Ndiamaguene, SENEGAL — I am visiting Ndiamaguene village in the far northwest of Senegal. If I were giving you directions I’d tell you that it’s the last stop after the last stop — it’s the village after the highway ends, after the paved road ends, after the gravel road ends and after the desert track ends. Turn left at the last baobab tree.

It’s worth the trek, though, if you’re looking for the headwaters of the immigration flood now flowing from Africa to Europe via Libya. It starts here.

It begins with a trickle of migrants from a thousand little villages and towns across West Africa like Ndiamaguene, a five-hour drive from the capital, Dakar. I visited with a team working on the documentary “Years of Living Dangerously,” about the connection between climate change and human migration, which will appear this fall on the National Geographic Channel. The day we came, April 14, it was 113 degrees — far above the historical average for the day, a crazy level of extreme weather.

But there is an even bigger abnormality in Ndiamaguene, a farming village of mud-brick homes and thatch-roof huts. The village chief gathered virtually everyone in his community to receive us, and they formed a welcoming circle of women in colorful prints and cheerful boys and girls with incandescent smiles, home from school for lunch. But the second you sit down with them you realize that something is wrong with this picture.

There are almost no young or middle-aged men in this village of 300. They’re gone.

It wasn’t disease. They’ve all hit the road. The village’s climate-hammered farmlands can no longer sustain them, and with so many kids — 42 percent of Senegal’s population is under 14 years old — there are too many mouths to feed from the declining yields. So the men have scattered to the four winds in search of any job that will pay them enough to live on and send some money back to their wives or parents.