Furthermore, several areas in which the slopes appear not so steep using the standard methodology, in fact have a very rugged micro-topography with main steep albeit short slopes.
As an example, looking at a page from the book that accompanies the soil map for the Sibolga-Padang Sidempuan area (Buku Keterangan Peta Satuan Lahan dan Tanah Lembar Sibolga dan Padang Sidempuan), published by the Indonesian soil research institute, describe an area that nominally has slopes of only 8 – 16% as extremely dissected (i.e. many rivers with steep sides) and extensive erosion.
In view of the fact that the Batang Toru forests area extremely important in maintaining the hydrological functions of several rivers systems that are important both for local people and downstream industries, it is clear that the forest function planning must incorporate all aspects of environmental sensitivity. It is worth learning from previous generations: many of the villages around the Batang Toru forests are very old, and they have not expanded into the surrounding forests because they have understood that opening these forests would cause damaging environmental consequences.