Radar satellite exposes illegal logging in African rainforests

Wageningen Climate Solutions

Image: Axel FassioCIFOR

By Francine Wildenborg - January 2021

Forest elephants wander along the banks of the Congo River, watched over by mountain gorillas from the trees. For now, at least. Because the African rainforest is shrinking day by day as a result of illegal deforestation. WUR helps to stop that with its new alerting system, which shows exactly where trees are being logged.

Visitors to the RADD (RAdar for Detecting Deforestation) alert app might initially think they’re on Google Maps. But there’s one big difference. This is no ordinary map: it's an alerting system for deforestation. If you zoom into the southern part of the Central African Republic, around 50 km south-east of the town of Berbérati you’ll see red patches, some straight ones which are roads, and smaller patches around them.

“That’s where forest has recently been logged,” says Johannes Reiche, associate professor of Radar remote sensing. Reiche’s team uses publicly available radar images gathered every six to twelve days by the European Space Agency’s Sentinel-1 satellite. If areas of rainforest disappear, a ‘deforestation alert’ is triggered and it is marked in red. This enables local enforcement agencies to intervene much more quickly and precisely to stop illegal logging.

Wageningen’s RADD alerting system covers the entire African rainforest. Most of it lies within the Congo Basin: the area along the Congo River, which meanders through countries such as the Democratic Republic of the Congo, Gabon, Cameroon and the Central African Republic. The Congo Basin is the second largest tropical rainforest in the world, after the Amazon, and is home to countless plant and animal species, some of them endangered. But every year at least 800,000 hectares of forest disappear, equivalent to one-fifth of the Netherlands.

The RADD alerting system reveals deforestation caused by selective logging: logging roads with tree canopy gaps in the rainforest alongside them. Image: Johannes Reiche

Radar technology

According to Reiche, existing alerting systems rely mostly on optical images: regular satellite photos of the Earth. “You often wouldn't see anything on these for months, because there would be thick cloud cover above the African rainforest, particularly during the rainy season. Countries like the Congo and Gabon have some of the heaviest cloud coverage in the world.” This meant that illegal logging used to go unnoticed for months, by which time it was too late to intervene.

“The high-resolution radar images produced by Sentinel-1 allow us to look straight through the clouds, 365 days a year,” explains Reiche enthusiastically. Last year he trialled the RADD system in a smaller region: Indonesia, where rainforest is being cleared for palm oil plantations. Thanks to a collaboration with Global Forest Watch – the international forestry watchdog – and Google (which stores the vast amount of radar satellite data analysed by the alerting system), Reiche's team at WUR has now been able to scale up to cover the entire African rainforest.


A view of every patch of cleared forest

As well as allowing us to look through cloud cover, radar imaging also means we can zoom in to the forest, which is exactly what is needed in Africa, says Reiche. That’s because deforestation is happening in relatively small patches, in contrast to South America and Indonesia where large areas are often cleared for soya and palm oil plantations. Broadly speaking, there are two main causes of deforestation in the Congo Basin. Commercial entities cut tropical hardwoods destined for trade, while local residents cut trees, processing the wood into charcoal and using the cleared land for agriculture.

The commercial entities – local traders, but also major players from China, for example – only remove the trees they need for export purposes. “That’s known as selective logging,” says Reiche. “They create paths through the jungle and then to the left and right of those paths they just cut the commercially valuable trees they can sell.” That kind of deforestation is only visible if you zoom in very closely on the map. The same is true for the patches of rainforest cleared by local residents. The RADD technology can zoom in closely to a 10x10 metre patch, meaning you can see gaps in the forest canopy after trees have been logged.

ESA satellite Sentinel-1 uses radar technology to create images of deforestation in the African rainforest. Image: ESA

Deforestation for all to see

The visibility that this system provides may be great, but how does that stop illegal logging? “Our alerting system is being used by the Global Forest Watch,” says Reiche. “They’ve been monitoring global deforestation for years and also have excellent partnerships with the governments of tropical countries, as well as with other organisations fighting against deforestation. These include NGOs such as Greenpeace and WWF, but also local stakeholders such as the rangers who protect national parks. The Global Forest Watch app will soon give those rangers access to the RADD alerts too: they'll be able to see on their mobile phone where areas are in the process of being logged, so they can intervene.”

The environmental conservation organisation WWF is delighted with Wageningen’s RADD alerting system, says its adviser Jorn Dallinga, who happens to be a WUR alumnus. “We now have a much better idea of where trees are being logged and we can act on that. When all we had was the optical satellite imagery it was often too late to intervene. Now we can swing into action more promptly, and it's essential that we do so because deforestation is occurring at a rapid pace in the Congo Basin. The African tropical rainforest is rich in biodiversity, and is home to endangered animal species such as the forest elephant and the mountain gorilla. Its peat soils also provide a natural way of capturing CO₂, and releasing it will lead to even greater acceleration in climate change.”

Observation = prediction

So is the idea now to immediately go and tackle any new RADD deforestation alerts? Yes, ideally, says Dallinga. “But it's often complicated to enforce locally, because of limited capacity, ambiguous mandates and regulations. You’re also dealing with a range of different groups, including local communities who cut trees for their own use, and traders who sell tropical hardwood illegally. Those traders might actually be employing the local community to cut trees for them.”

The difficulty of enforcement is why WWF has moved into making deforestation predictions. The environmental NGO has collaborated with consultancies and technical experts to develop an Early Warning System which is due to be piloted in Gabon in the spring of 2021.

It’s based on the RADD deforestation alerts, combined with around 30 other variables such as the road network (accessibility) and population density. Dallinga: “By predicting where trees are likely to be logged within the next six months, you can better protect vulnerable areas such as national parks or carbon-rich peatlands from illegal deforestation.”


The effect of deforestation in Congo. Timber loggers build roads and cut trees on both sides. Image: Logging Off

Local community clears forest for small-scale agriculture. Image: Pieter Moone, KU Leuven

Patrol teams

When there's an awareness at the national level of which regions need to be prioritised, regional authorities can set up patrol teams with representatives of other stakeholder groups such as local government, NGOs, businesses and local communities. The objective is to get both commercial businesses and local communities on board with reducing illegal logging, says Dallinga. “We’re looking for sustainable solutions. Rather than handing out fines, it’s better to work with the local community. What fuel sources are available to them as an alternative to charcoal? And what other sources of income are available to them besides illegal logging? Many have lived in the rainforests for centuries so it's in their interest to preserve it too.”

WWF also wants to work with the private sector to look at more sustainable forms of logging. This could take the form of sustainable forestry practices, taking account of issues such as biodiversity preservation. There’s a long way to go, but Dallinga is optimistic. “We expect good results from the local partnership approach. And besides, once it’s understood that illegal logging can be monitored almost in real-time (every six to 12 days when the radar satellite is producing images - Ed.) and can even be predicted, this should have a deterrent effect.”

Objective: monitoring deforestation globally

WWF hopes the pilot in Gabon will optimise the predictive model. Dallinga: “We can already predict 50 per cent of tree felling over the next six months. There’s an 80 per cent certainty that deforestation will occur in those locations.” Eventually, WWF hopes to make the model available to other countries in Africa, such as Congo and Cameroon. In fact, Wageningen’s RADD alerting system is already producing images of those regions. And it won’t stop there. Reiche: “In South America, where lots of rainforest is being cleared for soya plantations and livestock, the RADD alerting system would also provide a much better and quicker view of what’s happening on the ground. The same applies to any area of rainforest on Earth.”


For more information about the RADD deforestation alerting system, visit our website.

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