Safa Motesharrei, a systems scientist, stands in a forest of trees. He uses satellite images from NASA to assess deforestation.
New findings from university researchers show that deforestation might impact local temperature changes, which in turn could affect agricultural production.
A team from this university’s National Socio-Environmental Synthesis Center published a paper on this topic in Nature Communications on March 31. They were the first researchers to conduct this kind of analysis using high-resolution NASA satellites to gather data on a global scale.
The research determined that albedo, the amount of the sun’s radiation reflected off Earth’s surface, and evapotranspiration, the transportation of water into the atmosphere from the planet’s surface, are the main players in shifting local temperatures.
“Lots of crops are very sensitive to changes in temperature, especially increased temperature,” said systems scientist Safa Motesharrei, co-author of the paper. “These changes are nonlinear, meaning that you increase the temperature a couple of degrees, the yield suddenly drops down. That could cause catastrophe for the agriculture, for the farmers and for the food.”
Motesharrei said forests have a low albedo due to their trees’ dark and rough surfaces, meaning they have a lesser ability to reflect sunlight and instead absorb it. This phenomenon leads to higher temperatures.
Evapotranspiration in forests, on the other hand, causes a cooling effect as precipitation evaporates from the trees.
When forests are cut down in tropical regions, the atmosphere loses the cooling effect from the forests’ evapotranspiration, which could increase the local temperature by a few degrees.
The idea of using satellite information to collect this global data came to professor Yan Li, the lead author of the paper, after looking at previous studies that used satellite data for specific regions or in-situ measurements, which collect measurements from the ground.
“I was curious, what if we expand the study area from a region to all the world, as we know forests at different locations or latitude can have quite opposite influence on climate,” Li wrote in an email.
The problem with in-situ measurements is that they are limited to specific geographical regions, Motesharrei said. And climate models, which were also used in earlier research, produce uncertain results, as different models have different variations.
“It was an innovative use of satellite data,” said Ning Zeng, an atmospheric and oceanic science professor. “The land is very heterogeneous. You have building here; next door, we have Greenbelt Park. Then you have the roads; you have crop land a little further away.”
The satellite data was able to distinguish between these different kinds of surfaces and provide more accurate data, said Zeng, who was not involved in the research.
The research involved observing patterns temperature change patterns during various seasons and times of day. The differences between the northern and southern hemispheres were also noted.
Motesharrei said the team plans to move the research forward in different directions by comparing its results with those of climate models and observing the relationships that might exist between different patterns. Another extension lies with using NASA satellite data to observe the changes in vegetation activity levels in certain areas and how they could be affected by temperature or precipitation changes.
“It gives us a way to quantitatively estimate either the benefit of forest on climate or the cost if we lose them,” Li wrote. ”The fact is that we had lost a lot of forests in the past and we are still losing them at present. If no actions are taken and this trend continues, then we would have to pay much more in the future to compensate the mistakes we made today.”
CORRECTION: Due to a reporting error, a previous version of this story incorrectly stated that Safa Motesharrei is a professor. He is a systems scientist. This article has been updated.
