We may no longer be able to rely on green cover to cut air toxicity, a new study has asserted. The study has said that air pollution is causing malnutrition in trees by affecting fungi that plays the essential role of providing mineral nutrients to tree roots. The study conducted by a team from the Imperial College in London highlighted the symbiotic relationship between plant and the mycorrhizae fungi and how it is crucial for the transport of nutrients such as nitrogen, phosphorus, and potassium from the soil to the roots.

Published in the journal Nature, the study was conducted by examining 40,000 roots from 13,000 soil samples at 137 forest sites across 20 Europian countries for a period of 20 years. This practice allowed the researchers to study in detail the fungi's tolerance to pollution.

In exchange, the plant-fungal relationship provides the soil carbon from the tree. It was discovered as part of the study that discoloured leaves and excessive falling of leaves are signs of malnutrition. In addition, researchers also pointed out that high level of elements such as nitrogen and phosphorus in the mycorrhizae fungi can turn the fungi's nature forcing it to act as a pollutant rather than a nutrient. This can result in an ecosystem where the health of trees is negatively affected, concluded the study.

"There is an alarming trend of tree malnutrition across Europe, which leaves forests vulnerable to pests, disease, and climate change," said lead researcher Martin Bidartondo from Imperial College London while adding, “Processes happening in soil and roots are often ignored, assumed or modelled because studying them directly is difficult, but it is crucial for assessing tree functioning."