Two NASA satellites have watched Earth grow greener over the last 20 years.
Research by the US space agency NASA shows that the amount of the Earth’s surface covered by green vegetation has expanded over the past two decades, and that China and India are the main contributors to the increase.
The greening phenomenon was first detected using satellite data from the mid-1990s, according to the NASA research, published February 11, 2019, and based on nearly 20 years of information collected by instruments orbiting Earth on two satellites. Global “green leaf area” has increased by five per cent since the early 2000s, an area equivalent to the size of the entire Amazon rainforest, according to the study.
Greening of China and India – NASA
One-third of the total increase was attributed to China and India – two of the world’s most populated countries, which are more commonly known for their serious pollution problems. The research indicates that Chinese conservation of forests and tree-planting efforts accounted for the bulk of its contribution. India’s increased green area was due to intensive farming, the data showed.
India continues to break world records in tree planting, with 800,000 Indians planting 50 million trees in just 24 hours.
The recent finding by NASA and published in the journal Nature Sustainability, compared satellite data from the mid-1990s to today using high-resolution imagery.
The greening phenomenon was first noticed by a group of researchers from Boston University, but they were uncertain about whether if its due to human activity or the warming planet and the wetter climate initiated more plants to grow in the northern forests. After further investigation with NASA’s two orbiting MODIS satellites, it became clear, that the two million square miles of extra green leaf area per year are indeed primarily caused by human action.
The map above shows the relative greening (increase in vegetation) and browning (decrease in vegetation) around the globe. As you can see both China and India have significant greening.
The United States sits at number 7 in the total change in vegetation percent by decade. Of course, the chart below can hide where each country started. For example, a country that largely kept their forests and vegetation intact would have little room to increase percent vegetation whereas a country that heavily relied on deforestation would have more room to grow.
“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.”
Comparing the greening of various countries around the globe – NASA.GOV
NASA used Moderate Resolution Imaging Spectroradiometer (MODIS) to get a detailed picture of Earth’s global vegetation through time. The technique provided up to 500-meter resolution for the past two decades.
Both China and India went through phases of large scale deforestation in the 1970s and 80s, clearing old growth forests for urban development, farming and agriculture. However, it is clear that when presented with a problem, humans are incredibly adept at finding a solution. When the focus shifted in the 90s to reducing air and soil pollution and combating climate change the two countries made tremendous shifts in their overall land use.
It is encouraging to see swift and rapid change in governance and land use when presented with a dilemma. It is something that will continue to be a necessary skill in the decades to come.
Despite the encouraging message, the NASA scientists warned that green expansion in the past 20 years was not enough to offset wider human damage to Earth’s ecosystems.
