In fact, some 1.8 billion trees dot part of the West African Sahara and the Sahel Desert and so-called sub-humid regions, a previously uncountable reward that overturns previous assumptions about such habitats, researchers say.
“We were very surprised that a lot (so) trees are growing in the Sahara Desert,” lead author Martin Brandt told AFP.
“Certainly there are vast areas without any trees, but there are still areas with a high tree density, and even among the sandy dunes there are some trees growing here and there,” one of Geography at the University of Copenhagen Assistant Professor Brandt said. .
The survey provides researchers and conservationists with data that can help direct efforts to fight deforestation and more accurately measure carbon storage on land.
“Conservation, restoration, climate change and so on, such data are very important for establishing a baseline,” said Jessie Meyer, a programmer at NASA’s Goddard Space Flight Center.
“In one or two or ten years, the study may be repeated … to see if efforts to revive and reduce deforestation are effective,” he said in a NASA press release.
Finding and counting trees was no easy task. In areas with many trees, thick clumps of growth are clearly visible in satellite images, even at relatively low resolution, and easily differ in bare land.
But where they are more dispersed, satellite imagery can be of very low resolution to exclude individual trees or even small clusters.
High resolution imagery is now available, but problems still persist: counting individual trees, especially in vast areas of the region, is an almost impossible task.
Brandt and his team came up with a solution, tying satellite images to very high resolutions with intensive learning – essentially training a computer program to work for them.
But this did not mean that they could just sit back and wait for the results.
Before the intensive learning program can work, it must be trained, a brilliant process that saw Brandt in person and self-labeled about 90,000 people. It took him a year.
“The level of detail is very high and the model needs to know how all kinds of different trees look in different scenarios,” he said.
“I did not accept abortion and added further training when I saw the trees being classified incorrectly.”
Establishing a Conservation Baseline
It was worth the effort, he said, allowing how many hours millions of people would have counted in a few years.
“Other studies are based on inference and extrapolation, here we look at each tree directly and count it. This is the first assessment from wall to wall.”
The survey was published in the magazine on Wednesday Nature, Covering an area of 1.3 million square kilometers (approximately 500,000 square miles) and analyzing more than 11,000 images.
The technique suggests that “it will soon be possible, with some limitations, to map the location and size of every tree worldwide”, Niall P. of the Department of Plant and Environmental Sciences of New Mexico State University. Hanan and Julius Anchang have written in a review. Research.
Accurate information about vegetation in the desert and other arid regions is “fundamental to our understanding of the global ecology, biography and biochemical cycles of carbon, water and other nutrients,” he wrote by the Review Commission Nature.
Brandt said better information can help determine how much carbon is being stored in these sites, which are not typically included in climate models.
But it is too early to say if having an accurate count of the life of this tree will affect how we understand climate change and its acceleration.
He expects the technology to be used elsewhere to map trees already hidden in 65 million square kilometers (25 million square miles) of areas in the world.
© Agence France-Presse