If you believe that the Sahara is covered only with golden dunes and scorched rocks, then you are not alone. Perhaps it is time to put an end to that notion.
In an area of West Africa, 30 times larger than Denmark, an international team led by researchers from the University of Copenhagen and NASA has counted more than 1.8 billion trees and shrubs. The 1.3 million km2 area covers the Sahara Desert, the western part known as the sub-humid regions of Western and Western Africa.
“We were very surprised to see that a lot of trees actually grow in the Sahara Desert, because until now, most people thought that no one had actually seen. We counted millions of trees in the desert alone. This would not be possible without this technique. Indeed, I think it marks the beginning of a new scientific era, “Martin Brandt, assistant professor at the University of Copenhagen’s Department of Geosciences and Natural Resource Management, has now published the lead author of the study’s scientific article. Nature.
This work was achieved through a combination of detailed satellite imagery, and intensive learning provided by NASA – an advanced artificial intelligence method. Normal satellite imagery is unable to identify individual trees, they are literally invisible. In addition, a limited interest in counting trees outside the forested areas led to the prevailing view that there were almost no trees in this particular area. This is the first time that trees have been counted in a large arid region.
Role of Trees in Global Carbon Budget
According to Martin Brandt, new knowledge about trees in such arid regions is important for several reasons. For example, they represent an unknown factor when it comes to the global carbon budget:
“Trees outside forest areas are usually not included in climate models, and we know very little about their carbon stock. They are basically a white space on the map and an unknown component in the global carbon cycle, ”explains Martin Brandt.
In addition, the new study may contribute to better understanding the importance of trees for biodiversity and ecosystems and for people living in these areas. In particular, enhanced knowledge about trees is also important for developing programs promoting agroforestry, which play a major environmental and socio-economic role in arid regions.
Thus, we are also interested in using satellites to determine tree species, as tree types are important with respect to their value to local populations who use wood resources as part of their livelihoods Huh. Trees and their fruits are eaten by both livestock and humans, and when preserved in fields, trees have a positive impact on crop yields, as they improve the balance of water and nutrients, ”Geo – Professor Rasmus Fensholt of the Department of Science and Natural Resources explains. Management.
High capacity technology
The research was conducted in collaboration with the Department of Computer Science of the University of Copenhagen, where researchers developed intensive learning algorithms that made it possible to count trees in such a large area.
Researchers show intensive learning models of what a tree looks like: they do this by feeding thousands of images of different trees. Based on the recognition of tree shapes, the model can then automatically identify trees over large areas and thousands of images. The model only requires hours that would take thousands of humans many years to achieve.
When it comes to documenting changes globally, contributing towards the global climate goals. We are motivated to develop this type of profitable artificial intelligence, ”says Christian Igel, professor and co-author of the Department of Computer Science.
The next step is to expand the count to a much larger area in Africa. And over the long term, it aims to create a global database of all trees growing outside forest areas.
University of Copenhagen
Header Image Credit: Martin Brandt