Earth Day, on April 22, 2021, allows us to reflect on the link that mankind has with the celestial body that carries it. It is also an opportunity to look up at the satellites observing our planet in order to better understand the anthropic transformations it is facing today, especially in the field of tourism.

Observing the Earth with satellite data to rethink the future of tourism

According to the Union of Concerned Scientists, more than 2100 satellites orbit the sky around the Earth and help us to make progress in many scientific fields, to understand our planet and the impact of our interactions with it. In sustainable development, the use of Earth observation satellites as a primary source of data allows us, for example, to measure the impacts of tourism flows and the various interactions of humans with their ecosystems. 

While the effects of mass tourism can be felt on Earth through a decrease in local quality of life identified by various forms of sensory pollution, these effects are also observable from above on a larger scale and reveal the following negative externalities in tourism:

• Excessive consumption of natural resources (energy, food, water…) 
• Pollution by a significant generation of waste that deteriorates ecosystems (for example, according to the 2017 WWF report, more than half of the plastic waste in the Mediterranean Sea comes from tourist flows near the beaches). 
• Soil and water pollution (poor sanitation, seepage, etc.) 
• Destruction of natural ecosystems and the biodiversity they support 
• Air pollution and greenhouse gas emissions (according to Nature climate change, which is based on scientific expertise, more than 8% of the world’s total greenhouse gas emissions can be attributed to mass tourism).

If the impacts of mass tourism in 2020 have been reduced due to the global pandemic, this episode was also an opportunity to question the model we want to move towards tomorrow and with what technology.

The satellite data collected allows us to define key indicators that allow us to evaluate the sustainability of tourism initiatives. It is possible to collect Earth observation satellites of more than 20 relevant measurements including CO2, air pollutants, but also parameters related to the quantity and quality of water, or land artificialization, for example.

This then allows the generation of case studies on a given geographical area through dynamic dashboards that give private or public decision makers the possibility to understand the interactions with the environment and how the actions they implement modify sustainable development. Indeed, like any other economic and social activity, tourism needs data and research to enable and support its successful and sustainable development.

The example of terrestrial breathing seen from the sky

Satellite technology offers raw data but also moments of poetry in images on which it is possible to take an in-depth look at the health of our planet. The image of the Earth breathing through the evolution of its vegetation cover throughout the year is part of these moments, it allows to denote the magic of natural cycles but also the fragility of ecosystems subject to climate change.

For many years, the Earth has been sending signals about its health. Since the mid-1990s, international and civic awareness has been heightened by major global environmental events and has made it possible to include sustainable development among the major challenges of the 21st century. Thus, it is necessary to observe the climatic changes that result from human activity and the transformation of the areas affected by human flows. 

Satellite images, with the observation of the vegetation over a given period of time, enable us to visualize these changes over the long term and to show the disruption of the natural renewal cycles of the Earth.

Since March 2020, confined populations around the world have been spending less time in spaces such as parks or forests, and construction work and deforestation have been largely suspended. It is therefore necessary to question this absence of humans in nature and their impact on the general state of vegetation in certain areas of the world.

How to report on these developments? 

To explain the evolution of vegetation, we use a measure well known to researchers in this field: the Normalized Difference Vegetation Index (NDVI). In order to provide an explanation to as many people as possible, the NDVI is by definition a graphical indicator used to analyze remote sensing measurements, often, as in our case, from a space platform. It allows to evaluate if the observed target contains or not a living green vegetation, observable by a nice emerald coloration present on the satellite images obtained. This is an indicator that is a proxy in the sense that it will not directly describe the changes in coverage but will enable us to create the graphs and curves necessary to understand the phenomenon.

By filtering the data temporally and spatially, the NDVI enables us to obtain the following maps: 

We can see fields and their outlines as well as circular plantations, highlighting the presence of vegetation in green and its absence by the use of a sand-colored band. This allows a vegetation highlighting used later to follow its evolution in time by a succession of images taken at a given moment.

From data collection to modeling a terrestrial breathing

The Amazonian and Central African forests are generally viewed as the lungs of the Earth. However, with these NDVI coloring techniques and an image bank spread over the whole year, it is possible to perceive the real breathing of these real planetary organs. And this is how the poetry of the terrestrial cycles can be highlighted by the use of NDVI computations presented here and images taken from the sky. 

You can perceive the cyclic breath of the Earth on the image below.

The integration of these cycles with the entire terrestrial cycles spread over time allows us to understand the organic mechanism of our planet.

But like any natural cycle, it is possible to disrupt it, and this is unfortunately where several anthropic actions, including tourism, are heading. The forest surface is disappearing more and more every day and the density of the global biomass is decreasing. For example, an increasing number forest-poor areas no longer meet the recommendation of a rate of afforestation greater than or equal to 12% indicated by UNESCO. And despite the lockdown and a suspension of part of the activities, between January and April 2020, in the Amazon, there is a deforestation 55% higher than in the same period of 2019.

Based on these observations, it is necessary to redefine human indicators in order to promote sustainable activities respectful of ecosystems. Measures such as NDVI allow us to highlight the positive or negative impacts on ecosystems on several levels of study revealing some vulnerabilities of our planet.

An Earth Day to call for action

So, on Earth Day, it is still worth emphasizing what satellite images already reveal so well: the responsibility to act more sustainably is key to the climate issues of our century and our choices are crucial. Just seeing these transformations keeps us in the theoretical stage, but choosing, for example, to move around the world by thinking about the planet you are traveling on through sustainable initiatives helps you begin to take action.