How Does China Count its Trees? Lasers, Drones, and AI

Counting all the trees in China might seem impossible. The Asian country is nearly 4 million square miles. But counting the trees is vital for the country’s efforts to protect its ecosystems, scientist Qinghua Guo says.

“An accurate estimate of China's tree population is crucial to evaluating forest ecosystem conditions," Guo told LiveScience. Counting the trees can also help them estimate "the amount of carbon that is being locked away in trees,” he added. 

Guo’s team recently published China’s ninth National Forests Resources Inventory. It shows that even though China has huge cities and lots of people, it also has a large number of trees. China has 142.6 billion trees, the Inventory shows. That makes up about 18.8 billion tons of vegetation. 

To count the trees, Guo's team used drones equipped with lidar. It's a light detection and ranging technology. As the drones fly over forests, they ping the tops of trees with laser beams. Lidar measures how quickly the beams of light return. Each tree canopy in the area gets counted. Then, artificial intelligence (AI) models the data for the wider region. Lidar is precise. But Guo notes it still likely missed quite a few trees in its counting.

Guo told LiveScience that the tallest trees in a dense forest can block out the shorter trees. That means the count could be lower than the full number of trees. 

Based on the numbers, China has at least a hundred trees for every person. But it aims to add billions more to its forests in the future. The “Great Green Wall” project is designed to create a tree wall along the border of the Gobi Desert by 2050. It's set to top out at 100 billion trees. The Great Green Wall is already the world’s largest human-planted forest at 66 million trees.   

Reflect: Why might it be important to keep track of the number of trees in a country?

Photo of trees in Shangrao, China from Unsplash courtesy of Stefan Wagener.