How do reforestation and reclamation positively impact land?
The goal of reforestation is to restore an area to its previous, natural state.
The goal of reforestation is to restore an area to its previous, natural state. This can also be called "rewilding" but the goal is the same: return an ecosystem or a landscape to its previous state before humans became involved.
Benefits include restoring natural habitat, which can protect against invasive species and support native wildlife. Soil erosion processes and soil health may return to normal, especially if an area goes from a mainly urban area to one with vegetation. Trees are also carbon dioxide sinks, thus adding more of them removes some of the damage humans have caused burning fossil fuels.
This sounds relatively straightforward, but it's actually quite a complicated process. Sometimes we don't know exactly what the area would have looked like before humans arrived. Or reforestation doesn't take into account that nature and the land changes naturally over time.
For example, we may think returning a few blocks of parking lot to a forest is the right thing to do, because that is the last natural landscape we have a recording of existing in that spot. However, perhaps that area of land that has been an industrial area/paved area for the past 80 years would actually have progressed into landscape that resembled more of a grassland, had it been unaltered by humans.
Note : Land reclamation can refer to the process of making new land in area that previously was an ocean, a river, and so forth. This does not have the positive effects you may think of in terms of reclaiming the land. Thus, the context and where this term is being used is important. If used to describe the process of returning an area to its undisturbed state (something natural but not necessarily a forest), then the positive effects will be similar to the ones mentioned above.