Leuser Ecosystem, Indonesia: Using Drones for Forest Monitoring

Drone image of a restoration area in the Leuser Ecosystem. Drone images like this can help conservation managers monitor the progress of restoration and the scale of the initial damage.

There's just one place left on earth where tigers, elephants, orangutans, and rhinos live together in the wild: the Leuser Ecosystem World Heritage Site on the Indonesian island of Sumatra.

One of the last remaining intact rainforests in all of Indonesia, the Leuser Ecosystem spans 2.6 million hectares, including lowland and montane rainforests, wetlands, and over 185,000 hectares of carbon-rich peatlands. It is a crucial source of clean drinking water and agricultural livelihoods for over four million people. In fact, the ecosystem services provided by the Leuser Ecosystem, including 1.6 billion tons of carbon and the provision of water to 4 million people, are valued at over US$600 million annually.

The Leuser Ecosystem from the air.

However, Leuser is highly endangered, with threats accelerating since the end of the Acehnese rebellion and civil war. Post-war stability is bringing rapid invasion of commercial interests in palm oil, rubber, and logging, with companies legally and illegally deforesting the Leuser Ecosystem at astounding rates. Between 1985 and 2009, half of Sumatra’s forests were destroyed.

The decimation continues today; despite its protected status, Leuser has lost one-fifth of its lowland forests to illegal commercial activities in just the past five years. At that rate, the forest will be completely destroyed within two decades.

Fires are used to clear forest to make way for illegal palm oil plantations.

The primary threat to this unique ecosystem is illegal palm oil expansion. As global demand for palm oil rises, oil palm growers seek to multiply the acreage of this valuable crop. Unfortunately, there is little unoccupied land left in Indonesia, leading growers to encroach illegally into the country’s dwindling but exceptionally biodiverse protected areas. 

In addition to palm oil, it faces accelerating threats by illegal and commercial interests in logging, mining, ill-advised energy projects, and the fragmentation of forests by new roads. The fires from this widespread destruction have caused major haze pollution from Singapore to Jakarta, resulting in huge economic losses and public health issues. 

A denuded landscape where lush forest once stood.

Due to this destruction, Sumatra’s unique megafauna species are in serious danger. Of the world’s 80 remaining wild Sumatran rhinos, Leuser contains 50—the last viable population of this species on Earth. Of just 400 remaining Sumatran tigers, more than 100 live in Leuser, which is one of only two regions with enough breeding females to sustain this subspecies.

Finally, 85% of the world’s critically endangered Sumatran orangutans call this forest home. As Sumatra’s forests disappear, it becomes increasingly likely that Sumatran orangutans will become the first great ape to go extinct. All of this has led conservationists to call Leuser one of the “world’s most irreplaceable protected areas” – if this forest disappears, these species will go with it. 

A Sumatran rhino, one of just 80 left in the world.

Using Drones for Forest Monitoring

Global Conservation has funded acquisition and deployment of advanced mapping UAVs/drones to document illegal deforestation within and around the Leuser Ecosystem. Both fixed-wing long-distance drones and quadcopters are being used to uncover large-scale rainforest destruction for illegal palm oil plantations within the Gunung Leuser National Park and Greater Leuser Ecosystem.

Because they allow the Leuser team to see large areas of forests far from access roads, drones are proving invaluable in the fight to get government, community leaders and law enforcement to stop forest and wildlife habitat destruction.Drones are relatively cheap, can cover hundreds or even thousands of hectares in a short space of time, and can beam back live video transmission.

A drone pilot in the Leuser maps out a flight plan. Image courtesy HakA.

The Leuser Ecosystem team are currently using drones in three regions of the ecosystem to monitor encroachment and forest loss. They are also conducting high-resolution mapping of illegal logging and forest destruction based on Global Forest Watch fire reporting.

Illegal burning in the Leuser ecosystem, photographed with a drone. Image courtesy HAkA.

Illegal clearing for road development as seen from a drone. Image courtesty HAkA.

While the use of drones for anti-poaching has been less productive, mapping of forest destruction in faraway areas using drones has proven highly effective. Mapping and imagery are used to prepare police cases against illegal loggers, and in discussions with local communities and their leaders to reverse destructive practices. 

Our partners in conservation prepare a drone to fly in the Leuser Ecosystem. Image courtesy Forum Konservasi Leuser.

Using drones, we documented critical orangutan habitat being destroyed within Gunung Leuser National Park. The next step will be the major task of removing illegal palm plantations and finally, reforestation. The team also attempted to use FLIR thermal cameras mounted on drones to identify poacher campfire locations.

An illegal mining camp in the Leuser Ecosystem, found using a drone. Image courtesy HAkA.

Our partners collaborate with police and Forest Management Officers by showing them images and locations of illegal activities that have been detected using drones. The authorities can then intervene. Image courtesy HAkA.

Using Drones for Orangutan Monitoring

There are two species of orangutans alive today, and they are only found in the tropical forests of Indonesia and Malaysia. These highly intelligent apes are among our closest relatives, sharing 97% of our DNA. Unfortunately, both species are highly endangered, due to rampant habitat destruction.

Monitoring orangutan populations in the Leuser Ecosystem is particularly challenging. Traditionally, researchers have estimated orangutan populations by walking line transects through the rainforest and counting orangutan nests. However, their habitat is dense and difficult, requiring significant time and funding. Sometimes, researchers need to cut a path through the dense undergrowth, and they can typically only walk two kilometers of transect per day. With total transect lengths reaching 100km or more, research teams often spend the better part of a month conducting one survey.

Methods that are often used to estimate populations of ground-dwelling species aren’t of much use; because orangutans move through the trees in threedimensional space, camera traps are unlikely to capture them. Due to these challenges, researchers have been unable to conduct population counts at a high enough frequency to accurately monitor changes.

An illegally cleared area of the Leuser Ecosystem, as seen from a drone. These clearings are directly threatening orangutan survival. Image courtesy HAkA.

 An illegal palm plantation detected by a drone, built in an area that was illegally cleared. Image courtesy HAkA.

Researchers at Conservation Drones figured out that unmanned aerial vehicles (UAVs) could address this problem. By flying fixed-wing UAVs in a pre-programmed pattern above the forest, researchers could capture thousands of high-resolution images of the forest canopy. They could then scour these images for orangutan nests, producing an accurate count of the number of nests in a given area. Although these nests must currently be counted manually, researchers are working on training artificial intelligence to detect nests in the images. 

Orangutan nest as seen from a drone. Image courtesy of Orangutan Nest Watch.

Researchers chose fixed-wing UAVs because they are faster than quadcopters and can fly further on a single battery. Even though fixed-wing UAV surveys are faster and cheaper than walking transects, able to fly 50km in 40 minutes, they tend to differ from foot-transect surveys in how many nests they detect. Therefore, the first step to implementing this new technology was to conduct both survey types in the same area and then compare the results. After doing this enough times, researchers were able to calculate the error and accurately estimate populations using UAV surveys alone.

Orangutans (left) and proboscis monkeys (right) have unique heat signatures, allowing researchers to count them using thermal cameras mounted on drones. Images courtesy of Liverpool John Moores University and WWF.

Most recently, researchers have begun to add thermal cameras to the drones, helping them to detect orangutans even more reliably using their heat signatures. This new method adds to the many uses of UAVs in conservation, including mapping land use types and forest cover, and anti-poaching.

You can read more about our use of drones for Global Park Defense here.

The Forum Konservasi Leuser team with their fixed-wing drone.