Explained | How satellites have become Earth’s new health, nature watchdogs

Satellite data can improve environmental and human health monitoring for three different categories of disease: waterborne, vector-borne, and non-communicable diseases.

By for Dhritiraj Sengupta for 'The Conversation'

Plymouth: Satellite-derived Earth observation (EO) data helps researchers like me unlock new insights into monitoring both environmental and human health.

I’m working with the European Space Agency’s EO4Health Resilience project to integrate information about different types of disease into one digital platform. Due to launch in summer 2025, this project aims to improve accessibility to EO data for medical professionals, support more informed decision-making in public health and hopefully prevent more deaths from disease in the future.

Environmental and animal health are both closely linked to human health. Climate change has a huge influence on these connections, as it can make disease outbreaks such as the 2003 Sars virus and the recent H5N1 bird flu more likely.

By increasing the chance of human-wildlife contact, disruptions like deforestation can increase the risk of disease (like COVID-19) transferring from wildlife to people. Many other factors beyond medicine also determine health, such as sanitation, water supply and farming practices.

The World Health Organisation adopted the One Health approach to inspire a joint response to health threats by connecting efforts by veterinary, public health and environmental sectors.

At a time when governments are struggling to come to grips with the growing costs of healthcare, avoiding outbreaks of infectious diseases is crucial. So, the importance of identifying and monitoring areas of high risk, and of communicating the means of avoiding risks to the public rise to the fore.

Satellite data can improve environmental and human health monitoring for three different categories of disease:

1. Waterborne diseases

There is growing concern about the impact of climate change and human migration. This intensifies the global spread of major bacterial waterborne infectious diseases. EO technology plays a key role in tracking climate change by monitoring big areas over long periods, often in enough detail to spot changes clearly.

Many bacteria, like Vibrio cholerae which causes cholera, thrive in stagnant water. My team worked with the European Space Agency to show that its presence can be modelled using the concentration of chlorophyll found on the surface of bodies of water. Chlorophyll is the green pigment in plants that helps them use sunlight to make their food and grow.

Risk maps for an entire lake can be created using satellite-derived chlorophyll data. Zoonotic diseases that spread from animals to humans such as leptospirosis (a disease caused by Leptospira bacteria) have an animal origin, but reach humans through contaminated floodwater in cities.

Bacteria such as Escherichia coli are often present in sewage pollution and can cause of diarrhoea and gastrointestinal illness. These infections typically occur through activities like drinking or swimming in contaminated water.

A recent study predicts that US cases of non-cholera Vibrio infections could rise by 50% by 2090 compared to 1995. That’s because sea surface temperatures are increasing due to climate change and bacterial populations can grow and spread at warmer temperatures. Satellites could help monitor those temperature changes and therefore identify places most prone to outbreaks.

One recent report highlights the value of satellites studying waterborne diseases. The ability to measure and monitor water quality across large areas makes it much easier and quicker to deliver near real-time information.

2. Vector-borne diseases

Vector-borne diseases, such as the West Nile virus and malaria, pose significant global health threats. They are transmitted by mosquitoes and can lead to severe neurological diseases. Vector-borne diseases are a leading cause of morbidity and mortality, particularly in tropical regions.

My colleagues in Italy used EO data to unlock new insights about the transmission of West Nile virus. Models based on satellite data that showed temperature, humidity and vegetation – all of which influence mosquito populations and disease transmission patterns – can help forecast the next outbreak.

The malaria atlas is a collaborative project that involves scientists from around the world. By collating EO data, mosquito breeding sites can be mapped, while climate change can be tracked as it affects the habitats that disease-carrying mosquitoes live in. Maps like this enhance the effectiveness of public health strategies by pinpointing where best to focus efforts and resources to control and prevent the spread of these diseases.

3. Non-communicable diseases

Non-communicable diseases, such as cardiovascular diseases exacerbated by heatwaves, rank among the top global causes of death. Prolonged exposure to extreme heat can strain the heart, increasing risks of heart attacks and strokes. So, isolating locations most at risk of heatwaves could help target aid and reduce the risk of widespread heatstroke and other conditions.

Environmental factors like urbanisation, climate change and air pollution amplify health risks. Several EO projects funded by the European Space Agency use AI and satellite data to map land surface temperatures, greenhouse gas emissions, green spaces, rivers and lakes.

For example, poor air quality caused by high levels of emissions in urban areas can lead to respiratory diseases such as asthma and chronic obstructive pulmonary disease. Long-term exposure to pollutants like fine particulate matter known as PM2.5 and nitrogen dioxide may increase the risks of cardiovascular diseases, lung cancer, and even premature death.

Mapping air quality using satellite data helps identify particulate pollution hotspots. This supports targeted interventions to improve public health.

In the future, satellites could track plastic pollution in oceans. Marine life consumes plastic particles that humans ingest through seafood. Chemicals present in plastics can lead to hormone disruption in humans and may increase cancer risk or immunity, for example. So tracking pollution distribution around the globe could identify sources and the places where people and wildlife are at most risk of exposure to chemical contaminants like those in plastic.

(The author is an Earth Observation Scientist with the Plymouth Marine Laboratory)