Tribune | “Importance of satellite images in environmental analysis and protection”

As expected, COP 27 in Sharm El Sheikh in November 2022 showed some promise. Political, industry and academic leaders have set goals to promote sustainable agriculture, prevent deforestation, protect our oceans, eradicate illegal mining… But understanding exactly what happens when remote or hard-to-reach ecosystems access the blue planet (that’s over 196.9 million square kilometers) may seem like a feat.

Fortunately, recent advances in satellite technology now allow this feat to become a reality. Currently, commercial satellites can capture very detailed images with a resolution of up to 30 cm and a diameter of tens of kilometers. They are also capable of extremely accurate geotagging – up to 3.5 meters – which ensures that everything visible in the image is easily mapped to a matching set of coordinates. How is satellite imagery an important tool in environmental analysis and protection during a climate emergency?

Monitoring of waters to better protect them

Our seas and oceans are strained by climate change. Rising sea levels and rising water temperatures have negative side effects such as toxic algal blooms and coral bleaching. Overfishing and pollution are also driving entire species to extinction.

Covering almost three-quarters of the Earth’s surface, the sheer size of our seas and oceans makes it nearly impossible to gain a comprehensive understanding of marine ecosystems on land, or in this case, waters. Using satellite imagery is the only way to achieve this.

Marine observation is one way satellites help protect the health of our oceans. The law requires commercial trawlers to be equipped with automatic identification system transponders. However, offending vessels often disable these systems to avoid detection, leaving authorities in the dark about their true activities. Satellite Earth observation can fill this gap, allowing governments and NGOs to monitor illegal fishing hotspots and identify offending vessels.

In addition to monitoring illegal activities at sea, satellite imagery allows us to better understand the state of the coast, assess the depth, quality and clarity of the water. Images can be retrospectively colored by combining multispectral data, revealing hidden information that is invisible to the naked eye.

“Deep Blue” spectral band used to estimate water depth and improve navigational safety – Persian Gulf, February 2021, Pléiades Neo.

Promoting more sustainable agriculture

The use of new multispectral channels on land also promotes sustainable agriculture and enables accurate crop analysis. For example, in the figure below, spectral data processing reveals the level of chlorophyll in vegetation. Monitoring leaf chlorophyll content is important to assess plant nitrogen status over time and allow farmers to take corrective actions to improve crop health.

Chlorophyll content of leaves – Mérida, Mexico, Pléiades Neo.

Interestingly, by combining the spectral richness of the image with the modeling of crop properties, it is possible to create maps of biophysical parameters that allow characterizing the state of vegetation. For example, Figure 3 uses the same image as Figure 2 to measure the leaf area index, that is, the amount of leaves per unit of land. This information will help farmers make more informed decisions about specific crop needs within their plot, allowing for less input and more sustainable water use.

Leaf area index – Mérida, Mexico, Pléiades Neo.

Help prevent natural disasters

Natural disasters are occurring more frequently due to climate change, even in regions previously unaffected by extreme weather events.

Arguably, there is no alternative to ground observation for effective data collection during natural disasters – especially when assessing the situation on the ground is deemed too dangerous. It should be noted that recent advances in satellite technology have dramatically increased the flexibility of using satellites. Emergency requests can now be processed within 30 minutes, greatly increasing the usefulness of satellites in crisis situations and natural disaster scenarios.

Take the example of the hurricane that hit Mananjari, Madagascar earlier this year. Thanks to satellite images, local authorities and NGOs were able to quickly identify which areas were flooded in order to send aid and identify safe access routes.

Flood monitoring – Mananjari, Madagascar, February 2022, Pléiades Neo

After the hurricane and flooding, officials again used satellite images to assess the extent of the damage. For example, by comparing images 7 and 8, they were able to identify damaged buildings and plan reconstruction accordingly.

Figure 1: Mananjari, Madagascar, June 2021, Pléiades.
Figure 2: Mananjari, Madagascar, February 2022, Pléiades Neo.

Which one is used for satellite imagery in the future?

We are at a major turning point in the use of satellite imagery. Thanks to recent technological developments, the quality of images is now high enough to reveal the finest details. At the same time, advances in big data and artificial intelligence make it possible to process and analyze large amounts of data to detect trends and anomalies.
Governments, law enforcement, NGOs, and businesses must now use this technology to create “collaborative” use cases that can be used proactively over time, rather than just reactively. . We can cite here Starling, a fully digitized deforestation monitoring service used by major global players in the fashion and food industries. The Starling online portal combines satellite images of forest cover with user-submitted supply chain data, such as contact information for palm oil, cocoa, paper and coffee suppliers. By using both satellite and supply chain data, companies can encourage their suppliers to combat deforestation and choose more sustainable alternatives.

This approach has great potential and can be applied in other fields as well. To help anticipate the impact of natural disasters such as landslides, avalanches and volcanic eruptions by carefully monitoring the evolution of geographical areas particularly at risk. Satellite data can also be used by governments to support the development of sustainable cities, such as identifying and preventing urban heat islands or ensuring that their development excludes flood-prone areas by measuring elevation levels.

In general, the possibilities of using satellite data for environmental protection and analysis are endless. Their success will depend on public-private cooperation, ensuring that stakeholders feel empowered to work with satellite imagery.