Vegetation Change in China
In fact, vegetation reflects both visible light (the kind we see with our eyes) and other radiation from invisible parts of the electromagnetic spectrum in unique ways. Vegetation is green because it absorbs almost all other wavelengths of visible light except green, which it reflects back to our eyes or to a satellite.
It is easy for people to spot vegetation and figure out where it is thick and healthy and where it is sparse or struggling. It is also easy for people to identify the grass in our lawns or the woods at the park. However, it is not easy for a satellite orbiting 700 kilometers above the Earth.
Background
Vegetation Indices
Vegetation Indices are important tools for mapping and monitoring the world’s vegetation. By measuring how much visible and near-infrared light is reflected off the surface, scientists can calculate the “greenness” of the vegetation. The vegetation indices can show the vegetation situation in the target area.
The most commonly used way for identifying vegetation is to compare the amount of reflected visible light to the amount of infrared light. Areas reflecting low levels of visible light and high values of infrared light are likely covered by leafy vegetation. Scientists use formula to get figure out the situation in the target area.