The invasion of Cogon Grass (Imperata cylindrica) in deforestation areas within Indonesia


The deforestation rate in Indonesia is the highest in the world, even “exceeded” Brazil. Deforestation in Indonesia provides suitable conditions for invasion of cogon grass, a fast growing weed species. Cogon grass is a perennial grass species that can adapt to poor soil condition. Because it has rhizomes (lateral, adventitious root). The species can live in wide range of habitat, from natural forest to disturbed forest, urban land, wetland, planted land, riparian. Cogon grass is a native species in Japan, Philippines and Thailand. This species has now spreads across the world, except Antarctica and thus classified as weed. The ability of the weed to grow faster is a threat for native plant species. In addition, the weed also has an allopathic effect other seedling.

Cogon grass (or alang-alang, in Indonesian) occupies 8.6 million ha of Indonesia’s grassland. The spread of the weed in Indonesia is across the country, particularly in Sumatera and Kalimantan Island where the deforestation rate is high. wri15_global_brazil_indonesia-01

Annual tree cover loss in Brazil and Indonesia from 2001 to 2014.


The rate of deforestation in Indonesian from 2000-2010 distinguished by island.

The conversion of primary forest to grassland makes the land more prone to fire. Land management of grasslands should combine technical, chemical and biological practices to suppress the weed’s growth. Mowing the grass along with herbicide is effective to depress the grass growth and provide opportunities for other seedlings to regrow. However, the use of chemicals such as herbicides to suppress weed should consider the season. The application of chemicals in rainy season is not effective because will be washed by the rain water and can contaminate water catchment. An alternative way to suppress the weed’s growth is by using other fast-growing exotic plants. Brown salwood (Acacia mangium), gamhar (Gmelina arborea) and batai wood (Paraserinthes falcataria) can reduce the invasion of cogon grass in deforested area. Although those trees species are exotic, they can provide litter to the soil as fertilizer and shade for another seed to regrow. Cogon grass is a light intolerant species and provide shading to the weed can reduce their invasive characteristics.  

Conversion of grassland back to forested land is crucial for several reason. The first reason is to reduce fire event in deforested area. The grassland gives a patches for the fire to spread further. Reforestation of grassland will provide dense tropical storey that more robust to fire event. The second reason is to restore habitat for native species. Grassland that dominated by one plant species does not provide diverse food supply for the fauna. Hence, the biodiversity in cogon grass grassland is depleted than in forested area. The third reason is grassland has a higher albedo than forested area. It means grassland reflects back more solar radiation to the atmosphere that will increase atmosphere temperature. A shift of landscape from forested area to grassland means larger area of reflect the solar radiation to the atmosphere.

The expansion of cogon grass can be prevented through reform of regulations or policies regarding deforestation in Indonesia. The latest government regulation regarding minimize deforestation is extending the moratorium on new forest concession. In other words, there will be no permits issued to new land clearing in forested area. However, the regulation allows land clearing in primary forest and peatland for geothermal, oil mining, electricity network, paddy fields and sugarcane activities. On other hand, from environmentalist perspective, the moratorium is not effective to tackle deforestation in Indonesia. This is because some plantations still can burn or make paved road in forested areas. The fundamental problems in managing forest in Indonesia is the overlapping of forest boundary. A different perspective of the plantations and the governments about the boundary of concession area and forested land is caused by different maps about their authority. Fortunately, there is an effort to publish one integrative map that should be used by both the government and plantations in future.

Another cause of deforestation is come from business “tricks”. There are some plantations that already got concession for their activity do not planting all of the land because of financial problems or they just aim to cut the logs and left the site after that. The left land then become occupied by peasant or local people as small plantation or agriculture site. The lack of monitoring plantations activities in the field and a corruption is the biggest problem in Indonesia’s forestry. For example, slash and burn practice that commonly do by plantations resulted haze problems routinely every year in some part of the country. Even, the uncontrolled burn not only causes environmental degradation but also affect local people’s health and economy loss.

In conclusion, deforestation in Indonesia is one of “wicked” problem along with corruption. And the expansion of cogon grass in deforestation area is one proof of environmental degradation in Indonesia.

                                                                                                                        (Siti Wahyuningsih/ U5938459)



About Biodiversity Conservation Blog

I am an Associate Professor at The Australian National University and convene a (very awesome) course called Biodiversity Conservation. Myself and students in the course contribute to this blog.
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One Response to The invasion of Cogon Grass (Imperata cylindrica) in deforestation areas within Indonesia

  1. Thanks for the interesting links between land clearing and cogon grass Siti. Phil

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