To understand trees and the forest, you have to see, smell and touch them. That takes time. And that is why, in recent years, other observation techniques have been developed. One of them, “airborne spectranomics,” enables detailed surveys of plant biodiversity from the sky.
With laser eyes
Spectranomics uses hyperspectral sensors, mounted on drones or airplanes, to capture high-resolution images of the vegetation at different wavelengths in the spectrum range from visible to infrared (400 -2,500 nm). By analyzing these images, researchers can then identify the different plant species of the forest, which is normally done in the field but is currently impossible by satellite.
A unique signature
Each plant has a unique spectral signature based on the chemical and structural characteristics of its foliage. It is therefore possible to identify the species as well as observe changes in their activity status. This enables researchers to link changes in plant biodiversity (what’s there and what’s not) to their consequences on the functioning of terrestrial ecosystems (how nutrients circulate in the forest).
Spectranomics yields plant biodiversity data approaching the high-resolution of traditional approaches, but on a significantly broader scale. It bridges the gap between ground-based surveys and satellite imagery. Proof of its enormous potential is that researchers using this technique have managed to map canopy tree diversity in remote, difficult-to-access areas such as the Amazon forest.
A Canadian observatory
Closer to home, five Canadian researchers in biodiversity and remote sensing recently created the Canadian Airborne Biodiversity Observatory (CABO). Having received funding in the amount of $4 M from the Natural Sciences and Engineering Research Council of Canada (NSERCC), its objective is to study changes in plant biodiversity across Canada, using spectranomics in combination with ground-based studies and satellite imagery analyses. CABO may very well revolutionize the way plant biodiversity data are acquired across Canada and around the world.
The observatory will use high-fidelity spectroscopy to measure foliar spectra of Canadian plant species. The data for each plant will be associated with a species kept at the Marie-Victorin herbarium at Université de Montréal, one of the largest in Canada. This foliar spectral database will be of tremendous value for taxonomy, ecology and remote sensing research, and will provide the foundation for all future applications of high-resolution plant biodiversity surveys based on hyperspectral imagery.
Etienne Laliberté is professor of ecology at Université de Montréal and researcher at the Biodiversity Centre of the Institut de recherche en biologie végétale (IRBV). The institute, a focus of excellence in research and teaching, is located at the heart of the Jardin botanique de Montréal and is the result of a partnership between Université de Montréal and Ville de Montréal (Espace pour la vie Montréal).
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