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In 2024, the Coast Guard Aircraft of the Institute of Natural Sciences documented 4 cases of operational marine pollution by ships. In addition, suspicious sulphur and nitrogen values were measured in the exhaust plumes of 31 and 59 ships. Other activities included broader maritime surveillance in support of the Coast Guard, participation in international operations and marine mammal counts.

Overview of surveillance flights

In 2024, a total of 220 flight hours were performed over the North Sea as part of the national aerial surveillance programme. This programme is organised by the Scientific Service MUMM (Management Unit of the Mathematical Model of the North Sea) of the Institute of Natural Sciences, in collaboration with the Ministry of Defence.

The biggest effort (177.5 hours) was dedicated to national flights, with no less than 161.5 flying hours in the context of the Belgian Coast Guard. This included 118.5 hours for maritime surveillance under the International Convention for the Prevention of Pollution from Ships (MARPOL). Of these, 69 hours were dedicated to monitoring for discharges of oil, other harmful substances, and garbage, while the remaining 49.5 hours were spent monitoring sulphur and nitrogen emissions from ships. Another 43 hours were used for fisheries control on behalf of the Flemish Fisheries Service, including aerial support during a marine pollution response exercise. In addition, 16 hours were dedicated to marine mammal monitoring.

Internationally, 42.5 hours were flown in the framework of the Bonn Agreement, which provides for international cooperation among North Sea coastal states in the fight against marine pollution. This included a Tour d’Horizon (TdH) mission for the monitoring of oil and gas installations and a multi-day monitoring campaign at the border of the ship emission control area off Brittany (France). Finally, 23.5 hours were flown in the context of the European research project CINDI-3, in collaboration with the Belgian Institute for Space Aeronomy (BIRA).

Spills from ships

No oil pollution was observed in the Belgian part of the North Sea in 2024, maintaining the declining trend seen over the past 34 years.

However, 4 operational discharges of harmful substances other than oil (MARPOL Annex II) were observed, each time without a polluter in sight. This made it impossible to determine which specific type of liquid was discharged into the sea.

Unlike oil spills, discharges of noxious liquid substances remain a common problem. Until 2022, an increasing trend in observations had been noted, which was confirmed by other North Sea countries. 2023 marked the first year in the past decade with a decrease, a trend that appears to continue in 2024. However, it is still too early to draw firm conclusions. The fact that some discharges are legally permitted does not change the reality that they may have a negative impact on the marine environment. Continued monitoring by coastal states is important, both to map potential problems at sea and to encourage legal updates where necessary.

No violations of MARPOL Annex V, which concerns the discharge of garbage and solid bulk substances into the sea, were observed in 2024.

Oil pollution in ports

On 14 March 2024, the Coast Guard Aircraft detected a weathered oil slick in the port of Antwerp, with no polluter nearby. On 4 June, several oil slicks were observed in the same port, possibly a historical pollution released during dredging operations. Shortly thereafter, on 7 June, oil was again observed. After contacting the port authorities, the pollution was found to be the result of an overflow of heavy fuel oil during a bunkering operation. In the following days, several flights were conducted over the port to monitor the situation and assess the effectiveness of the pollution response actions.

Monitoring of sulphur and nitrogen emissions

Belgium continues to be a frontrunner in the international fight against air pollution from ships through the use of a sniffer sensor on board the Coast Guard Aircraft (monitoring and enforcement of MARPOL Annex VI). This sensor allows for real-time measurement of various air pollutants in the exhaust plumes of vessels.

Sulphur measurements have been part of the programme since 2016 and aim to monitor compliance with the strict sulphur limits for ship fuel within the North Sea Emission Control Area. In 2024, 31 out of 743 ships inspected showed suspiciously high sulphur values.

Since 2020, with the addition of a NOx sensor, the aircraft has also measured nitrogen compound (NOx) concentrations in ship exhaust plumes. These measurements support the enforcement of stricter NOx limits applicable since 1 January 2021 in the North Sea Emission Control Area. In 2024, suspicious NOx values were observed in 59 out of 735 ships.

All suspicious cases were reported to the competent Belgian and European maritime inspection services for follow-up and further checks in port.

In 2021, a black carbon sensor was added to the sniffer set-up. This sensor measures black carbon emissions, an indicator of soot levels in ship exhaust. Emissions of 451 vessels were measured in 2024. Preliminary results show that ships emit significantly more soot at sea than previously estimated.

