Osman Ali grew up near southern Somalia’s Shabelle river that was once deep enough for him to dive in for a swim. But in the last three years, droughts have thinned it into a dirty stream. After his sheep and goats were reduced to skin and bones and his corn and sesame crops wilted in the fields, he was left at the mercy of armed extortionists he couldn’t pay. The 29-year-old sold his family’s land and bought a ticket to Brazil. A two-month-long trudge through jungles, rivers and cities brought him to Tapachula in Mexico, with hopes of heading to the U.S.' southern border.

Like him, Ibrahima Coulibaly was in Tapachula, hanging around in the sweltering heat on a sidewalk outside the city’s immigration office in a yellow Lakers basketball jersey. He left his home near Tambacounda in eastern Senegal when he could no longer farm his five-acre plot of land. A series of droughts destroyed his millet, peanut and bean crops, leaving his family with little to eat and prompting him to sell his 32 head of cattle and embark on a long journey to the Americas.

Arriving in Brazil earlier this year and robbed in the Darien Gap — the dense jungle between Colombia and Panama infested with poisonous snakes and bandits — he waited desperately for a permit to continue crossing Mexico to get to the U.S. border.