Full coverage: 80th Anniversary of the Victory of the Red Army's Long March

In this episode, we travel to the Zoige Marsh in southwest China's Sichuan province. Here, 80 years ago during the long march, besides hunger, coldness and disease, the troops had one more adversary to fight - the deadly swamps. Now 80 years later, the wetland here is facing an existential threat.

This was once a deadly marsh for Red Army soldiers. Now the boggy waters are gone, and the grassland deteriorating. Drolma X keeps far fewer yaks than his family of six is allowed under a community-imposed quota.

There isn't enough grass for the yaks to eat. So I voluntarily cut down the number of my yaks.

The Zoige Marsh lies on the northeastern edge of the Tibetan Plateau. It influences local weather, and provides water that flows into the upper reaches of the Yellow River. The culprits behind its decline -- a large-scale water draining project in the 1960s to make way for animal husbandry, along with overgrazing and global warming.

In the most extreme case - desertification. It’s hard to imagine that this is happening right in the middle of vast grasslands. And this is not a single case. Standing here you can see the same phenomenon happening over there on that hillside.

The local government is stepping up efforts to cope. This area called Flower Lake demonstrates what can be achieved. This dam was built near the lake, to retain water, and keep a steady supply for the surrounding wetland.

Since the dam was built, the size of the lake has expanded three times over, and the water level has risen by 52 centimeters. It’s a successful model, but can it be replicated?

Han Jinfeng is with the local wetland restoration office. 

"No. Other places aren't the same. The model only succeeded here because the lake happens to be here to provide water. Other places don't have this luxury," Han Jsaid.

Smaller-scale dams are being built all across the wetlands... with limited results. But perhaps the biggest difference now is the strong will among China's top leaders to put nature ahead of economic development.

Officials here admit that change is going to be slow. But that's what these Tibetan herdsmen, and their centuries-old ways are counting on.