It’s not like we need a new reason to save our trees, but since deforestation is already on its pinnacle this particular reason is such that will leave you in splits on whether to eat or to breathe. A new study has brought a new light to the pattern of why the Monsoon over Indian subcontinent is weakening on a frequent basis. And how this weakening is related to the land use and land cover.
To understand the how these two are related, we have to understand the term Evapotranspiration. Evapotranspiration is the phenomenon where water from land is transferred into the atmosphere, either by evaporation and transpiration. This evapotranspiration has seen a decreasing a trend over the years.
How this works is if the soil is weak at a particular location, mainly due to deforestation, then chances of excess water to stay put is more. Since there is less water to go back in the environment, hence less of it will fall back, resulting in defiance.
The weakening of Monsoon is seen at a tremendous rate over North and Northeast India. This is due to the large scale extensive deforestation, which leads to the recycling of the rainfall over a region. This component can be observed in the north and northeast India during the August & September when nearly 20-25 per cent of the Monsoon rainfall received is recycled.
Subimal Ghosh is an associate professor at the Department of Civil Engineering in IIT Bombay who happens to be one of the authors of the study said, “The recycled component is important in north and northeast India because monsoonal winds in this region are internally circulated due to the presence of the Himalayas.”
Moreover, due to less moisture in peak of summer in the India soil, evapotranspiration is less distinct at that point of time. “It is only in the latter half of the monsoon that the soil picks up moisture from oceanic sources,” Ghosh added.
The team that came up with the study compared the grassland cover of 1980s India to 2000s. It was seen that back in 1980s, the woody grasslands were more as compared to 2000s, especially in Northeast India. There was a large scale deforestation observed over the years in the area as the demand of tea plantation and agriculture increased. Overall almost 20% of the leaf cover was reduced over Northeast India in all these years.
Following to this, the task was to observe the rainfall figures of all these years. The comparison came in negative implying there was a significant decrease in the rainfall over the years over Northeast India.
Previous to this study there were reports that blamed the heating of parts of Indian Ocean which may have some effect implying the weakening of Monsoon over India.
“There is no denying that monsoon is a large-scale phenomenon, where macro-factors such as warming of the Indian Ocean are at play. This is the first time the effect of local factors like deforestation has been considered,” Ghosh said.
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Originally published: Nature.com
