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China and India – two economic powers of Asia – contribute significantly to the greening of the planet, revealed a new global study released Monday.
The world now has about 5.5 million square kilometers of additional green leaf area compared to 2000. Much of this increase is due to greening in China and India. China contributed 25% to this increase, while India added 6.8% of the total net increase in leaf area between 2000 and 2017.
The contribution of the two countries to greening is much greater, although their area of vegetation is lower than that of some developed countries. China has 6.6% and India only 2.7% of the world's planted area. The increase in total leaf area recorded in India is equal to that observed in the United States or Canada, each of which has a plant area three times larger.
Greening refers to the increase in total leaf area – forests, cropland, orchards, monocultures, commercial plantations.
The increase in green areas is mainly due to a 35% increase in food production in multi-crop countries, aided by the use of fertilizer and the availability of surface irrigation and underground. China has also undertaken large-scale rejuvenation of forest areas and reforestation of degraded lands.
In China, greening comes from forests (42%) and cultivated land (32%), but in India it comes mainly from cultivated land (82%) with a minor contribution from forests (4.4%).
Previous studies have shown that carbon dioxide fertilization is the main reason for greening the land. But this study found that greening is more due to changes in land use. The study is based on satellite data from NASA MODIS sensors. These sensors observe the entire earth twice a day at a resolution of 500 meters.
"China and India account for one-third of greening, but only represent 9% of the world's vegetation area. This discovery is surprising given the general notion that there is soil degradation in populated countries due to over-exploitation, "said Chi Chen of the Earth and Environment Department of Boston University, principal investigator, at India Science Wire. The study was published in the journal Sustainability of nature.
However, experts believe that increased greening from cropland and plantations should not be seen as compensation for forest loss in Brazil, Indonesia and other parts of the world. "Greening due to intensive agriculture does not improve the earth sinks because the crops' carbon is rapidly returning to the atmosphere," explained Dr. Victor Brovkin of the University of Ottawa. Max Planck Institute of Meteorology, Germany, also co-author of the study.
"The contribution of forests to the greening of India being minor (4%), it was not explored in detail in this study. However, it is important to find a general trend towards greenery in the natural vegetation (forests) in India, unlike some recent studies reporting a tendency to browning, "commented Dr. Rajiv Kumar Chaturvedi (Pilani BITS) , Goa Campus), and member of the research team, while speaking at India Science Wire.
When asked how the new study compared with forest area statistics from the Forest Survey of India (FSI), Chaturvedi said the two could not be compared because their contexts and objectives were different. "I think the FSI estimates are supposed to be more robust because their estimates are based on thousands of ground observations, in addition to satellite data. However, FSI estimates will gain credibility if their field data and satellite assessment are made publicly available and subject to rigorous peer review, "he added.
The research team included Chi Chen, Taejin Park, Baodong Xu and Ranga B. Myneni (Boston University); Wang Xuhui, Shilong Piao, Zaichun Zhu (Peking University); Rajiv K. Chaturvedi (BITS, Goa Campus); Richard Fuchs (Institute of Meteorology and Climate Research, Germany); Victor Brovkin (Max Planck Institute of Meteorology, Germany); Philippe Ciais (Paris Saclay University, France); Rasmus Fensholt (University of Copenhagen); Hans Tømmervik (Norwegian Institute for Nature Research); Govindasamy Bala (Indian Institute of Science, Bangalore); Ramakrishna R. Nemani (Ames Research Center, NASA).
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