Written by Laure Poncet

Climate researchers have found that, despite the projected increase in aridity in dryland areas due to climate change, only a small portion of them will be reduced to desert.

Drylands, which cover 41% of the Earth surface, support more than a third of the world’s population, providing food security and important ecosystem services. 

Over the last decades, many dryland ecosystems have already degraded due to human activity and climate change. 

Xinyue Zhang, a PhD student at the ARC Centre of Excellence for Climate Extremes and lead author of the study, said: “Degraded drylands can lead to biodiversity loss and threaten food security. This can have a considerable influence on human life.” 

“The good news is that, although drylands will expand with climate change, we show that most of them will not desertify.”

Using climate model simulations, the team of researchers assessed the extent of  desertification by analyzing changes in dryland vegetation up to 2050.

Their findings indicate that while about 4% of dryland regions, such as north-east Brazil, Namibia, and Central Asia, experience significant degradation, the majority of drylands are getting greener and more productive with climate change. 

This greening trend is particularly noticeable in southern Australia, western India, southeastern Africa, and northern East Asia. 

Figure 1: Changes in Normalized Difference Vegetation Index – a measure to assess changes in dryland vegetation – under the future climate scenario SSP5-8.5 between period 2031–2050 and 1982–2001. Pixels where at least 50% of models indicate significant changes (p < 0.05), and 75% of models agree on the direction of change are plotted as green to brown. Pixels where 50% of models show significant changes, but less than 75% of models agree on the direction of change are plotted as white. Nonsignificant positive changes are plotted as cyan, nonsignificant negative changes are plotted as violet. 

“One may expect that drylands would gradually become less fertile if aridity increases with climate change, but we show that it won’t actually lead to a general loss of vegetation productivity,” Zhang said.

To explain this greening phenomenon, the team of researchers examined global trends in precipitation and temperature in drylands, as well as CO2 levels. 

“The greening trend we observed aligned with the rise in CO2 concentrations with climate change, suggesting CO2 levels play a role in boosting dryland vegetation growth.”

“This is what we call the CO2 fertilization effect. High CO2 concentrations enhance photosynthesis in plants and reduce their water demand to some degree, enabling them to thrive in dry conditions.”

While most dryland ecosystems will not desertify under climate change, Zhang said poor land use practices could still impact them, highlighting the need to preserve these valuable ecosystems. 

Between 1982 and 2015, 6% of drylands have undergone desertification, and negative land use effects played a key role in most areas.

“Dryland ecosystems are extremely vulnerable to damaging human activities. Deforestation, overgrazing, and mining, are all processes that can lead to their desertification,” she said. 

 “Without appropriate mitigation strategies, this could pose serious challenges to the livelihoods of millions of people, especially in developing countries.”

The study is published in Communications Earth & Environment and was co-authored by Xinyue Zhang and Prof Jason Evans from the ARC Centre of Excellence for Climate Extremes as well as Dr Arden Burell from the Woodwell Climate Research Centre.