photo by Ahmad Masood/Reuters)

Alluvial Fan, China. A vast alluvial fan blossoms across the desolate landscape between the Kunlun and Altun mountain ranges that form the southern border of the Taklimakan Desert in China’s XinJiang Province. Image taken by the ASTER instrument on NASA’s Terra satellite on May 2nd, 2002. (Photo by NASA/GSFC/USGS EROS Data Center)

The Tsaatan people are one of the world’s last groups of nomadic reindeer herders and they live in Khövsgöl Aimag in northern Mongolia. They are originally from across the border in what is now the Tuva republic of Russia. (Photo by Pascal Mannaerts/Rex Feature/Shutterstock)