New Delhi: China and India, the world’s most populous countries, are now greener than they were two decades ago, and they are leading an increasingly greening planet, a NASA report has said.
Data collected in 2019 by NASA satellites reveal that the two developing countries are leading the increase in greening on land, mainly due to their ambitious tree-plantation programs in China and intensive agriculture in both India and China.
In the mid-1990s, the greening phenomenon was first discovered using satellite date by Ranga Myneni of Boston University and his colleagues, but they were unaware if human activity was its cause.
This new update came after analysis of a 20-year-long data record by a NASA tool orbiting the Earth on two satellites. They were equipped with gadgets having high-resolution facility, helping researchers work-out details of what was happening with the planet’s vegetation on ground.
This greening of the planet over the last two decades represents a growth in leafy area on plants and trees equivalent to the area covered by all the Amazon rainforests. According to NASA, there are now more than two million square miles of extra green leaf area per year, compared to the early 2000s, which is a 5% increase.
According to Chi Chen of the Department of Earth and Environment at Boston University, China and India account for one-third of the greening, but contain only 9% of the planet’s land area covered in vegetation – a surprising finding, considering the general notion of land degradation in populous countries from overexploitation.
Rama Nemani, a research scientist at NASA’s Ames Research Center, in California’s Silicon Valley, also a co-author of the new work, said “This long-term data lets us dig deeper. When greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilization from the added carbon dioxide in the atmosphere, leading to more leaf growth in northern forests, for instance. Now, with the new data, that lets us understand the phenomenon at really small scales, we see that humans are also contributing.
China’s contribution to the global greening comes in large part of about 42% from programs including conservation and expansion of forests which were developed in an effort to reduce the effects of soil erosion, air pollution and climate change, which is another 32%. Apart from that, 82% is seen in India which comes from intensive cultivation of food crops.
In India and in China, land used for crop growing is comparable, more than 770,000 square miles, which has not changed much since the early 2000s. Yet, these regions have surprisingly increased both their annual total green leaf area and food production. This target was achieved by multiple cropping practices, wherein a field is replanted to produce another harvest several times a year. Altogether, to feed the large population of these countries, production of grains, vegetables, fruits and more have increased by about 35-40% since 2000.
But this change is not permanent. It may change in future due to numerous factors including both on global scale and the local human level. Increased food production in India is facilitated by groundwater irrigation, if the groundwater is depleted. This trend may progress in a negative way.
Nemani observed that that now we know direct human influence is a key driver of the greening Earth. We need to factor this into our climate models. It would help scientists make better predictions about the behaviour of different Earth systems, which will help countries make better decisions about how and when to take action.
The researchers pointed out that the gains in greenness seen around the world and dominated by India and China does not offset the damage from loss of natural vegetation in tropical regions, including Brazil and Indonesia, the consequences for sustainability and bio-diversity in those eco-systems remains as it is.
Nemani pointed out a positive message in the new finding, saying that once people realized there is a problem, they tend fix it. In the 1970s and 1980s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. “Humans are incredibly resilient. That’s what we see in the satellite data”.
Of the North’s total vegetated land area, 34 to 41 percent showed increases in plant growth (green and blue), 3 to 5 percent showed decreases in plant growth (orange and red), and 51 to 62 percent showed no changes (yellow).
These changes have taken place due to enhanced warming and longer growing seasons in the North, which led to large patches of vigorously productive vegetation that now span one-thirds of the northern landscape, more than 3.5 million square miles. These landscape resembles what was found 250 to 430 miles (400 to 700 km) to the south in 1982.
Compton Tucker, a scientist at NASA’s Goddard Space Flight Center, said “It’s like Winnipeg [in Canada] moving to Minneapolis-Saint Paul (in the US)”.