Extended maritime surveillance

Within the framework of the Coast Guard, the aircraft also contributes to broader missions of maritime enforcement and safety. MUMM’s aerial operators regularly report violations of navigational rules and the mandatory use of AIS (Automatic Identification System) to the Coast Guard Centre, and monitor potential breaches of safety perimeters around certain infrastructure such as wind farms or aquaculture farms.

In 2024, 11 vessels were observed without an active AIS signal, all of them fishing vessels. Additionally, 26 navigational violations were observed — a significant increase — mainly involving vessels sailing in the wrong direction (ghost sailing) or anchoring in shipping lanes. These observations were systematically reported to the Directorate-General for Shipping (FPS Mobility and Transport) for follow-up.

Last year, 3 violations related to intrusions into sea safety perimeters were also reported to the competent authorities. This is in line with 2023 figures but significantly lower than in previous years. A likely explanation is that restricted areas such as the aquaculture farm off Nieuwpoort and the calibration zone near Ostend are now more widely known and respected by the maritime community.

Finally, in close coordination with the Maritime Information Crossroad (MIK) , the aircraft monitored 4 suspicious activities in or near Belgian sea areas, 3 of which involved Russian vessels.

Monitoring of marine mammals

In April, August and November 2024, the Institute of Natural Sciences carried out seasonal surveys of marine mammals. Respectively 109, 21 and 69 Harbour Porpoises were observed along the flight paths. Scientific extrapolation suggest population estimates of over 5,200 animals in April, over 1,000 in August, and over 3,300 in November within Belgian waters.

Seals were also regularly observed: 3, 10 and 18 in the respective months. The April survey was particularly noteworthy, with rare sightings including a Minke Whale and a group of five White-beaked Dolphins.

International missions

In July, a multi-day campaign was held at the edge of the Emission Control Area near Brest, resulting in 21.2 flight hours. During 5 days, emissions from 189 ships were monitored. Fourteen vessels exceeded sulphur limits, and 4 showed excessive NOx emissions. All observations were reported to the French authorities and the relevant European ports of call and were entered into the European inspection database Thetis-EU.

In September, the annual international ‘Tour d’Horizon’ mission was carried out under the Bonn Agreement (21.3 flight hours), focusing on pollution from oil and gas installations in the central North Sea (Dutch, Danish, British and Norwegian waters). The aircraft detected a total of 8 oil spills — a low number compared to previous years, likely due to poor weather conditions and rough seas causing rapid dilution of oil in water. Seven of the eight spills could be directly linked to an oil platform. All observations were systematically reported to the competent coastal states for follow-up in accordance with international procedures.

The CINDI-3 campaign was held for the third time in Cabauw, the Netherlands. More than 100 participants from 16 countries collaborated with the goal of comparing scientific measuring instruments for nitrogen dioxide, ozone, aerosols and other gases. Measurements were taken from land, air and space.

A key part of the campaign was the use of the Coast Guard Aircraft to measure air quality over Cabauw and the ports of Rotterdam and Antwerp. Combining airborne data with other instruments provided valuable information for validating satellite observations of air pollution.

A new horizon?

While 2024 was another successful year in terms of the results achieved by the North Sea aerial surveillance programme, it should be noted that the coastguard aircraft is an ageing platform that will soon be 50 years old. Its replacement is necessary to ensure the continuity of the increasingly delicate operations entrusted to Belgium as a coastal state in an increasingly complex maritime and international context. Without this, it is likely that Belgium will no longer have a suitable aerial surveillance platform and will therefore no longer be able to fully meet its national and international commitments to environmental protection, safety and security in the North Sea.

Long ago, the Flat oyster was ubiquitous in the southern North Sea. But due to overfishing, pollution and diseases, this native species almost completely disappeared from our country. Today, there are signs that the Flat oyster has begun a cautious recovery. This is demonstrated by finds in unexpected places, such as in ports and offshore wind farms.

The fact that the Flat oyster (Ostrea edulis) has been found again in Belgian waters can certainly be called a sensation. After decades of absence, marine biologists have found living specimens and empty shells of Flat oysters on all kinds of human infrastructure, including scientific instruments. Flat oysters are now also being found in port areas such as Zeebrugge and Ostend.

