The European Space Agency
esa-logo
esa-logo
Navigation
world-cereal

Urban nature

Urban nature has a key role to play in building healthy cities.  Access to green areas has been shown to have significant health benefits, both physical and mental, improving the quality of life for the population. Natural land cover helps to reduce heat islands by providing shade and reflecting heat, while parks and other green areas help to better manage floods by absorbing heavy rainfall, as well as increasing urban biodiversity by proving a home for different species. Moreover, a healthy ecosystem has many of the same needs (clean air, clean water, etc) as a healthy human population, so addressing these benefits everyone.

Earth observation (EO) is used to map the extent and condition of green areas within cities, and to observe changes over time. It can also be used to monitor pollution in the environment and to assess its impact on ecosystems. It can also be a powerful tool in studying the complex interactions within the urban environment, for example in assessing how much green areas can contribute to mitigation of heatwaves. Finally, images from space are a powerful tool for raising awareness of issues towards both citizens and policymakers, helping to inspire action.

Urban vegetation

The starting point for urban nature is to map how much vegetation is present in a city, and to assess its condition.  By comparing images taken in different wavebands (optical and infrared) we can assess the type of cover, whether vegetation or built areas. Since healthy plants have a different spectral signature to unhealthy ones, we can also assess the condition of the vegetation.  

Figure: Turin, Italy with false colour to emphasise the vegetation, shown in red, against built up areas, shown in brown and white. Image credit contains modified Copernicus Sentinel data (2018), processed by SEF team.

Air quality

The Po valley is a densely populated and highly industrialised region with mountains to the north and south, creating a basin in which pollutants can be trapped by the weather. The cities in

this region have some of the worst air pollution in Italy, frequently exceeding EU directives for dangerous levels. Accumulation of small particles (PM2.5/PM10) in the lungs can cause serious respiratory problems in humans, and can also damage the vegetation in the area. Satellite data are combined with models and other data to provide high resolution forecasts of air quality across Europe and worldwide.

Image credits: ESA (data source CAMS/ECMWF).

Urban heat

Urban heat islands occur where natural land cover has been replaced by buildings, roads and other artificial surfaces, which absorb and re-emit the Sun’s heat more than vegetation and soil, increasing the temperatures to which city dwellers are exposed.

This image of land surface temperatures in Rome was taken from NASA’s Ecostress instrument, mounted on the International Space Station. The redder the colour, the hotter the land. The image clearly shows the areas of the city most affected by heat, such as the centre and Ciampino airport, where the land temperature reached 35°C. Areas with high vegetation, such as the Appian Way park, were around 10 degrees cooler.

Image credit: Nasa/JPL.

Light pollution

Light pollution in cities can be damaging to both humans and wildlife, disrupting circadian rhythms, disorientating migrating birds, and disorientating nocturnal species. Over time changes in technologies have increased the intensity of light pollution, but also shifted towards whiter and bluer types of lights.

This picture of Milan at night was taken in September 2022 from the International Space Station by Italian astronaut Samantha Cristoforetti. It shows the additional whiteness of the LED lights used in the city centre.

Image credit: NASA/ESA/S. Cristoforetti

Further resources  

Our consortium