MOSCOW, October 14. /TASS/. The aerosol haze in the Arctic decelerates the taiga trees’ photosynthesis and depresses growth of plants. The reasons are: industrial emissions, forming the haze, and natural factors, a participant in studies to see how industrial emissions influence sub-Arctic forest ecosystems Vladimir Shishov of the Siberian Federal University told TASS.
Results of the studies, which featured experts from several countries, were published in the Ecology Letters magazine. The work was supported by a grant from the Russian Scientific Foundation.
Arctic haze
The Arctic shading (or haze) is an optic effect in northern latitudes which develops from various aerosol pollutants - elements in industrial emissions. Scientists say this effect began to develop in the mid-20th century, with development of industries in the post-war world. In addition to air contamination, the aerosol affects another important process in sub-Arctic ecosystems - the photosynthesis of trees.
"The shading has decreased the solar radiation on the Earth surface. We have tried to analyze how this decrease of solar energy affects growth of trees. We used the Vaganov-Shashkin model, a most quoted model of the kind in the international scientific community," the scientist said. "We have modified the model and demonstrated that the shading improves the modelling of tree growth on a huge territory, making estimations very accurate."
Reasons and consequences
The scientists analyzed forests on a vast territory - from the Ob’s mouth (West Siberia) to the Khatanga River (the Taimyr Peninsula). They made mathematical modelling, which showed a high correlation between the tree growth and the shading. For the purpose to find out origins of the Arctic haze, the scientists contacted foreign specialists in the atmosphere physics. They offered a few reasons. "First of all, natural phenomena, where the shading develops from major volcanic eruptions or wildfires," Shishov said. "Secondly, active industrial developments, or the man-made factor, are a big contributor."
According to Alexander Kirdyanov of the Russian Academy of Sciences’ Siberian Branch’s Sukhachev Institute of Forestry, the shading above the boreal forests is not permanent. "If we look at maps, showing sulphur dioxide emissions, we can see that in the Arctic there are only a few plants, polluting the atmosphere, and the majority of such plants are in South-East Asia, and also some are in North America and Europe," he said. Those plants due to the specific air circulation in the Northern hemisphere contribute to the Arctic aerosol haze.
"Air streams in the atmosphere’s higher layers may move at the speed of 300 kilometers per hour. Thus, since the streams move from the equator towards the North Pole, countries of South-East Asia also contribute to the haze. Those aerosols may reach big heights and may move from the equator to the North Pole within short time," Vladimir Shishov said.
The decelerated growth of Arctic forests, scientists say, contradicts the warming, registered across the planet. The thing is that northern trees are very sensitive to air temperatures, and in normal conditions higher temperatures would accelerate their growth, that is causing higher productivity of sub-Arctic forests. But the Arctic haze affects interferers with this process. This new factor should be addressed in forecasting tree growth under conditions of the global warming.
"Most high-resolution reconstructions of changing temperatures over recent 2,000 years are based on indirect sources of information, first of all on annual growth rings of trees, which are most sensitive to temperatures, and specifically in northern regions. Such reconstructions are used to forecast temperature dynamics," Kirdyanov said. "From the apparent discrepancies between the positive trend of temperature and the growth of trees emerges a question: how correct are the reconstructions and temperature forecasts, based on the trees’ annual growth rings. Our research offers a solution. "
Emission control
The influence of aerosols on trees is often disastrous. Since 1970, boreal forests at the area of 24,000 square kilometers have died. According to scientists, by the early 2000s the tree growth speed in such forests shrank twice against the 1960s. Only common efforts of countries with reported emissions may solve the problem of aerosol contamination. "Only the entire international community may protect the Arctic from the phenomenon, which we describe in our article," Shishov said. "It could offer a solution to cut the negative influence on Arctic and sub-Arctic ecosystems."
About University
The Northern Federal University is Russia’s first federal university, which in 2006 was organized as a merger of four universities in Krasnoyarsk. It is the biggest university in Russia’s eastern part. In 2019, at the initiative of Governor Alexander Uss, the university organized a department for Arctic studies.