Taking the pulse of Earth’s ecosystems
Susan Steele-Dunne has been awarded a NWO Vici grant. She will explore how to monitor the pulse of the Earth’s ecosystems using radar observations. Variations in radar observations from a forest during a day can reveal early warning signs of declining health conditions of the vegetation. An improved understanding of these processes will allow us to make better predictions of how ecosystems will respond to climate change. In the long term, it may even offer opportunities for early interventions.
The key to determining the health condition of vegetation is to measure its water content, according to Susan Steele-Dunne, professor in at Geoscience and Remote Sensing. Microwave measurements are sensitive to the moisture content of a forest. Steele-Dunne and her team have shown that radar measurements in the morning differ from the ones in the evening, and that the variation during the day can reveal the health of vegetation: “If we understand the daily cycle, we can determine the signature of a healthy plant and detect stress in an early stage.” She is also working towards recognising the signatures of specific stressors, such as high temperatures, drought, diseases and pests
At the moment, seasonality of trees can be measured by satellite data. Microwaves detect the moisture and thereby biomass of a forest. Looking into more detail, the observations vary greatly during a day under the influence of different weather conditions. A new satellite mission (named ‘SLAINTE’, Irish for ‘health’) with more frequent observations could reveal the health condition of vegetation.
New satellite mission
Satellites in space now collect microwave data only once every few days. Together with European colleagues, Steele-Dunne is working on a concept for a new radar mission, that can collect data a few times a day. The current understanding of interactions between microwaves and vegetation has been established with today’s satellites in mind. "If we can collect satellite data more frequently, and we want to measure this 'pulse’, we need to revisit our assumptions. We need to take into account faster processes like movements and rain, in order to unravel the signals that reveal the vegetation’s health."
Starting on the ground
One of the biggest challenges is the lack of ground based measurements to test assumptions and develop algorithms. Thanks to her Vici research, she is going to install microwave sensors at ground level and combining them with measurements of water transport. These will reveal how plants store water and how that affects microwave measurements. Furthermore, Steele-Dunne and her team will combine satellite images, radar models and ground measurements to develop the necessary tools to further shape their vision for a future satellite mission.
If we manage to launch a mission and start measuring on a large scale, the impact would be huge. We would be able to predict much better how our ecosystems are affected by humans, and by climate change, and vice versa.
Vici grants
The Dutch Research Council (NWO) has awarded three TU Delft researchers a Vici grant of up to 1.5 million euros each. This will enable them to develop an innovative line of research and further expand their own research group for a period of five years. Vici is one of the largest personal scientific grants in the Netherlands and is aimed at advanced researchers. See the overview article at TU Delft.