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Urgent need to understand the relationship between fog and ecosystem health

By Sheree Bega Time of article published Jun 23, 2020

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The fog that envelops the arid Namib Desert is a vital source of moisture for plants that have adapted to survive in the oldest and one of the driest deserts on earth.

This has been known for several decades through the pioneering work of legendary southern African desert researcher Dr Mary Seely and from field observations of other researchers, says hydrologist Dr Lixin Wang.

But as climate change reduces fog levels across the planet, there’s an urgent need to understand the relationship between fog and ecosystem health.

Wang, an associate professor in the school of science at Indiana University-Purdue University Indianapolis (IUPUI), is the senior author of a new study led by the IUPUI that shows for the first time that it is possible to measure vegetation's response to fog using satellite images.

“This study not only makes the fog impact monitoring from a large spatial scale possible, but also provides a powerful tool to make continuous measurements of fog's impact on vegetation,” he says.

This is essential to fully understand the impacts of climate change on vegetation communities in the Namib Desert, a World Heritage Site, cherished for its ecological rarity.

“Fog formation requires cold temperature. As the global temperature is continuously increasing - the Namib Desert is no exception - fog frequency is expected to decrease. As many plant species living in the Namib Desert rely on fog to survive, this will adversely affect vegetation in this region,” he says.

Past work in the Namib Desert focused on individual plants using “discrete sampling due to technical constraints and logistical issues” at remote field locations. “All of these limit our understanding of the large-scale impacts of fog on vegetation in the Namib Desert and make predictions of responses of this unique system to future climate change very difficult.”

The study, Satellite Observed Positive Impacts of Fog on Vegetation, was published in the journal Geophysical Research Letters, by a team from IUPUI, Shihezi University, the Gobabeb-Namib Research Institute in Walvis Bay and the University of Chinese Academy of Sciences.

It is based on optical and microwave satellite data, together with information from weather stations at two locations operated by the Gobabeb Namib Research Institute, with the satellite data obtained from Nasa and the US Geological Survey.

The fog readings were taken between 2015 and 2017. The results indicate that fog is the main water input in “maintaining vegetation ecological functions at the study sites during rainless periods. Satellite-based continuous observations clearly show plant communities over a larger area benefits from fog”.

The reduction of fog threatens other important areas such as the Atacama desert in Chile, a World Heritage Site, and the redwood forests of California.

“We will use the techniques developed in this research to continue to monitor fog's impact on vegetation,” says Wang. “With an accumulation of longer-term data, we will be able to better evaluate the impacts of fog reduction on vegetation growth within the Namib Desert, and to make more accurate predictions of future vegetation dynamics across the desert.”

The loss of fog endangers plant and insect species in these regions, many of which don’t exist anywhere else, says Na Ziao, a visiting student at the IUPUI and the study’s first author.

“The impact of fog loss on vegetation is already very clear. If we can couple this data with large-scale impact assessments based on satellite data it could potentially influence environment protection policies related to these regions.”

The Saturday Star

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