In addition, offshore structures, such as the steel foundations of offshore wind turbines, provide new habitats for oyster larvae to attach. Beachcombers have found live specimens and fresh shells of Flat oysters washed up on the beaches of the western coastal zone.

Francis Kerckhof and Thomas Kerkhove of the research group ‘Marine Ecology and Management’ (MARECO) of the Institute of Natural Sciences summarize the recent finds in an article in ‘De Strandvlo’, the magazine of the Belgian Beach Working Group (Strandwerkgroep België), and examine possible explanations. What is striking is that the new finds seem to be at least partly of wild origin. A comeback to the rhythm of the sea.

Why are ports and wind farms interesting for oysters?

The modern seaport has surprisingly become a suitable habitat for some species that used to occur in natural reefs. Solid structures such as quay walls, pontoons, mooring posts and shipwrecks provide hard substrates to which oyster larvae can attach. Furthermore, harbours often provide a certain shelter, which facilitates larval settlement. In addition, the water quality has improved considerably in recent decades.

Offshore wind farms are a similar story. Underwater, the foundations transform into artificial reefs that attract life, from starfish and sea squirts to mussels and… Flat oysters. The structures are little disturbed because shipping and fishing are not allowed, while pilot projects focusing on the recovery of Flat oysters ensure more larvae in the water. That turns out to be exactly what a species like Ostrea edulis needs to regain a foothold.

A history of loss

The Flat oyster has a turbulent history in Belgium. It was once ubiquitous in the southern North Sea, and a culinary icon. Until the beginning of the 20th century, oysters were harvested in abundance from natural banks in the North Sea and watered down in so-called oyster pits on the coast, among others in Oostende (the famous Ostendaise). But due to overexploitation, habitat loss, pollution and the creep of diseases and the oyster parasite Bonamia ostreae, the species disappeared from our waters.

In the second half of the 20th century, commercial oyster farming switched to the Japanese oyster (Crassostrea gigas), which is easier to grow and less susceptible to the oyster parasite. As a result, Ostrea edulis also faded further into the background in Belgium.

Why is the return important?

Francis Kerckhof: “The rediscovery of the Flat oyster is not only culturally and historically interesting, it is above all an ecological story. After all, the Flat oyster is an essential part of the marine ecosystem. As a filter feeder, it helps keep the water clear, and its reefs create a habitat for countless other species. Where there are oysters, underwater life flourishes. Moreover, the Flat oyster is a native species, it belongs here by nature and its recovery can contribute to the marine recovery of the North Sea.”

In addition, this comeback is part of a broader European trend. In countries such as the United Kingdom, Germany, the Netherlands and France, reintroduction programs have been started to re-establish the species, and in Belgium there are also pilot projects supported by Belgian and European funding.

And now?

For scientists, this rediscovery is both an opportunity and a challenge. Can we use monitoring and DNA analysis to determine where these oysters come from? Do they come from isolated relict populations, did they come with shipping or ocean currents from locations where restoration projects are underway, or did the oyster larvae come from commercial oyster farming?

At the same time, the new knowledge also raises policy questions. Should we support this natural recolonization? Can ports or offshore installations be consciously designed as oyster-friendly structures? And how do we avoid repeating the same mistakes of the past, such as overexploitation or insufficient protection?

Thomas Kerkhove: “For the time being, the number of Flat oysters is still limited, and there is no talk of large populations yet. But the fact that Ostrea edulis is spontaneously appearing in various places is a hopeful sign. The sea shows us that, if we give it space, recovery is possible. In this context, every find on the beach or on a quay wall is a small reminder of the resilience of nature.”

Lhyfe Oostende BV  has submitted an application to obtain an environmental permit and a Natura 2000 permit for the construction, operation and dismantling of an offshore platform for the production of hydrogen, a pipeline to bring this hydrogen ashore and a high-voltage cable that transports electricity from land to the platform in the Belgian part of the North Sea. The offshore electrolyser platform is located approximately 1.2 km from the coastline and 600 m northeast of the eastern harbour dam of Ostend, within the circular safety zone around the Blue Accelerator. The platform will be installed approximately 190 m northeast of the Blue Accelerator. The planned coordinates of the platform are 51°14’57.3″N 2°55’22.4″E.

