Looking at remote sensing data from NASA’s satellites, we’ve discovered that over the last two decades, the Earth has increased its green leaf area by a total of 5 percent, which is roughly five and a half million square kilometers—an increase equivalent to the size of the entire Amazon rain forest.

The two countries that have been most responsible for the global greening came as a surprise to us. We found that China and India—the world’s first and second most populous and still-developing countries—are leading the world in greening due to widespread crop farming.

But is all of this extra leaf cover from agriculture helping or hindering our planet’s health?

Each year, about 10 to 11 billion tons of CO2 is emitted into the atmosphere from carbon sources, such as burning fossil fuels and tropical deforestation. About half of those emissions are stored temporarily in equal parts in the oceans, soils, and land plants—our Earth’s so-called carbon sinks.

Green leaves produce sugars using energy from the sunlight to mix CO2 absorbed from the surrounding air with water and nutrients soaked up from the ground. These sugars, whose production helps eliminate CO2 from the atmosphere, are the source of food, fiber, and fuel for life on Earth. Based on this knowledge, more greenery sounds like a good thing.

Here’s the catch. Not all land plants are created equally.

Part of the green effect in China can be attributed to an ambitious tree-planting initiative known as the Green Great Wall. However, the vast majority of greening in China and India stems from the intensive agricultural use of land that helps feed the 1.4 and 1.3 billion people who live in those countries. China and India each have about two million square kilometers of croplands, which has not changed much since the early 2000s. In contrast, total food production of grains, vegetables, and fruits has increased greatly, about 35-40 percent, in that time.

Read the full article about earth's expanding green area by Chi Chen and Ranga Myneni at Futurity.