Reforestation is a long and complex process. It requires way more than simply planting trees. A whole new ecosytem needs to be created so that the trees will grow healthy and strong. Maintenance is an extremely important part of tropical restoration. During several years after the plantation of new trees, specialists continue to take care of the trees as they grow into mature forest. Such supervision includes controlling leaf-cutter ants and ferns that can shade out young trees, and fertilizing very poor soils by planting herbs that naturally contribute fertilizing nitrogen to the soil.