Human Activity in China and India Dominates the Greening of…

Human Activity in China and India Dominates the Greening of Earth, NASA Study Shows and presented with map.

Over the last two decades, the Earth has seen an increase in foliage
around the planet, measured in average leaf area per year on plants and
trees. Data from NASA satellites shows that China and India are leading
the increase in greening on land. The effect stems mainly from ambitious
tree planting programs in China and intensive agriculture in both
countries.

The world is literally a greener place than it was 20 years ago, and
data from NASA satellites has revealed a counterintuitive source for
much of this new foliage: China and India. A new study shows that the
two emerging countries with the world’s biggest populations are leading
the increase in greening on land. The effect stems mainly from ambitious
tree planting programs in China and intensive agriculture in both
countries.

The greening phenomenon was first detected using satellite data in the
mid-1990s by Ranga Myneni of Boston University and colleagues, but they
did not know whether human activity was one of its chief, direct causes.
This new insight was made possible by a nearly 20-year-long data record
from a NASA instrument orbiting the Earth on two satellites. It’s
called the Moderate Resolution Imaging Spectroradiometer, or MODIS, and
its high-resolution data provides very accurate information, helping
researchers work out details of what’s happening with Earth’s
vegetation, down to the level of 500 meters, or about 1,600 feet, on the
ground.

Taken all together, the greening of the planet over the last two
decades represents an increase in leaf area on plants and trees
equivalent to the area covered by all the Amazon rainforests. There are
now more than two million square miles of extra green leaf area per
year, compared to the early 2000s – a 5% increase.

“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,” said Chi Chen of the Department of
Earth and Environment at Boston University, in Massachusetts, and lead
author of the study.

An advantage of the MODIS satellite sensor is the intensive coverage
it provides, both in space and time: MODIS has captured as many as four
shots of every place on Earth, every day for the last 20 years.

“This long-term data lets us dig deeper,” said Rama Nemani, a
research scientist at NASA’s Ames Research Center, in California’s
Silicon Valley, and a co-author of the new work. “When the 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 MODIS data that lets us understand the
phenomenon at really small scales, we see that humans are also
contributing.”

China’s outsized contribution to the global greening trend comes in
large part (42%) from programs to conserve and expand forests. These
were developed in an effort to reduce the effects of soil erosion, air
pollution and climate change. Another 32% there – and 82% of the
greening seen in India – comes from intensive cultivation of food crops.

Land area used to grow crops is comparable in China and India – more
than 770,000 square miles – and has not changed much since the early
2000s. Yet these regions have greatly increased both their annual total
green leaf area and their food production. This was achieved through
multiple cropping practices, where a field is replanted to produce
another harvest several times a year. Production of grains, vegetables,
fruits and more have increased by about 35-40% since 2000 to feed their
large populations.

How the greening trend may change in the future depends on numerous
factors, both on a global scale and the local human level. For example,
increased food production in India is facilitated by groundwater
irrigation. If the groundwater is depleted, this trend may change.

“But, now that we know direct human influence is a key driver of the
greening Earth, we need to factor this into our climate models,” Nemani
said. “This will help scientists make better predictions about the
behavior of different Earth systems, which will help countries make
better decisions about how and when to take action.”

The researchers point out that the gain 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, such as Brazil and
Indonesia. The consequences for sustainability and biodiversity in those
ecosystems remain.

Overall, Nemani sees a positive message in the new findings. “Once
people realize there’s a problem, they tend to fix it,” he said. “In the
70s and 80s in India and China, the situation around vegetation loss
wasn’t good; in the 90s, people realized it; and today things have
improved. Humans are incredibly resilient. That’s what we see in the
satellite data.”

This research was published online, Feb. 11, 2019, in the journal Nature Sustainability.