Understanding regional vegetation dynamics and historical changes in rocky desertification is crucial for assessing the sustainability and potential of afforestation in karst regions.

In a recent study published in Earth's Future on April 5, researchers led by Prof. WANG Kelin from the Institute of Subtropical Agriculture of the Chinese Academy of Sciences have found that maize cultivation and tree felling three hundred years ago triggered severe rocky desertification in the karst area of southwest China.

Scientists have developed a method to identify historical human disturbances using dating methods from karst depression sediments, including ¹³⁷Cs, ²¹⁰Pb_ex and charcoal ¹⁴C. The first-ever pollen record in karst depression sediments, combined with comprehensive dating methods and historical documents was presented.

According to the researchers, the forest evolution in southwest Guangxi is a three-stages of "virgin forest-deforestation-sparse tree planting" over the past three centuries. It was probably a lush mixed deciduous and coniferous forest at the beginning. However, maize cultivation, along with explosive population growth and migration, accelerated mountain reclamation and deforestation, leading to severe rocky desertification around the 1780s. Since the 1930s, sparse afforestation has taken place, increasing economic benefits.

Interestingly, they concluded that the introduction of maize, population growth, and migration accelerated mountain reclamation and deforestation, leading to historical rocky desertification in the region, making it difficult for some karst areas to restore forest landscapes.

"Previous studies on historical rocky desertification and human activities in karst areas were mainly relied on historical literature records," said Prof. YUE Yuemin, corresponding author of the study. "Our findings, for the first time, provide important scientific evidence and basis for establishing ecological restoration baselines and implementing precise afforestation and grassland restoration in karst areas."

This study was supported by the National Key R&D Program and the National Natural Science Foundation of China.

The pollen records in the sediment. Three stages were divided according to the critical pollen percentage variations. The isotopic dating ages are shown on the left. (Image by YUE Yuemin) 

The forest evolution history over the last three centuries. (a) A diagram of tree cover and soil environment at three stages at our sampling site. (b) Forest area variations in Guangxi Province during 1730-1970. (Image by YUE Yuemin)