Ecomare

During warm, peaceful summery days, it's hard to imagine that the Wadden Sea can also turn into a rough and dangerous sea. The strong currents ensure that no two days are the same in this tidal region. One of the characteristics of the wadden region are all the creeks and channels: the smaller and larger streams of water separating the mud-flats from one another. During flood, the seawater first flows through the various streams, eventually flooding the flats. During ebb, the water retreats along the many creeks back into the major channels.
These creeks and channels are constantly changing due to the force of the sea currents. In just one year, they can shift to other positions or even entirely disappear!

The tidal flats can also shift around, depending on the sea currents. Tidal flats consist of sand or mud. The size of the particles and the motion of the water determines when the sediment settles to the bottom. Larger, heavier sand particles settle where water has slowed down but can still be moving. These sandbanks are found near beaches of around tidal inlets. The very fine mud particles will only settle to the bottom when there is no motion, such as at high tide.

As bare as they may appear, the tidal flats are teeming with life. Besides the brown-goldish layer of plankton on the surface, thousands and thousands of worms, shellfish and other animals have made their home in this sandy or muddy environment. And some flats are practically covered with shellfish or eelgrass. All this hidden life is the reason why so many birds come to the Wadden Sea to forage during migration.

The Wadden Sea is constantly changing and that is due to the tides. At one moment, you see only water, while several hours later you see immense tidal flats. It is possible to hike these tidal flats, although you must be very careful. They can be very treacherous! The Wadden Sea owes its name to the fact that it is wadable. Although nowadays we hike the flats for fun, it used to be a way of life in some parts of the wadden region.

The tide is one of the most influential aspects of the Wadden Sea. It is responsible for the rise and fall of the seawater. Thanks to the tide, we have high and low tide in the wadden region twice a day. In between, there is ebb and flood.

The rise and fall of the seawater causes currents. The greater the difference between high and low tide, the stronger the current. In the Netherlands, the difference between high and low tide is less than in Germany and Denmark. That means that the Dutch islands have much fewer problems from strong currents. You can see this effect by the size of the indiviudual Wadden Islands. The German and Danish islands are much smaller than the Dutch. You can also see the strength of the tides by the sea inlets between the islands. The greater the difference between high and low tide, the greater the amount of water that needs to pass through the inlet and the wider it gets. The sea inlets in the Netherlands are much narrower than in Germany and Denmark.

A strange phenomenon we see in tidal regions such as the Wadden Sea is the slack water areas. These are the places where sea currents collide behind an island or sandbank. The currents lose all their strength and the water seems to be stagnant. Very fine material which has been carried by the sea, such as mud, now has the chance to sink to the bottom. In that way, new pieces of land can form. One example is the tidal flats by the Schorren on Texel.

Slack water areas are the most shallow parts of the Wadden Sea, where ships with little draught are just able to cruise during high tide. During low tide, these areas are where tidal flat hikers cross from one mud-flat to the next.

Not only is the tide responsible for how the wadden region looks. That rise and fall of the sea is also very important for the plants and animals that live here. Every time it's flood, the Wadden Sea receives a new supply of nutrients. This food forms the basis for a complicated food web. The very tiny plants, larva and small animals survive on this food, and in turn they are eaten by slightly larger animals, which are consumed by even larger animals. (Of course, you get lots of exceptions, such as large whales eating small krill.) Without the supply of nutrients two times a day, there would not be much life found here. Therefore, the tide is of vital importance for the wadden region and the Wadden Sea.

Unfortunately, the tide doesn't only bring good things to the wadden region. In addition to nutrients, all kinds of materials are also carried into the region, such as pesticides, oil and marine litter. Sometimes, they are toxic. Other times, they are devious killers, that choke birds or seals to death. Every once in awhile, a poisonous material suddenly appears in the area in large amounts. That usually means there has been an accident with a ship somewhere nearby, where containers with toxic material have fallen overboard. For example in 1994, thousands of bags with agricultural poison fell overboard. Luckily, only a few of these bags reached the Wadden Sea.

The Wadden Sea is a nutrient-rich area thanks to the influence of the tide. Nutrient-rich areas are usually also rich in plants and animals. However in the Wadden Sea, there are not all that many different species of plants and animals. The tide is also partially responsible. Ebb and flood are are the reason that the Wadden Sea totally changes in appearance twice a day. Every few hours, the mud-flats are either exposed or flooded. Species that live here have to deal with these extreme circumstances. The water disappears, the temperature changes and the oxygen and salt levels are constantly varying. As plant or animal, you have to be able to withstand all these things!

Nevertheless, you do find a lot of plants and animals in and around the Wadden Sea, even though the amount of species is limited. The most well known animals are the seals, of course. They don't just use the Wadden Sea to look for food; they also use it as a nursery. Many young seals are born on the sandbanks in the Wadden Sea. There are also a lot of fish from the North Sea that migrate to the Wadden Sea after birth, for example, sole and plaice.

It is a busy place on and around the tidal banks that lay exposed during ebb, whether or not they are made up of shells, mud or sand. They are not called the coral reefs of the Wadden Sea for nothing! Lots of plants and animals are found here, such as plankton, worms, shrimp, crabs and fish. Many of the birds are dependant upon these large amounts. More than 12 million of these feathery friends make use of the Wadden Sea. Tens of thousands of them are migrating birds. Twice a year, they forage for food in the muddy tidal flats in order to gain sufficient strength for a long journey.

Should the Wadden Sea run into problems, than the birds also run into problems. Momentarily, the amount of shellfish in the Wadden Sea is declining. That has consequences for shellfish-consuming birds, such as knots and eiders. 

Unfortunately, the number of plant and animal species is not just increasing. Some species are also (almost) disappearing. For example, eelgrass. You used to find large fields of this saltwater plant in the Dutch Wadden Sea. Nowadays, there are only a few places where it can be found.

A number of plant and animal species now found in the Wadden Sea are having problems. They threaten to disappear from the region for various reasons. Overfishing and climate change are some of the reasons. Flounder, plaice, eel and whiting have been declining greatly, as well as the number of mussel and oyster banks.

In June 2009, the Dutch and German parts of the Wadden Sea, with the exception of the federal state of Hamburg, were added to Unesco World Heritage List. This underlines the fact that the area has such major nature value for the world that it deserves special protection. Nature and environmental organizations, as well as entrepreneurs in and around the Wadden Sea, are very pleased with this nomination. The new status means recognition of this exceptional region and a prognosis for a higher influx of tourists, which helps to strengthen the economy. The areas on the landside of the dikes on the inhabited Wadden Islands are excluded from the World Heritage status.

The fishery sector is less enthusiastic about the nomination. They recognize the Wadden Sea's exceptional value but are still concerned. They fear that the nature and environmental organizations will seize the new status to object to fishery activities in the Wadden Sea. Even when the regional governments in the wadden region and the Minister for fisheries agreed to no limiting factors for the fisheries in the area, they are still distrustful.

The fact that the Danish part of the Wadden Sea is not yet on the list is because they withdrew from the preparations for nomination. At that time, Denmark was in the process of establishing the Wadden Sea as a National Park. In October 2010, the Wadden Sea between the German island of Sylt and the Danish bay Ho-Bugt received the National Park status, opening the doors for a nomination for the World Heritage List. It is expected that the Hamburg Wadden Sea National Park will be nominated and later added to the list in 2011.