The increased concentration of CO2 in the atmosphere since pre-industrial times isn’t just driving climate change — it’s also making much of the world’s drylands greener with increased plant growth. This is known as the CO2 fertilization effect, and politicians sometimes cite it to rhetorically downplay the negative global impacts of climate change, saying it’s proof that more CO2 in the atmosphere is a good thing.
Our guest on this episode of the Mongabay Newscast says it’s not, and issues a warning against this misleading interpretation. Arden Burrell is a remote-sensing scientist who co-authored the first observation-based study of the desertification of drylands that considers the CO2 fertilization effect, climate change, and climate variability. His new research indicates that while 5 million hectares (12 million acres) of drylands — an area half the size of South Korea — have become desertified, the future of vegetation productivity is an open and debated question. In this conversation with co-host Rachel Donald, he unpacks what the data tell us about the status of the world’s drylands.
Drylands are “the world’s breadbasket,” Burrell says, making up 45% of the world’s agricultural land. Crops grown via these highly complex food systems are already experiencing reduced nutritional value due to rising CO2 levels. Drylands’ climate change-driven degradation has already impacted an estimated 213 million people.
Burrell says this “global greening” can be a net good, but the increase in vegetation could mask other problems. While the CO2 fertilization effect allows plants to use water more efficiently, this also leads to greater amounts of vegetation, and ecologists worry that with more plants in drylands, they may actually take up more water.
“With sustainable agriculture, CO2 fertilization is kind of a net good, but in some parts of the world it has been masking continued overuse, and it is an open question how long that can continue before the degradation gets severe enough,” Burrell says.
Global greening or not, Burrell stresses that his models are only a snapshot of climate impacts on drylands, which require further study. “The fact that plants can slightly grow better in a hotter climate is by no means a justification to run a global climate experiment, which we are currently running … without actually understanding what it’s going to do.”
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Banner image: The spiny forest is a dryland forest at the southern tip of Madagascar, and is considered one of the most ecologically important regions in the world. Many plants here are endemic and possess deep root systems to survive drought. Image by Rod Waddington via Wikimedia Commons (CC BY-SA 2.0).