Senior Researcher of Research Center for Mitigasi, Kebencanaan dan Perubahan Iklim (MKPI) ITS, Dr Ir Amien Widodo MSi

ITS Campus, ITS News – Mountain forest ecosystems are not only important for the flora and fauna that inhabit this habitat but also this ecosystem can protect humans from various natural disasters. Seeing this topic, a lecturer at the Sepuluh Nopember Institute of Technology (ITS) examined the effect of changes in mountainous forest land use on land stability in mountainous areas, and recommended the restoration of this land use.

The lecturer who is also a senior researcher from the Research Center for Mitigasi, Kebencanaan dan Perubahan Iklim (MKPI) ITS Dr. Ir Amien Widodo MSi explained, the cutting downs on mountain forests which also occurred in protected areas will disturb the ecosystem of the forest area regardless of its legal status or not. “This has been happening for decades, such as its transformation into tourist areas, hotels, villas, modern settlements, and dense settlements,” he explained.

One of the consequences of this change in land use, he continued, is the disruption of the stability of the mountain soil which has turned critical and is vulnerable to landslides. This happens because the stability of the mountain soil itself is very dependent on the climate and trees. Mountain soils, forests, and climate together will form a symbiotic mutualism in one native forest ecosystem. “You can imagine if one of these factors were removed,” said Amien

The lecturer at the ITS Geophysical Engineering Department also explained the role of trees in mountain soil stability. Mountain soil itself is formed from the weathering of rocks caused by tree roots. The tree will continue to try to find soil mineral nutrients through its roots, which end in releasing enzymes to decompose rocks.

As time goes by, the trees will get bigger and the roots will get longer. Eventually, the land would become thick and the forest would become thick covering the whole mountain. “This thick mountain soil can be stable on sharp slopes because it is held back by the roots of forest fibers, while the supporting roots will function as an anchor to the soil layer underneath,” he added.

In the forest, leaves and tree branches that fall to the forest floor form a thick layer of litter that goes to the ground through the litter layer which eventually seeps into the ground, filling the underground water reserves. Forests in mountains are able to absorb 80 percent of annual rainwater as deep as the ground, and a small proportion of rainwater is distributed as surface water around the mountain as springs. “This water source will supply and increase the flow of river water around the mountain,” said Amien.

Seeing the important role of trees in the stability of mountain soils and their ecosystems, Amien said that changes in mountain land use could have fatal consequences. The replacement of native forest in the mountains into a tourist area can leave the mountain soil unprotected and unstable. The land of the mountains is finally ready for landslides and is only waiting for triggers such as rain and / or earthquakes.

The satellite picture of an area in Sumedang in which landslides occurred due to a forest that has undergone land-use changes

Without any trees around, cracks will appear in the dry land that will widen. When the rainy season comes, rainwater will flow and some of it will absorb the cracks of the slope, so that the slope soil gets heavier and starts moving, indicated by the presence of subsidence

Rainwater that seeps into the soil will reduce the binding capacity (cohesion) of the soil so that the slopes will slide like a liquid. “This landslide will bring down whatever is on it, such as large stones, trees, logs, or even houses,” said the lecturer who is actively researching this disaster.

That is why Amien really hopes for government actions to restore the function of the mountain forest area considering that many have changed their function. According to him, now many mountainous areas have become private property, officials, and developers. “The government must be firm in restoring the function of the area as a forest area that functions as protection and absorption,” he reminded. (ri/nadh/ ITS Public Relations)