How a forest as large as the Iberian Peninsula was discovered in the Sahara Desert

In a large area of West Africa somewhat larger than the entire Iberian Peninsula, an international team led by researchers from the University of Copenhagen and NASA has accounted for more than 1.8 billion trees and shrubs. The area, 1.3 million km2, covers the westernmost part of the Sahara desert, the Sahel and what is known as sub-humid areas of West Africa.

"we were very surprised to see that so many trees actually grow in the Sahara desert, because, so far, most people thought there was practically none. We counted hundreds of millions of trees in the desert alone. The discovery would not have been possible without this technology. In fact, I think it marks the beginning of a new scientific age," says Assistant Professor Martin Brandt of the University of Copenhagen, lead author of the scientific article of the study, published in nature.

Area where the forest area is located

The discovery was achieved through a combination of high-resolution satellite images provided by NASA and an advanced method of artificial intelligence. The usual satellite images cannot identify individual trees, as they remain literally invisible.

Moreover, the lack of interest in counting trees outside forest areas led to the widespread view that there were almost no trees in this particular region. This is the first time trees growing in a large drylands region have been counted.

Why is the finding important?

This discovery is important for several reasons, according to Martin Brandt. For example, it provides a hitherto unknown factor in calculating the global carbon budget:

"trees outside forest areas are usually not included in climate models and we know very little about their carbon stocks. Basically, they are a white spot on maps and an unknown component in the global carbon cycle," he explains.

In addition, the new study can contribute to a better understanding of the importance of trees for biodiversity and ecosystems and for people living in these areas. In particular, greater knowledge of trees is also important for developing programmes that promote agroforestry, which plays an important environmental and socio-economic role in arid regions.

The Sahara contains more trees than thought access

"Por lo tanto, también estamos interesados en utilizar satélites para determinar las especies de árboles, ya que los diferentes tipos de árboles son importantes para las poblaciones locales que utilizan los recursos madereros como parte de sus medios de vida. Los árboles y sus frutos son consumidos tanto por el ganado como por los seres humanos, y cuando se conservan en los campos, los árboles tienen un efecto positivo en el rendimiento de los cultivos porque mejoran el equilibrio de agua y nutrientes”, explica el profesor Rasmus Fensholt del Departamento de Geociencias y Gestión de Recursos Naturales.

With high potential

The research was conducted in collaboration with the Computer Science Department of the University of Copenhagen, where researchers developed the deep learning algorithm that made it possible to count trees in such a large area.

Researchers explained how the artificial intelligence system has been able to detect a forest that had so far gone unnoticed. Essentially, scientists fed the system thousands of images of various trees. Based on the recognition of tree species forms, the model can automatically identify and map trees in large areas. The model employs only hours to do what thousands of humans would take several years.

Trees in the area studied geographical.co.uk

"this technology has enormous potential when it comes to documenting changes on a global scale and ultimately contributing to global climate objectives. It's a motivation for us to develop this kind of beneficial artificial intelligence," says Professor and co-author Christian Igel of the Computer Science Department.