Salva, in the modern day, talking about challenges in nature he encountered on his journey out of Sudan.
When fleeing Sudan I faced many challenges and I found that nature can present many challenges toward humans.
Water For South Sudan
"Every movement in the grass was a lion stalking, every stillness a lion waiting to spring. Marial was gone-vanished into the night. He would never have wandered away from the group on his own. HIs disappearance could only mean one thing. Lion."
Salva: Uncle and I walked together through lion country with little food.
"Not one fishermen stayed to talk or eat more or do anything else. It was almost as if they all vanished at the same moment. ONly a few minutes later, mosquitoes rose up from the water, from the reeds, from everywhere. Huge dark clouds of them appeared, their high-pitched whine fulling the air. Thousands, maybe millions, of hungry mosquitoes massed so thickly that in one breath Salva could have ended up with a mouthful of he wasn't careful. And even if he was, they were everywhere-in his eyes, nose, ears, on every part of his body."
Salva: On our way across the Nile, we spent the night on an island. As the evening crept away, mosquitos swarmed the island. I got barely in sleep as mosquitoes bit my skin.
Salva: I had to walk through the rough, dry terrain of the Akobo desert with little water.
"The first day in the desert felt like the longest day Salva ever lived through. The sun was relentless and eternal: There was neither a wisp of cloud nor whiff of breeze for relief." 
Salva: I had to walk a long distances everyday to flee the Sudanese Civil War.
Nature can present many challenges towards humans and the challenges can be grueling and tough.