An international study reveals a more complex reality about how trees respond to rising atmospheric carbon dioxide levels. While it’s true that trees have become more efficient in their water usage, their growth rates aren’t increasing as expected. This inefficiency is linked to stomata, tiny openings on leaves that regulate CO2 intake and water loss.
As CO2 levels rise, trees can utilize less water for the same amount of carbon, improving their water-use efficiency. However, in drier conditions, trees close their stomata to conserve water, which also limits CO2 intake. This has led to a discrepancy between the anticipated increase in carbon storage and actual growth rates observed in forests.
Research conducted at Duke University and other institutions indicates that forest growth hasn’t kept pace with earlier predictions based on CO2 fertilization. The study combined models of water movement in trees with data from CO2 experiments, showing that factors like tree height and hydraulic limitations further hinder growth.
The findings challenge the assumption that increasing forest growth can significantly offset human carbon emissions. While forests are vital for biodiversity and carbon storage, expecting them to thrive solely based on CO2 levels overlooks other stressors. Consequently, climate plans should focus on protecting forest resources and preventing deforestation, rather than relying on CO2 as a growth driver.
The study emphasizes that while improved water management helps trees survive in a warming climate, it doesn’t eliminate the need for emissions reduction and strategic forest management. The findings were published in Nature Climate Change.
