The arid areas on the earth are greener because of the increased CO2 concentration

(Scientists have long suspected that an area becomes greener due to increased atmospheric carbon dioxide, observations have been made since the early 1980s in defense figures. fine. Currently, a study of global dry areas has shown an effect of absorbing carbon dioxide causing a gradual green color from 1982 to 2010.

Focusing on areas of southwestern North America, remote areas of Australia and some parts of Africa, Randall Donohue of CSIRO (Commonwealth Scientific and Industrial Research Organization) in Canberra, Australia and his colleagues developed and applied a mathematical model to predict the scale of the effect of increased carbon dioxide concentrations.

They then tested this prediction with satellite images, and showed the effects of carbon dioxide on the forest separately from other influencing factors such as rainfall, air temperature, total amount of light and changes in land use.

The team's model predicted that the coverage would increase by about 5-10% when atmospheric carbon dioxide concentrations increased by 14% during the study period. Satellite data also showed that the coverage increased by 11% after adjusting the rainfall and productivity data 'strongly support our hypotheses', the team said. .

'Many studies show an average increase in vegetation globally and there is much speculation about the cause of this phenomenon'. Donohue is from the Land and Water Research Department of CSIRO, who is the lead author of the new study. 'Up to this point, researchers have linked greening to climate change quite clearly, such as an increase in temperature in cold places or an increase in rainfall in places. drought. Many studies have speculated about the impact of CO ₂ , but it is still difficult to get excited. '

Donohue and colleagues published their findings in an article in GeophysicalResearch Letters, a journal of the American Geographic Society.

The team looked for signs of CO ₂ absorption in arid areas, Donohue said: 'satellites give very good observations about changes in total area covered by plants, and here. is in warm, dry environments where the effect of CO ₂ is expected to affect most of the coverage '. Coverage is a sign, he explains, because: 'a leaf can absorb more CO2 from the atmosphere during photosynthesis, or lose less water to the air during photosynthesis. , or both, due to high CO ₂ '. That is the CO2 absorption effect.

But coverage in wet and warm places, such as tropical rainforests, has expanded as it can be received and does not seem to increase when CO ₂ levels are higher. In contrast, in warm, dry places, the coverage is lower, so plants in these areas will produce more leaves if they have enough water to do so. "If CO ₂ increases the use of water by individual leaves, plants will react by increasing their total number of leaves, and this needs to be measured from satellites ," explained Donohue.

To understand the actual effects of CO ₂ absorption compared to other environmental factors, researchers first calculated the green mean of each position over a period of 3 years to calculate the change. change in soil moisture and then group the green data from different regions based on the total rainfall. The team has determined the total maximum area of ​​foliage of each group can determine for a certain amount of rainfall, and monitor changes in foliage for 20 years. This has allowed scientists to eliminate the effects of rainfall and other climatic factors and discover long-term greening trends.

In addition to dry greening areas, the efficiency of CO ₂ absorption also changes the vegetation that predominates in these areas. 'Woody plants are overwhelming on the land where grass grows, and this may be related to the effects of CO2 , ' said Donohue. 'Long-lived woody plants have deep roots and seem to benefit more than grass when CO2 concentrations increase'.

'The effect of higher CO ₂ levels on plant function is an important process that needs more attention , ' says Donohue. 'Even if there is nothing else in climate change such as elevated CO ₂ levels, we will still see major environmental changes due to the effects of CO ₂ absorption' . This research is funded by many organizations, including Australia's Land and Water Research Community.