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How satellite alerts are tackling deforestation across African countries

Subscriptions to satellite alerts can help tackle deforestation, one of the main drivers of greenhouse gas emissions and biodiversity loss, a new study showed. A group of African countries where organizations received warnings from a service using satellites saw an 18% plunge in forest loss over a two-year period.

Credit image: Flickr / CIFOR

Land-use changes like deforestation account for 6% to 17% of global carbon emissions. And avoiding deforestation is much more effective at reducing emissions than regrowing forests. Needless to say, forests also provide essential support not just for countless ecosystems, but also for human populations.

A group of US researchers wanted to understand whether automated deforestation alerts could help to reduce forest loss. They focused on the Global Land Analysis and Discovery (GLAD) system, which provides frequent, high-resolution alerts when it detects a drop in forest cover. Governments and organizations can freely access the service and receive weekly emails with geographic coordinates of the alerts within the monitored areas.

“The first question was to look at whether there was any impact from having access to this free alert system. Then we were looking at the effect of users subscribing to this data to receive alerts for a specific area,” Fanny Moffette, lead author of the paper and researcher at the University of Wisconsin–Madiso, said in a statement.

Moffette and her team looked at the impact of GLAD in 22 tropical countries across South America, Africa, and Asia from 2011 to 2018. Subscriptions to alerts decreased the probability of deforestation in Africa by 18% relative to the average 2011–2016 levels, the study showed, with no effect seen in other continents.

Africa’s tropical forests include the Guinean Forests and the Congo Basin, an expansive rainforest often referred to as the “world’s second set of lungs”. The continent’s forests store 171 gigatons of carbon, are home to many plants and animals that exist nowhere else in the world, and support an estimated 100 million people.

Calculated using the social cost of carbon for avoided deforestation in Africa, the researchers estimated the alert system’s value to be between $149 million and $696 million. In other words, that’s how much money was saved by preventing deforestation. Protected areas and concessions were the most benefited areas, suggesting alerts can increase the capacity to enforce deforestation policies.

However, being covered by GLAD doesn’t automatically mean less deforestation, the researchers said. Only those African countries in which organizations had actually subscribed to receive alerts saw a decrease in deforestation. Having access to information is good but it’s more important to have people committed to using it.

But the situation is more complex when looking at the entire planet.

While the results were positive in Africa, the researchers found no decline in deforestation in South American or Asian countries, even where organizations subscribed to receive warnings. There are multiple possible reasons for this discrepancy, such as political unrest that limited the use of GLAD in other countries, or a lack of interest in tackling deforestation.

“We see an effect mainly in Africa due to two main reasons,” said Moffette. “GLAD added more to efforts in Africa than on other continents, in the sense that there was already some evidence of countries using monitoring systems in countries like Indonesia and Peru. And Colombia and Venezuela, which are a large part of our sample, had significant political unrest during this period.”

Looking forward, the researchers believe the influence of the GLAD program might grow, as a larger number of governments and organizations register to receive deforestation warnings. Moffette and her team wish to keep looking at GLAD and the effects of the new features recently added to the platform.

The study was published in the journal Nature Communications.

Satellite reveals 8000 years of human settlements

Ancient human settlements have changed the landscape around where they live in such a way that today, 8000 years later, archaeologists can tell if an area was inhabited – using little more than images taken from a satellite.

Deep in the Middle East, beyond the impressive mounds of Earth which marked the bigger, known cities of the ancient Arabic times, lurk overlooked networks of small settlements that probably hold vital clue to understanding ancient civilizations. By combining spy-satellite photos obtained in the 1960s with modern multispectral images and digital maps of Earth’s surface, researchers have managed to create a new method of mapping large scale human settlements. The method was used to map approximately 14.000 settlement sites, spanning over a period of 8.000 years, in 23,000 square kilometres of northeastern Syria – and the results were published in the Proceedings of the National Academy of Sciences.

“Traditional archaeology goes straight to the biggest features — the palaces or cities — but we tend to ignore the settlements at the other end of the social spectrum,” says Jason Ur, an archaeologist at Harvard University in Cambridge, Massachusetts, who is co-author of the study. “The people who migrated to cities came from somewhere; we have to put these people back on the map.”

Such comprehensive maps of previously overlooked features promise to uncover long trends in migration and urban activity, which will give valuable information in truly understanding ancient Arabian civilizations – and not only.

“This kind of innovative large-scale application is what remote sensing has been promising archaeology for some years now; it will certainly help us to focus our attention on the big picture,” says Graham Philip, an archaeologist at Durham University, UK.

This method relies on the fact that human activity leaves a certain mark on the soil, creating the so-called anthrosols, which form from a higher levels of organic matter and have a finer texture and lighter appearance than undisturbed soil, which results in certain reflective properties noticeable by satellites. However, to capitalize on these properties, archaeologists had to be helped by Bjoern Menze, a research affiliate in computer science at the Massachusetts Institute of Technology in Cambridge, who used skills from his day job – identifying tumours in clinical images. He ‘trained’ the software to detect the specific wavelengths of known anthrosols, and this approach proved to be the key of the problem.

“You could do this with the naked eye using Google Earth to look for sites, but this method takes the subjectivity out of it by defining spectral characteristics that bounce off of archaeological sites,” says Ur.

The technique is already redefining a part of what we believed about ancient settlements, renewing speculation about the importance of water to city development. The study found that a large number of sites (even big ones) were located quite far away from rivers or areas of high precipitation.

“The settlement known as Tell Brak, for example, is far too large for what one would expect at such a marginal position,” says Ur. “This is where things get interesting.”

Jennifer Pournelle, a landscape archaeologist from the University of South Carolina in Columbia, agrees:

“These findings validate hypotheses I’ve introduced in southern Iraq — namely that irrigation is an after-effect of urbanization,” she says. “It’s not what enables a city to develop; it’s what keeps them going after soil moisture dries up.”

Pournelle says she hopes to apply the method on an even larger scale, in an attempt to decipher how these inhabited areas worked, especially when they are remote, far away from water, or difficult to access because of local conflicts.

Via Nature