Baselinestudy Guide Biodiversity & Carbon Stock

I want to help a small association to acess Biodiversity Conservation & Carbon Fixation Credits from foreign donors.
What is the current state of the art for minimum baseline data ? How far are species richness and relative abundance for plants, animals & insects relevant or not? Looks to me like most of the data is about analysing participants and automated satelite image landuse analysis…
Can you recomend some field guides?
Thanks in advance