Satellite monitoring of biodiversity advances to protect threatened ecosystems

Diversity of plant species in four different ecosystems represented as spectral variation. Credit: Anna Schweiger, Etienne Laliberté

Internationally comparable biodiversity data is needed to protect threatened ecosystems, restore destroyed habitats and counter the negative effects of global biodiversity loss. However, current biodiversity monitoring is laborious and costly. In addition, many places in the world are difficult to access.

Biodiversity monitoring from space possible via satellite

Anna Schweiger from the Remote Sensing Laboratories of the Department of Geography at the University of Zurich (UZH) and Etienne Laliberté from the University of Montreal have now shown that plant biodiversity in ecosystems ranging from arctic tundra to tropical forests can be assessed from reliably using image spectrometry. “With our study, we hope to contribute to the future detection of changes in the species composition of our Earth’s ecosystems from space. The aim is to provide evidence-based guidance for policy measures to protect species and mitigate the negative consequences of biodiversity loss,” says first author Anna Schweiger.

Imaging spectrometers measure the reflectance of light from the visible to the shortwave infrared of the electromagnetic spectrum. The reflectance of plants is determined by their chemical, anatomical and morphological characteristics, which are important for the interactions between plants and with their environment. “Plants with similar traits, as well as closely related species, therefore tend to have similar reflectance spectra,” says Schweiger.

Using reflected light to assess characteristics of individual plants and plant communities

The current study is a continuation of the researchers’ work on spectral diversity measurements. Their indices calculate the spectral variation between individual plants within communities and between communities within a region. Diversity within communities is called alpha diversity, while diversity between communities is called beta diversity.

Data for the study come from the National Network of Ecological Observatories (NEON). The network uses standardized methods to collect biodiversity and Earth observation data across the United States, which is then made publicly available. NEON Imaging Spectrometer data collected during research flights has a pixel size of 1 × 1 meter.

Spectral diversity calculations showed that the detection of alpha diversity depends on plant size. Calculated spectral diversity in forests with closed canopies and tall individual trees corresponded better to field-determined plant diversity than calculated spectral diversity in open landscapes dominated by small herbaceous and grassy plants. Spectral beta diversity, however, captured differences in plant community composition across all studied ecosystems based on a spatial resolution of 20 × 20 meters. This pixel size corresponds to the size of the NEON vegetation inventory plots.

Monitor global biodiversity in near real time

The European Space Agency (ESA) and its North American counterpart " data-gt-translate-attributes="[{" attribute="">Nasa are currently developing satellite image spectrometers. These are intended to image the entire globe approximately every 16 days with a pixel size of approximately 30×30 meters. The results of the study show that these data should be able to detect changes in the ecosystem as they occur. “Our study will help to efficiently and reliably determine changes in satellite plant community composition for the foreseeable future. This will facilitate targeted field campaigns to assess the causes and consequences of ecosystem change, enabling stakeholders to respond in a timely manner,” says Anna Schweiger. According to Schweiger, global biodiversity monitoring – almost in real time – is now at your fingertips.

Reference: “Plant beta-diversity across biomes captured by Imaging Spectroscopy” by Anna K. Schweiger and Etienne Laliberté, May 19, 2022, Nature Communication.
DOI: 10.1038/s41467-022-30369-6