Variety of Land Usage - Terrace

I witnessed the degradation of terraced fields during our fieldwork. 

The video was shot one morning before the rainy season, when I followed "uncle" to check the water level in his terraced fields. He told me that these fields had been cultivated by his family for over a hundred years. But now they're growing a new type of millet supplied by the state, with a higher yield than traditional millet. 
 
The farmers used to cut down the woods surrounding these fields and stopped the cutting twenty years ago. These woods have now become a patch of forest, but the terraced fields are losing the moisture in their soil. He pointed out the land close to this forest and told me that this land was also used to grow paddy, but now they can only grow corn, which doesn't need as much water. 

I understand that there is tension between the terrace and the forest here, but I also wonder if there are other reasons for the decrease in soil moisture, whether we can pay attention to the requirement for a new, higher-yielding paddy or to climate change? 
 
This year, the spring rains weren't enough for these terraces, so the villagers had to repair the water pipe and bring in water from the other side of the mountain. Some villagers have stated that the mining operations underneath the village are also extracting water from the mountain, in short, various elements are contributing to land degradation.