Why is the planet becoming more green over the past three decades (per NASA observations) if there's a net loss?

You are well into 'just asking questions'[1] territory, something that really ticks me off because all of these are a google search away, but just for the record:

Replanting and more (and more intense) agriculture is what is making our planet greener. For the moment. But there are pretty clear upper limits to what the planet can deal with temperature wise, at some point it will get so hot that plants will not be able to retain their moisture. Already there are territories that were arable in the recent past that today are not or are subject to extreme droughts almost every summer.

For Europe the estimates are that Portugal (and Spain) are going to be the first to be hit really hard, and in a way that is already underway:

https://portuguese-american-journal.com/wildfires-severe-cli...

[1] https://rationalwiki.org/wiki/Just_asking_questions

Also the planet could well become greener with global warming but the issue is the rate of change. Even if the new growing conditions were great for some crops, evolving our entire agriculture and food regimen to them in a few decades is a huge ordeal.