This application is subject to an environmental impact assessment procedure.

The Minister of the North Sea decides on this application by means of a ministerial decree.

The application and the environmental impact assessment report can be consulted at the offices of MUMM (Management Unit of the Mathematical Model of the North Sea) in Brussels (Institute of Natural Sciences, Vautierstraat 29, 1000 Brussels; mdevolder@naturalsciences.be; tel 02 627 43 52) or Ostend (3de en 23ste Linieregimentsplein, 8400 Ostend; jhaelters@naturalsciences.be; tel. 02 788 77 22), by appointment only and during office hours between 9:00 am and 5:00 pm. The application can also be consulted at every coastal community, during office hours.

The documents can also be consulted electronically:

• Application (in Dutch)
• Environmental impact assessment report (including concept of the appropriate assessment and non-technical summary – in Dutch)

Any interested party may submit its views, comments and objections to MUMM by letter or email until 13 June 2025:

MUMM
Attn. Patrick Roose
Vautierstraat 29
1000 Brussels

bmm@naturalsciences.be

Saltmarshes are among nature’s best defenses against rising sea levels, acting as natural barriers that protect coastlines. New research shows that dense vegetation on saltmarshes makes them more vulnerable to sea level rise because the vegetation hinders sediment transport. A surprising twist, as it was believed that dense vegetation played a crucial role in helping these ecosystems survive.

Using advanced computer modeling, the research team, led by Olivier Gourgue and Jean-Philippe Belliard from the University of Antwerp (Global Change Ecology Centre, department Ecosphere) and the Institute of Natural Sciences, examined how saltmarsh landscapes evolve over time. They discovered that while dense plants do trap sediment near tidal channels, they also block its movement toward the interior of the marsh. This means that instead of spreading evenly across the marshland, much of the sediment stays concentrated near the edges. Over time, this can lead to lower elevation levels in the marsh interior, making it harder for the ecosystem to keep up with rising sea levels.

These findings challenge the long-held assumption that denser vegetation always improves a marsh’s ability to survive environmental changes. By revealing how plant density affects sediment transport, the study, published in Limnology and Oceanography Letters, highlights the complexity of nature’s balancing act.

Saltmarshes and rising sea levels

A powerful numerical model called ‘Demeter’ was used to simulate 200 years of marsh development under different vegetation conditions. The model helped isolate the impact of plants on sediment movement, something difficult to observe in the field.

The computer predictions were later confirmed by real-world observations in China, where coastal areas with denser plant growth display the same uneven sediment patterns that increase vulnerability to rising seas. By combining their theoretical modelling with field observations published in Global Change Biology, Olivier Gourgue, Jean-Philippe Belliard and their collaborators provided a more complete picture of how marshes function over time.

Saltmarshes are critical for coastal protection, wildlife habitats and carbon storage. If they can’t maintain their elevation against rising seas, they may disappear. This would lead to increased coastal erosion, loss of biodiversity and reduced carbon sequestration.

Balancing sediment and vegetation

This research suggests that conservation efforts need to consider more than just planting more vegetation. It’s about understanding the entire sediment transport system and ensuring that marshes receive enough material to grow at a healthy pace. This carries important implications for policymakers and conservationists.

As Olivier Gourgue points out: “Coastal restoration projects often focus on planting more vegetation to stabilize wetlands. However, our findings suggest that encouraging a mix of plant densities or even allowing natural processes to determine vegetation growth may be more effective in the long run.”

Additionally, it’s crucial to ensure that sediment supply is maintained. Human activities such as damming rivers and dredging waterways can reduce the amount of sediment reaching saltmarshes, further endangering their survival and functioning as coastal protection. By understanding the delicate balance between vegetation and sediment movement, we can better protect these vital ecosystems and the benefits they provide for both nature and people.

The study that was published in Limnology and Oceanography Letters was the result of a collaboration between researchers affiliated to the ECOSPHERE Research Group of the University of Antwerp (Belgium), the Department of Earth and Environment of Boston University (USA), the Operational Directorate Natural Environment of the Institute of Natural Sciences (Belgium) and the Department of Physical Geography of Utrecht University (The Netherlands). For the Global Change Biology paper, the Belgian researchers collaborated with colleagues of the State Key Laboratory of Water Environment Simulation of Beijing Normal University, the Environmental Research Center of Duke Kunshan University and the State Key Laboratory of Estuarine and Coastal Research of East China Normal University (China).

