निम्नलिखित में से किसे जलसंभर प्रबंधन (वॉटरशेड मैनेजमेंट) की एक प्रमुख चुनौती या हानि माना जाता है?

Prolonged exposure to extreme cold temperatures may result in tissue damage known as frostbite, which is categorized as a:

In the context of ecosystem energy dynamics, which of the following expressions correctly defines Net Primary Productivity (NPP)?