Scientific Writing

Abstract

For the past few decades our planet is experiencing constant change, which mostly derives from human activities, like the excessive burn of fossil fuels, urbanization and deforestation. Earth Observation (EO) satellite data allow for retrieving an overview of the vast surface of the Earth and gain insight about the different processes that occur on it. The purpose of this paper is to provide an overview about the contribution of satellite EO in the effort of conserving the environment from both natural and anthropogenic threats. The paper analyses three fields of EO studies that contribute to environmental protection. Time series analysis is a well-known method that reveals changes that have occurred throughout time and space. Large EO data availability allows for the study of natural phenomena, like ocean currents, and for gaining insights about how they are related with each other and their impacts on the environment. Monitoring disasters, such as wildfires, is another field that EO can be utilized, from surveilling them while they occur, to evaluating their impacts and assist in designing restoration plans for affected areas. Lastly, EO can add to the creation of robust models and forecast systems and help communities prepare for extreme phenomena, like floods, or even prevent them by taking proper measures. While EO is already a valuable means, future technological advancements and the addition of new satellite sensors, will lead to an ever deeper understanding of the processes that occur in our planet and assist to its protection.

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Introduction: Space and Earth Observation

Space, more specifically geographical space, is a fundamental element for the science of geography. It is often expressed as a “synergic system” that contains different objects (Mazúr, E. and Urbánek, J., 1983) from rivers and forests to highways and cities. These objects are somehow related to each other, simply because they all exist in the same “space”. Space can also be perceived as a “container” where different processes take place and different elements interact with each other, so studying it is critical for identifying these different processes. In the current era of constant change, from climate change, increased soil erosion and water reserve decrease, to socio-economic shifts and urbanization, it is critical to understand processes and changes in our planet’s surface (Kuenzer, Dech and Wagner, 2015, p.2). A lot of these changes, that negatively affect the physical environment, are ultimately caused by human activities, like burning of fossil fuels and deforestation. In order to diminish the consequences of these negative effects or restore the environment after they have occurred, the practice of environmental conservation has been introduced, which aims at preserving the environment and the natural resources. Protecting the natural environment is crucial not only for biodiversity itself, but also for the future of humanity, since it provides us 2 with many necessary ecosystem services, which are currently threatened by human activities. The purpose of environmental conservation is to restore this ecological balance, leading to a more sustainable future. Since space is so vast, modern technology can contribute to a better understanding of it. An example of such technology is Earth Observation (EO), which is the gathering of information about planet Earth’s physical, chemical, and biological systems typically using data captured from satellite and airborne sensors (EU Science Hub). It is used to monitor and assess the status of, and the changes that occur in, the natural and manmade environment, usually without having to visit the specific place, thus making the process significantly cost and time effective. Earth Observation satellites orbit the earth and carry different instruments dedicated to discrete applications, such as visible, near-infrared, and thermal sensors (passive sensors), radar (SAR), LIDAR, and Microwave radiometers (active sensors), which gather information about our planet (JAXA). Respectively, EO satellite data provide an overview of the earth’s surface and insights about different processes. Since Satellite Earth Observation allows us to view “space” as a whole, study its diverse components and the different mechanisms and phenomena that take place in it, it can eventually contribute to the conservation of the physical and manmade environment from both natural and anthropogenic causes.

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Detecting changes

Earth Observation can add to the understanding of natural processes that take place in space. For 50 years, satellites have been collecting continuous measurements about the Earth's surface, while more satellites are launched every year carrying both passive and active sensors and allowing us to monitor the surface of the Earth. Using time series of satellite data, we can revisit space in the past, observe changes and quantify the impact of these changes on the environment. This process is called change detection and it involves the use of multi-temporal datasets (Mishra et al. 2017). Since many satellite observations are required for time series analysis, free and open access to satellite earth observation data has benefited such applications (Kuenzer, Dech and 3 Wagner, 2015, p.2). For example, by studying coastal areas throughout time, we are able to detect changes in the coast and reveal useful insights about the causes of coastal erosion and deterioration. The causes can either derive from natural processes or manmade constructions. If the later applies, such studies can assist policy makers to take measures and create plans for the preservation of the coastal zones (Ragia and Krassakis, 2019).

