Is China going green faster than expected? A study published at the end of May in the journal Geophysical Research Letters suggests that trees planted by humans show greater growth than natural forests. According to scientists, trees from reforestation respond more strongly to increased atmospheric carbon dioxide.
Since 1978, the Middle Kingdom has planted 66 billion trees. An additional 34 billion will be reforested by 2050 as part of a gigantic project called the “Great Green Wall”. This aims to transform the desert steppes of Inner Mongolia into vast forests. The objective is twofold: to slow the progression of the Gobi and Taklamakan deserts, while strengthening the country’s capacity to capture carbon.
Researchers were interested in the differences between natural and planted forests, to understand how species diversity, plant density and age can influence reactions to increasing CO2 and climate change.
“Planted forests are widely used in climate change mitigation strategies, but most global ecosystem models do not distinguish between forest types and do not adequately represent age-related dynamics”explains Yuhang Luo, researcher in landscape ecology at Peking University.
To obtain their results, the scientists relied on satellite data to track leaf area index and measure forest cover density, reports Live Science. With the aim of quantifying the development of different types of forests.
+66% growth for reforestation
The observation is clear: planted trees grow 66% faster than natural woods. Several explanatory factors are pointed out, such as the choice of seeded species (often eucalyptus or poplar trees which grow quickly) or the active management from which reforested plants benefit. Green space maintenance agents eliminate competing vegetation and fertilize young shoots, which promotes their development.
“Planted forests can be a powerful tool, in the short term, for carbon sequestration, but this benefit remains limited over timetempers Yuhang Luo. For carbon storage and long-term resilience, natural forests remain irreplaceable.”
This observation has already been documented by science. Another study of Chinese forests found that, in their early years, natural forests accumulate more carbon above ground than planted ones. Results which must however be considered with caution.
“Land use management works in more subtle and specific ways than we had assumedYuhang Luo admitted. It’s not just about planting more trees. It’s also about knowing when to plant them, which species to choose and how to manage them over time.” Above all, the authors hope that their work will help guide reforestation efforts, to further limit the effects of climate change. The challenge is no longer to plant more, but to plant better.
