Mapping and monitoring of the marine environment has been consistently reliant upon space-based technologies (Johannessen et al., 2006). Particularly tools targeting monitoring of human activity in the marine domain, marine resources such as marine protected areas and fish stocks, as well as marine environmental conditions, are extensively utilised by regulatory actors (Desaubies, 2006). This article aims at providing a set of examples of space-based technologies that are used for monitoring of different aspects of the marine domain, illustrating the wide range of available relevant applications.
Among the most popular and widely available technologies are GNSS-enabled vessel tracking systems. One such system is the Satellite-based Automatic Identification System (S-AIS), a marine vessel tracking system utilised by vessel traffic services. It collects signals from marine vessels to determine their identification, location, speed, and course through satellites and supports many functions, from navigation, accidents and search and rescue to marine infrastructure monitoring (Cervera, Ginesi and Eckstein, 2011). In similar fashion, the Long Range Tracking and Identification (LRIT) system tracks and monitors mainly cargo ships, as well as passenger vessels and mobile offshore oil rigs to share necessary information relevant to marine safety (Popa, 2011).
Another system, predominant in the European Union (EU), is the Vessel Monitoring System (VMS) which monitors fishing activity (European Commission, 2003). The use of VMS allows for better monitoring and enforcement of fisheries-related regulation, keeping track of vessel movement and patterns in routes and stationary activities, giving a thus clear indication of entrance in protected areas and use of diverse fishing gear. Since 2004, its use has been established as a prerequisite for large and medium-scale fishing vessels operating within the European territorial waters, supporting enforcement of regulation on Illegal, Unreported and Unregulated (IUU) fishing practices and tracking of catches (European Commission, 2003). See an example of using satellite-based surveillance for IUU in Figure 1 below.
Apart from GNSS, Earth Observation (EO) is also utilised extensively in the marine domain, mostly for identification of marine and coastal environmental condition changes and marine accidents such as oil spills and capsized ships, helping thus to minimise impacts on marine species and habitats. Furthermore, a combination of GNSS and EO can be a reliable source of information regarding marine accidents, particularly location-wise, and can therefore be essential in saving human lives.
EO data is also extensively used in environmental monitoring. In the case of oil spills for example, EO data, and in particular radar data, are routinely used to create maps to monitor the spread of oil spills. Such data sources are invaluable resources for authorities involved in clean-up efforts as they provide data in near-real-time, enabling more efficient and effective approaches to oil spill mitigation initiatives, protecting thus vulnerable ecosystems and valuable commercial resources (fish stocks) (Maxwell et al.,2015). A further contribution to marine environmental monitoring is relevant to modelling. Modelling accurate predictions of change in the marine environment such as sea level rise or ocean acidification require vast amounts of input data. Satellites are a critical resource to this end, because they constantly monitor meteorological and other environmental conditions and therefore provide important information input to predictive models (Ó Tuama and Hamre, 2007).
Nevertheless, space-based technologies for the collection of scientific information should not be considered as restricted to the scientific community, as they have great potential to enable contributions by the general public, while raising awareness about the cause of marine environmental protection. Initiatives based on the idea of citizen science have been widely established across the different subdisciplines of marine conservation, supporting science and policymaking at limited to zero cost.
Applications like Zooniverse allow the general public to generate data for scientific research. They allow to monitor phenomena for which it is difficult to collect data, either due to financial limitations or due to requirements of very large sample sizes. The topics of projects to which citizen science adds relevant and considerable contribution range from location and classification of different seaweed species to fish migration and from jelly blooms to red tide monitoring and anything else in between. An illustrative example would be sightings of marine mammals. Citizens with GNSS-enabled devices can report the exact location of a mammal sighting by geotagging, along with other relevant information (e.g. photographs) that would enable the identification and further tracking of the sighted individual in real time.
Of course, citizen science can work only complimentarily to other established methods of monitoring. Space-based technologies play an important role also in mainstream data collection for marine species monitoring. The most common application is GNSS tracking: trackers are fitted on marine animals or released in the study area to track marine migration routes and or identification and location of pre-registered individuals or groups (schools, pods). Furthermore, EO imagery can be used for population and habit monitoring, including mapping of feeding areas and nurseries.
The use of space-based technologies for monitoring of marine areas has proven to be versatile in the objectives that it may fulfil. In 2015, EO and GNSS were used to locate and provide photographic evidence of a human trafficking case within a fishery operation off the coast of Indonesia. Large-scale fisheries operating in the high seas are a common setting for employment of human trafficking practices. Fisheries operators will often trick individuals into boarding the vessel by baiting them with employment opportunities, or kidnap children, and then detain and coerce them into forced labour (Sylwester, 2014; Rahman, 2011). Banned from any contact outside the vessel, the trafficking victims are effectively imprisoned on the vessel. The vessel remains at sea at all times and in order to land the catches, ‘transfer’ vessels approach the fishing boat and offload the fish in predetermined locations offshore. In case regional or local authorities have information about a potential handover, they can utilise EO satellites to provide photographic evidence by scanning the marine area where the handover is supposed to take place. In the 2015 case in Indonesia, this method assisted the local authorities to rescue 2000 trafficked individuals detained in such a fishing vessel.
Space-based technologies are an invaluable tool for marine monitoring, with great potential to contribute to sustainable policy- and decision-making. Access to and adoption of such technologies are at the forefront of the quest towards the achievement of sustainable development globally, particularly when seen through the lens of the 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals. SDG14: Life Below Water calls specifically for action regarding the development and transfer of new technologies to improve marine environmental conditions and promote sustainable use of the oceans (United Nations, 2015), indicating that increased accessibility to space-based technologies can contribute the fulfilment of many societal needs with regard to the marine environment.