Kirk here. The two most interesting takeaways from the article for me were:

(1) the grasslands of Aso support unique species
(2) grasslands can be better than forests at recharging aquifers

In regard to the second point, while forests are excellent at preventing runoff, they tend to use more of the water, which ultimately returns to the atmosphere through evaporation and transpiration from the leaves of the trees. Grasslands, however, are somewhat more susceptible to runoff in heavy rain, but since they use less water, more of it can seep into the ground to recharge the aquifer.

And, to maintain this ecosystem, the grasslands need to be maintained by controlled burns in the spring.