Project title: Using satellite data to monitor the health of vegetation in our local area

Team: HRSFC

Hills Road Sixth Form College   Cambridge   United Kingdom   3 Student’s age: 16-17 years old

How can we use colour observable from space to monitor weather-induced changes in vegetation in our area of Cambridgeshire?

In recent years, there has been an increase in heatwaves and unusually hot weather in the summertime in our area, culminating in last year’s record breaking July heatwave [1]. We noticed that this resulted in harm to local plant life with grass yellowing and trees wilting and dying [2]. We feared it could lead to harm to our local ecosystems if the trend were to continue. We wanted to know what could be further understood using satellite imagery. We started this project with the goal to investigate patterns and changes to vegetation observable from space, and whether we could identify any factors behind those.

We used data from the ESA’s Sentinel-2 Satellites [3]. These are a pair of satellites equipped with a Multispectral Instrument (MSI), which measures radiation reflected by the earth in 13 bands. Different wavelengths indicate different surfaces such as water, clouds, plant life, or urban areas. Using the Sentinel Hub EO Browser [4], we analysed images from 2016 to 2022, in a false colour composite, and in the Normalised Difference Vegetation Index (NDVI).

We used the false colour composite built into the EO Browser, which uses Red, Green and infrared radiation to highlight plant density and health. It shows urban areas in grey, dense plant growth in red and sparse plant growth in green [5]. This allowed us to identify where plants were growing healthily and where they were struggling. We also used the NDVI filter, which differentiates between types of vegetation using the chlorophyll in their leaves. Lower values represent earth, shrubs and grassland while higher values represent forested areas [6]. In agriculture, crops with a lower NVDI are generally less healthy.

We produced a range of images using false colour and NDVI in order to establish which colour scheme would best show the changes in vegetation over time in our local area. We compared sets of images on similar dates in the summer of each year. The dates used were as close together as possible, working around cloud cover. We decided to use the false colour images, which showed a clearer contrast between healthy and unhealthy vegetation.

The images are ~20 km across, wide enough to cover Cambridge, surrounding villages and farmland. Images were taken between 17th-24th August for each year. Only six years of data were available, so we cannot draw any complete conclusions from these images alone. However, we were able to identify years in which the vegetation was visibly less healthy, which lined up with a general trend towards hotter summers and particular heatwaves. For example, the UK experienced 3 short heatwaves over the summer of 2022, with a peak recorded temperature of 40.3 degrees Celsius – the UK’s highest ever [7]. The vegetation visibly appears unhealthy from the satellite images, indicating sparse plant growth. This is worrying since there are many crops in the area which are harmed by extreme weather events, as discussed by the government in November 2022 [8].

We can infer that the temperature increases caused by climate change have a significant negative impact on the health of vegetation, particularly crops, in our local area. Our investigation alone does not include enough data to conclude any definitive long-term trends, however we can see connections between high temperatures and plants struggling to grow. In future investigations, it would be good to use data from more years; and to compare historical vegetation health with weather data from the Met Office, such as rainfall and average temperatures, to investigate further correlations between climate change and plant health.

We thought it was important to share our findings with our peers in order to raise awareness about the impact of climate change on our local area. We created a poster to inform others of our project, which was presented at our college’s Eco Fair. We also hope to present our findings to the college’s newspaper and the Environment Society in the future.

References:
[1] https://www.bbc.co.uk/news/uk-england-cambridgeshire-62239990
[2] https://www.cambridgeindependent.co.uk/news/shocking-before-and-after-pictures-show-impact-of-driest-sum-9268984/
[3] https://sentinel.esa.int/web/sentinel/missions/sentinel-2
[4] https://apps.sentinel-hub.com/eo-browser
[5] https://earthobservatory.nasa.gov/features/FalseColor/page6.php
[6] https://eos.com/make-an-analysis/ndvi/
[7] https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2022/2022_03_july_heatwave_v1.pdf
[8] https://committees.parliament.uk/committee/62/environmental-audit-committee/news/174264/to-what-extent-are-global-environmental-changes-affecting-our-food-security/

Download project poster PDF

ESA-poster-for-eco-fair.pdf

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