Also, the usual rule of thumb: "drones". Flying means constantly expending energy to fight against gravity. Unless the particular problem solved requires flying (to e.g. reach otherwise unreachable spots), solutions involving flying machines are almost always bad. And I don't see anything in reforestation that requires flying.
This is doubly important if you're trying to make the world a better place, instead of just making a quick buck. If all you care about is money, you can make it so that someone else pays the energy costs. But if you truly care about doing something good, then you have to factor them in (they almost always involve non-renewable sources and pollution) and ask yourself, if your plan is even a net improvement for the world.
These kinds of projects remind me of Juicero, where it combines a few things western (middle/upper class?) people care about with technology and expects a great result but end up a middling disappointment.
A ground based drone — eg a modified bulldozer — can carry far more plants as cargo, meaning planting a field of a thousand sapling might require one trip where a flying drone will require a thousand trips.
The only catch is access: for a remote region with no trails of any kind it might be difficult for a large vehicle to navigate through the forest. In this case clearing a path for the planting machine might be a lower cost to the environment than the energy required to fly a thousand sorties with flying planters. A ground based drone will also be able to plant more robust saplings, since payload weight is far less of a concern.
Does anyone know of good places to find opportunities to work on projects like this one?
The downside is that environmental concerns are largely considered a cost for civil engineering projects so much of your work will involve putting together models the 'prove' that the project under consideration will have a low environmental impact. But occasionally you will get a chance to work on a more 'positive' project as well. Either way it's probably a good place to start and to get experience with the realities of the field.
Reading about deploying a swarm of drones to make this planet a better place makes me restore a bit more faith over human kind.