Watts UP With That? (Anthony Watts) / Charles Rotter
Human Activity in China and India Dominates the Greening of Earth,
NASA Study Shows
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,
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
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
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,"
"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
The consequences for sustainability and biodiversity in those
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
Humans are incredibly resilient. That's what we see in the satellite
China and India Lead in Greening Due to Human Activity