HANOI, Sept 28 (Vietnam News/ANN): The burning of straw, plant byproducts and other waste on fields near airports produces smoke that affects visibility for pilots and poses a high risk to flight safety, said an official from Northern Airports Authority under the Civil Aviation Authority of Vietnam.

Head of Safety Management of Northern Airports Authority Trưong Hieu Linh told the Vietnam

The team found that the crimson king maple, swamp white oak, hackberry, and copper beech trees offered the highest protection factor (PF) (greater than three, meaning its shade allows you to remain outside three times longer than if you had no protection from the sunshine), while the maidenhair tree (ginkgo) and the red maple returned the lowest PF values

Dr Sivarajah told BBC News: "What's interesting about our work is that we found the main driving factor of variation in UV protection among trees is related to crown geometry."

The trees with crowns that were less transparent and were wider offered greater protection. They also found that it was species with a higher level of shade tolerance that were more effective when it came to UV protection.