Sometimes, resources don't decrease but instead increase, as is the case in the mod Factorio and Conquer: Tiberian Dawn. Its resource, Green Tiberium, grows over time, so players need to manage its quantity to ensure it's neither too scarce nor too abundant.
Therefore, I suggest adding a threshold for resource increase, which would trigger a reminder once it exceeds that value.
a threshold on resource increase, do you mean on the speed of increase or some derivative value?
Based on the current lower threshold, I suggest adding an optional upper limit.
For instance, the current total quantity of Green Tiberium is 10M, and a reminder will be triggered when it drops below 20% (2M) or surpasses 200% (20M). Of course, the values can be tailored to your preferences.