To get started you will need to at least coordinate with several types of people/groups. Depending on the project, one person may have several roles at once, but it is rare to have all of them, so surely a drone reforestation project is a team project:
Local native seed suppliers - where do we get the seeds?
Without seeds there are no trees, so you will need to locate a supplier of native seeds, taken from the closest place to the reforestation area, who can supply you with the quantity (we are not talking about dozens of seeds, but thousands), quality, and schedule you have determined. You can also coordinate a group of local volunteers and collect wild seeds in a sustainable way, this is only one part of not depleting the natural seed bank.
Biologists/Foresters Which species and where to plant each one?
Each ecosystem has its own characteristics, so knowledge is needed before any transformation of the territory (we want to repair ecosystems, not degrade them). Normally we should choose the closest functional reference ecosystem and copy its species.
Seed enhacers: Who will treat the seeds?
Seeds need to be pelletised to increase survival in aerial plantings, a committed person is required who will be trained in this work.
Drone pilots - who will build/fly the drone?
Ideally, years of previous drone piloting experience are required before flying a cargo drone, due to its size and dangerousness. Under no circumstances should such a drone be a pilot’s first drone. They should be pilots who also know some hardware for repairs, but who have previously flown drones with flight boards such as Pixhawk, Ardupilot or PX4.
Land owner: Where is the land to be planted?
Not only do you have to find this territory, but you should also guarantee, usually through a contract, that the trees will remain there for as long as you consider appropriate, so that the owner does not change his mind and wants to use the territory for a different purpose and wants to cut them down prematurely.
Who will pay for all the work?
We will need money to do all this, even if you have the drone and all the will in the world, it takes a lot of work and energy to organise everything, it’s fine if it’s a non-profit project, but it must be economically sustainable.
Now, where to start? This will depend above all on what your speciality would be, what would be your strengths and what would be your weaknesses. There are projects that would start by looking for money, other projects would start by looking for equipment, and others would first look at how to treat the seeds to first test the viability of aerial seeding for those species in those ecosystems.