Another change detection paradigm could be the monitoring of water reservoirs, which hold not only an ecological value, but are also essential for human consumption and agricultural use. An example of such change is visible in Figure 2, where two lakes, Urmia Lake and Aral Lake, have been affected by an enormous decrease in their water levels. A decrease in water level can affect human communities residing in close areas (Khorshiddoust et al., 2022). Again, this is ultimately a human-induced issue, since the water level decreased because of excessive usage of water for irrigation (Britannica). By utilizing satellite observations, we can monitor natural phenomena and identify how they evolve in space, as well as their impact both on the physical and human environment in a negative or positive way. An example would be the monitoring of natural events like El Niño, which can affect the marine environment, the climate, and ultimately human populations, causing floods or drought. El Niño has not been extensively studied yet, especially using satellite Earth Observation data, and its specific effects in different regions remain unknown. Thus, studying the phenomenon is important for policy makers to take action against its impacts on populations and for the development of information technology infrastructure (Eboy & Kemarau, 2021). All in all, Earth Observation may enrich our knowledge about why specific events and phenomena occur in specific spaces as well as how these processes are related. The ultimate objective is to utilize this knowledge for the sustainable development of these areas and to protect fragile ecosystems (Khorshiddoust et al., 2022).

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Disaster monitoring and assessment

Through Earth Observation technologies, and especially by using satellite data, it is possible to study and analyze natural and anthropogenic disasters and offer aid to vulnerable ecosystems and communities. Satellite sensors can quantify physical geographic phenomena 4 including movements of the surface of the earth, water and fires. EO gives us the opportunity to assess disasters and their impacts in the space they occurred. Especially due to increases in data acquisition rates and improvements in the sensors spatial, temporal and radiometric resolution, assessment of hazard and disasters in near real-time has been improved (Gillespie et al., 2007). For example, it is possible to monitor the spread of wildfires and study how the affected environment recovered. In the past years, number of wildfires has extremely increased because of anthropogenic climate change. EO satellite data constitute a useful tool for post-fire studies of vegetation dynamics, both for large and smaller areas. By monitoring the recovery of natural environments after such disasters, valuable information can be retrieved regarding forest recovery processes and repopulation areas, which can help policy makers, planners and foresters determine focus areas for ecosystem restoration (Filipponi & Manfron, 2019). This also applies to manmade disasters, like industrial accidents, where EO imagery can reveal affected infrastructure and buildings. An example could be the fatal industrial accident that took place in the port of Beirut, Lebanon in 2020, where satellite data were utilized to assess damages (CEMS). Emergency response systems and platforms can be established, which will provide impactful insights for policymakers and emergency responders as well as civilians. In the beforementioned industrial disaster, the Copernicus Emergency Management Service (CEMS) of the European Commission was activated, to rapidly assess the aftermath of the incident and continued monitoring the event several months after to assist with measurement implementation (CEMS). With more information, better decisions can be made, and effective action plans can be created which will benefit human populations and ecosystems impacted by a disaster.

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Forecasting and modeling

Last but not least, Earth Observation techniques can contribute to the prediction of natural events and disasters. Although forecasts for meteorological parameters are well established, the use of EO satellite data for modelling phenomena on the Earth’s surface is still limited, but progress is continuously been made. By applying different modeling workflows and fusing data (for example satellite imagery and data, Digital Elevation Model products, demographic data, etc), the behavior of divergent phenomena can be forecasted, like Land Surface Temperature and vegetation dynamics (Koehler & Kuenzer, 2020). Even more importantly though, dangerous phenomena and extreme weather events, such as floods, can be modeled, therefore making it possible to take precautions against these possible disasters and even save human lives. Floods are considered the most catastrophic natural disaster, that not only alter natural ecosystems and impact infrastructure, but also cost human lives. EO satellite data can be used as an input for hydrological models and for validating their results (Munawar et al., 2022). Advancing technologies, such as Machine Learning and Neural Networks (NNs), have made forecasting faster and more accurate, thus improving our response during emergency situations (Koehler & Kuenzer, 2020). Neural Networks can be used for modelling countless physical parameters, one of which is Sea Surface Temperature (SST). SST influences our planets entire ecosystem, from energy balances to precipitation distribution, making its precise prediction key for environmental protection (Jia et al., 2022). In today's world of constant change, being able to accurately predict and model natural hazards can be a critical asset in conserving our habitat.

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Conclusions

Space encompasses several diverse components and processes, both natural and manmade, which depend on and interact with each other. Earth Observation, and specifically satellite EO, can be utilized to study these elements, allowing us to navigate continuously not only through space, by enabling us to cover large areas of the world, but also through time. EO data allow us to study the evolution of natural processes through time and the impact of human activities on the environment. Another important application of EO is the monitoring of natural and anthropogenic disasters and the development of disaster risk management plans, which can ultimately contribute to the preservation of the Earth’s systems. By introducing modeling technics and data fusion, together with modern technology, such as deep learning, EO data can be beneficial in the effort of mitigating the impacts of a natural hazard or disaster. In general, the implementation of EO workflows, may result into useful information for authorities, policy makers and emergency responders, thus diminishing the effects of extreme phenomena. All in all, EO is already a valuable tool and continuous improvements, and technological breakthroughs make it an integral part of understanding and conserving the space we live in.

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