Diversity - visible from afar

28/Sep/2016

(From "Horizons" no. 110 September 2016)​​​

What looks at first like an abstract pointillist painting in fact shows the forest in Lägern near Baden, comprising 44,000 treetops. This picture illustrates the relatively high degree of diversity of biological activity in this area in July 2015. The rose-red dots, for example, signify trees with a high chlorophyll content. A team from the University of Zurich, led by the geographer Michael Schaepman, is using two highly sensitive measuring devices in an aircraft to measure the diversity of the vegetation.

A laser scanner (lidar) scans the surface and determines the height, density and form of all the trees in this area of 1.5 × 3 kilometres. An imaging spectrometer – rather like a camera – measures visible and invisible colours on 500 different channels at the same time. In this manner, for every two-metre-long image element, the researchers are able to investigate the trees' content of chlorophyll and 15 further substances such as cellulose, water and nitrogen.

In total, six people have been working on this for three years, bringing datasets together and comparing them with information gathered on the ground. Lägern is one of the test areas where highly precise methods for remote sensing are being developed. They will then be applied over larger areas in order to monitor changes in biodiversity systematically. "It means we are in a position to measure the diversity of biological functions to a very precise degree", says Schaepman. They are planning to expand their project to cover grasslands, the rain forests and arctic tundra. "Our distant goal is to equip satellites with measuring devices". ff

Image: UZH: Fabian Schneider, Reik Leiterer, Felix Morsdorf, Michael Schaepman