Encroachment is primarily happening in the west block, and is carried out almost exclusively by in-migrants.
There is also a latent threat from bad land use planning, such as the inappropriate classification of forests, and planned road developments. One logging company (PT Teluk Nauli) in the past received a logging concession of 30,500 ha in the west forest block. The concession lies in the upper catchments of all the major watersheds in the west block, including the Sipansihaporas catchment that feeds the hydrolectric plant. An independent consultant’s report to the Ministry of Forestry recommended that this concessioon should not be logged because of the high susceptibility of the area to erosion meaning that environmental and economic costs would be high, while the stock of commercially valuable timber was relatively low.