by Hanneke van 't Veen
Remote sensing means gathering information from very far away, for instance by observing satellite images of the Earth. Think of Google Maps for instance. At the moment, a lot of satellites around the Earth are non-stop photographing the Earths surface. This does not only mean that you can observe how your city changes but also that scientists around the world can observe what happens to the Earth’s surface over time. They can basically look back in the past! This is very interesting if you would like to understand how the extraction of resources affects nature over time.
But how do researchers do this? Over the past decades, people have developed a range of methods that can observe what happens to forests, water, the weather and even the biodiversity on Earth. The satellite images are basically produced by light that reflects from the Earth, just like normal photographs you make yourself from your surroundings. The information about the reflected light is stored in the photographs and can be used to distinguish forests from non-forests to calculate the effects of wood extraction (see fig. 1). Another example is the measurement of the ‘productivity’ of nature (how fast it grows) from space. This is done by combining different satellite images with information about the reflection of different types of light, such as infrared or visible light. By combining them, you can see how productive an agricultural field or forest is, even very far in the past. It seems almost magical!
Figure 1. Deforestation observed with satellite imagery.