A new European Marine Board Future Science Brief led by Professor Dr Sylvia Sander of GEOMAR Helmholtz Centre for Ocean Research Kiel warns that without better understanding of deep-sea ecosystems, sustainable management is impossible. The report, launched on 11 April 2025 via an online webinar, stresses the urgent need for targeted research and policy action to protect these critical but largely unexplored environments.

The deep sea, defined in this report as waters and seabed below 200 metres, makes up around 90% of the ocean’s volume. It plays a crucial role in biodiversity, climate regulation, and the global carbon cycle. Yet, this vast realm is increasingly threatened by oil extraction, fishing, mining, and climate change.

The European Marine Board’s Deep Sea and Ocean Health Working Group, comprising eleven researchers, presents ten key recommendations for sustainable governance and conservation. These include establishing an international scientific committee, improving environmental impact assessments, investing in long-term monitoring, enhancing education and technology transfer, and applying FAIR (Findable, Accessible, Interoperable, Reusable) data principles.

“The ocean is a connected system,” says Prof. Sander. “The deep sea cannot be managed separately from the rest of the marine environment.”

Historically considered inhospitable, the deep sea is now known to host complex ecosystems, including hydrothermal vents and abyssal plains. However, much remains unexplored. It’s estimated that 90% of deep-sea organisms are still undescribed, and key scientific gaps persist across physical oceanography, marine geochemistry, and ecosystem functioning.

Challenges in technology also hinder data collection. Current monitoring systems are often not suited for extreme depths, limiting our ability to track the impacts of activities like deep-sea mining. Understanding these systems is critical to ensure decisions are science-based and support long-term sustainability.

Human activities are already disrupting the deep sea, with warming, acidification, and oxygen loss accelerating due to climate change. Overexploitation of marine resources adds further stress. As the ocean regulates CO₂, produces over half of Earth’s oxygen, and supports life, its degradation poses global risks.

The authors see 2025 as a pivotal moment for ocean health. Achieving net-zero emissions by 2050 and curbing biodiversity loss now are essential to avoid irreversible impacts. “Climate change is one of the most alarming threats to life on Earth,” says Sander. “Combined with biodiversity loss, it could disrupt ocean systems permanently.”

Europe, the report suggests, has a unique opportunity to lead. Through strong international engagement and funding of transdisciplinary research, the EU can champion global deep-sea protection. This includes supporting underrepresented nations in research and recognising science as a human right.

Only through global collaboration and increased scientific investment can the deep sea, and the broader ocean, be preserved for future generations.

Download the publication here.

The Institute of Natural Sciences also focuses on research into the ecological structure and functioning of the deep sea. The assessment of the potential impact of human activities and the formulation of related policy advice are also given attention.

The Belgian Federal State is represented in the European Marine Board (EMB) by the Belgian Science Policy Office (BELSPO) and in the EMB Communication Panel by the Institute of Natural Sciences.

Early March, a passer-by found a dead dolphin washed ashore at the Scheldekaai in Burcht. The press attention for this exceptional find brought an even more remarkable fact to light: at the end of January, a ferryman had filmed a live dolphin further upstream in the Scheldt.

It was a strange surprise for Kobe Vercruyssen when he found a dead dolphin along the Scheldt in Burcht on 7 March 2025. The animal was lying about fifteen metres from the quay wall, and threatened to float back into the river with the rising tide. The news spread quickly via social media. Thanks to the quick response of Kobe and René Maes, who had rushed to the scene in the meantime, the carcass was tied to the quay wall with a rope so that it would not be lost.

After reporting to various authorities, the shelter ‘Wilde Dieren in Nood/Vogelopvangcentrum Brasschaat-Kapellen’ (VOC) eventually arrived on the scene to pick up the dolphin. The Antwerp fire brigade had to intervene to get the animal out of the water, after which the VOC brought the dolphin to the shed of the Agency for Nature and Forests (ANB) in Kalmthout for further examination.

Identification and cause of death

Analysis by ANB staff and the Mammal Working Group of Natuurpunt Antwerpen Noord & Kempen, in consultation with the Institute for Natural Sciences, determined that the animal was a young female with a length of 166 cm and an estimated weight of 70 to 80 kg. The skin was largely gone, making it difficult to determine what species it was. The teeth best match a common dolphin (Delphinus delphis), but a striped dolphin (Stenella coeruleoalba) could not be completely ruled out.

