Plant species diversity in four different ecosystems represented as spectral variation. Credit: Anna Schweiger, Etienne Laliberté
For global biodiversity assessments, it is important to keep track of how plant species change over time. Researchers from the universities of Zurich and Montréal have now shown that imaging spectroscopy, which will soon be possible via satellite, is a reliable way to keep an eye on plant communities. This makes it possible to monitor the world’s biodiversity in almost real time.
To protect threatened ecosystems, rebuild destroyed habitats, and stop the bad effects of global biodiversity loss, we need data on biodiversity that can be compared across countries. But monitoring biodiversity right now takes a lot of work and costs a lot of money. Also, it’s hard to get to a lot of places around the world.
Satellites can be used to track biodiversity from space.
Anna Schweiger from the Remote Sensing Laboratories at the Department of Geography at the University of Zurich (UZH) and Etienne Laliberté from the University of Montréal have shown that image spectrometry can be used to measure plant diversity in ecosystems ranging from the Arctic tundra to tropical forests. “We hope that our study will help make it possible to see changes in the types of species in Earth’s ecosystems from space in the future. The goal is to give policymakers evidence-based advice on how to protect species and lessen the bad effects of biodiversity loss “says first author Anna Schweiger.
Imaging spectrometers measure how light reflects from the visible range of the electromagnetic spectrum to the shortwave infrared range. The chemical, anatomical, and morphological traits of plants affect how they reflect light. These traits are important for how plants interact with each other and with their environment. Schweiger says, “Plants with similar traits and species that are close to each other tend to have similar reflectance spectra.”
Using reflected light to figure out what each plant and plant community is like.
The researchers have been working on spectral diversity metrics, and this new study, which was published in Nature Communications, is a continuation of that work. Their indices measure the spectral differences between plants in the same community and between communities in the same region. The difference between communities is called beta-diversity, and the difference within a community is called alpha-diversity.
The National Ecological Observatory Network provided the data for the study (NEON). The network uses standard methods to collect biodiversity and Earth observation data from all over the United States. This information is then shared with the public. Research flights with the NEON imaging spectrometer have pixels that are 1 metre by 1 metre.
Calculations of spectral diversity showed that the size of a plant affects how easy it is to find alpha-diversity. The spectral diversity of forests with closed canopies and big trees matched the diversity of plants found on the ground better than the spectral diversity of open landscapes with lots of small grasses and herbaceous plants. With a spatial resolution of 20×20 metres, spectral beta-diversity, on the other hand, was able to find differences in plant community composition in all ecosystems studied. This pixel size is the same as the size of NEON’s inventory plots for plants.
Almost real-time monitoring of the world’s biodiversity
Image spectrometers for satellites are being made by both the European Space Agency (ESA) and its North American counterpart, NASA. With a pixel size of about 30×30 metres, these are meant to take a picture of the whole world about every 16 days. The results of the study show that these data should make it possible to see changes in ecosystems as they happen. “In the near future, our study will make it easier and more accurate to use satellites to figure out how plant communities are changing. This will make it easier to run targeted field campaigns to figure out the causes and effects of ecosystem change so that people can act in time “says Anna Schweiger. Schweiger says that almost real-time global monitoring of biodiversity is now possible.
Further information: Plant beta-diversity across biomes captured by imaging spectroscopy, Nature Communications (2022). DOI: 10.1038/s41467-022-30369-6
Journal information: Nature Communications
Source: University of Zurich