Can we monitor plant biodiversity from space?

Monitoring plant biodiversity from space using satellite data will soon be feasible, according to a new study published in the journal Nature Communications.

New ways to accurately and efficiently monitor biodiversity are increasingly important to support efforts to protect and restore ecosystems affected by climate change and other threats. Many current biodiversity monitoring techniques require sending humans out into an environment to collect samples and data, making monitoring expensive and labour-intensive.

A team led by Anna Schweiger from the University of Zurich, Switzerland, and Etienne Laliberté from the University of Montreal, Canada, has demonstrated that a key measure of plant biodiversity can be gleaned by analysing data collected by Earth observation satellites. Their dataset was drawn from the National Ecological Observatory Network (NEON), which collects standardised biodiversity and Earth observation data from around the United States.

“With our study, we hope to contribute to the future detection of changes in species composition of our Earth’s ecosystems from space,” says Schweiger. “The goal is to provide evidence-based guidance for policy measures to protect species and mitigate negative consequences of biodiversity loss.”

The researchers used a technique called image spectrometry to measure the reflectance of light as captured by satellites, and translate this into the shortwave infrared range of the electromagnetic spectrum. Plants have different reflectance values based on various characteristics, such as their shape and size and chemical properties.

“Plants with similar traits, as well as closely related species, therefore tend to have similar reflectance spectra,” Schweiger explains.

By calculating the spectral diversity of these values, the team showed that accurate measurements of beta-diversity – the differences between plant communities – could be obtained from the satellite data across ecosystems from the Arctic tundra to tropical rainforests, at a resolution of 20 x 20 metres.

Measurements of alpha-diversity, or the diversity of different plants within one ecological community, varied in accuracy depending on the environment. Estimates of alpha-diversity from satellite data were more accurate in forests with closed canopies – less so in more open landscapes.

Both NASA and the European Space Agency (ESA) are planning to deploy new satellite-based image spectrometers which will image the entire planet about every 16 days. Using the techniques described in the new study could allow monitoring of plant biodiversity changes around the world almost in real time.

“Our study will help to effectively and reliably determine changes in plant community composition via satellite in the foreseeable future,” says Schweiger. “This will facilitate targeted field campaigns to assess the causes and consequences of ecosystem change, allowing stakeholders to react in due time.”