Because the carcass was already in an advanced state of decomposition, no exact cause of death could be determined. It was eventually taken away for destruction.

“The discovery and recovery of the Burcht dolphin was an example of rapid and efficient cooperation between citizens and various organisations, including Natuurpunt Waasland, Wilde Dieren in Nood/Vogelopvangcentrum Brasschaat-Kapellen, the Agency for Nature and Forests, the Institute of Natural Sciences and the Mammal Working Group of Natuurpunt Antwerpen Noord & Kempen. Despite the sad circumstances, this event offered a unique opportunity to study a rare marine mammal up close,” says Johan Neegers of the aforementioned mammal working group.

A surprising twist

The press attention that followed brought to light an even stranger fact, if possible. The discovery of the dead dolphin in Burcht reminded ferryman Nils Verbeeck of a special encounter that had happened to him more than a month earlier on the Scheldt, a long way upstream from Burcht. It prompted him to contact the Institute of Natural Sciences about it.

Nils appeared to have seen nothing less than a living dolphin in Hamme on January 31, 2025, and made a short movie of it that proved this beyond doubt. From the images it could be concluded that it was a common dolphin. It is very likely that this was the same animal that was found dead in Burcht 35 days later.

Common – and striped – dolphins are not adapted to life in rivers. They are species with a pelagic lifestyle, which means that they prefer the open sea and generally stay far away from coasts. Initially, it was suspected that the dead animal from Burcht had been drifted into the Scheldt by the tides, but this had to be adjusted based on the observation in Hamme. Why this dolphin swam so far up the Scheldt is not known. On the other hand, it is less surprising that she did not survive her visit to the river.

Rare appearance

Jan Haelters of the Institute of Natural Sciences explains how special the find is: “After the bottlenose dolphin and the white-beaked dolphin, the common dolphin is the most expected dolphin species in Belgian waters. Nevertheless, it remains a rare appearance here. In the past ten years, only a few cases of living common dolphins are known from our country, with an additional handful of observations where the identity could not be determined with certainty.”

Strandings of common dolphins are also rare in Belgium. On 22 December 2023, a recently deceased and therefore easily recognisable individual washed up in Ostend, but the other recent dolphins that possibly belonged to this species (one each in 2016, 2019 and 2020, and two more in 2023) were too decomposed to be assigned to this species with certainty. The common dolphin of Burcht and Hamme is not the first to be observed in the Scheldt, but as far as is known it is the one that swam the furthest up the river. In the Dutch part of the Scheldt, a common dolphin was observed near ‘s-Gravenpolder from the end of July to the beginning of September 2002. This animal was found dead in Saeftinghe on 8 April 2003.

The striped dolphin is even rarer in Belgian waters. This species has only been documented here with certainty twice: a stranding of a dead animal in 1981 and a sighting of a live animal from 15 to 19 May 2009. The latter also swam in the Scheldt (Doel and Verrebroek), did not survive this either and was found dead on 21 May of that year.

 

All persons and institutions involved are thanked for the smooth cooperation and flow of information. Forest rangers Bram Vereecken and Lucas Bergmans of the Agency for Nature and Forests respectively ensured the rapid internal reporting of the dolphin and the general coordination of the recovery and measurement of the carcass. Wilde Dieren in Nood/Vogelopvangcentrum Brasschaat-Kapellen ensured the transport to the ANB warehouse in Kalmthout.

Additional thanks go to Johan Neegers (Mammal Working Group Natuurpunt Antwerpen Noord & Kempen), René Maes (Natuurpunt Waasland), Jan Haelters (Institute of Natural Sciences) and Jaap van der Hiele (Stichting ReddingsTeam Zeediere, the Netherlands) for their cooperation on the text, and to Nils Verbeeck (Boottochten Jan Plezier), René Maes, Arlette Strubbe (Natuurpunt Waasland), Dafne Van Mieghem (Wilde Dieren in Nood/Vogelopvangcentrum Brasschaat-Kapellen) and Geert Steel (Mammal Working Group Natuurpunt Antwerpen Noord & Kempen) for providing the images.