Learn French: Le reboisement ne réussit jamais sans davantage de biodiversité. - Reforestation never succeeds without more biodiversity.

Yes, they are completely interchangeable here. Both mean "more biodiversity". The word davantage is just slightly more formal or elevated than plus, which is why you often see it in texts about topics like science, politics, or the environment.

Is it possible to drop the de and just say davantage biodiversité?

No. Whenever you use davantage to express a quantity of a noun, you must use de, just like you do with plus de or beaucoup de. You can only use davantage on its own when it modifies a verb, for example: Il faut planter davantage (We need to plant more).

Why is there no pas in the negative phrase ne réussit jamais?

In French, specific negative words like jamais (never), rien (nothing), and personne (nobody) take the place of pas. Using both together is incorrect. The standard structure simply surrounds the conjugated verb: ne + [verb] + jamais.

I don't recognize the word reboisement. Is there an easy way to break it down?

Look closely at the middle of the word: it contains bois, which means "wood" or "forest". When combined with the prefix re- (again) and the suffix -ement (which turns an action into a noun), it literally means the act of "re-wooding" or reforestation.