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Credit: James Watt/NOAA


Artificial Reef Made From Pear Trees Proves Effective In Netherlands Test

A pyramid of pear trees in the Wadden Sea is proving to be a successful way to make an artificial reef that can support marine life.

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Most people think of a reef as a place where scuba divers go to gaze at exotic fish, but it is more than that — much more. A reef is to the ocean what a forest is to dry land. It is a place of refuge from predators, a spawning ground, and a way to protect coastlines from powerful storms. Scientists say that 25% of all marine life begins in the world’s reefs.

According to Wikipedia, most reefs are an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs were formed after the last glacial period when melting ice caused sea level to rise and flood continental shelves, and are less than 10,000 years old. As communities established themselves, the reefs grew upwards, pacing rising sea levels. Reefs that rose too slowly died because they were too far below the surface to receive enough sunlight to survive.

Coral reefs have declined by 50% since 1950, partly because they are sensitive to water conditions. They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification, overfishing, and harmful land use practices, including runoff and seepage from injection wells and cesspools.

The Essential Reef

A reef is like a canary in a coal mine. It can give advanced warning of changes in the environment that will affect all life on Earth, including humans. Coral cannot relocate if the water they live in gets too hot. Instead, they die. The calcium carbonate structure they create can dissolve if the water gets too acidic, which is what is happening now as more and more carbon dioxide gets absorbed by the oceans.

People have been trying any number of ways to create artificial reefs to replace the ones that are dying. Old ships are decommissioned and sunk offshore to provide a habitat for marine life. Others are electing to have their ashes mixed with cement and dropped into the ocean after they are cremated.

Researchers in the Netherlands have a different approach. They are creating pyramid-shaped structures from pear trees and dropping them into the Wadden Sea along that county’s northern coast. Jon Dickson, a Ph.D candidate at the Royal Netherlands Institute for Sea Research, told The Guardian, “We have fossil records of sunken wood communities dating back to the Jurassic period. We are trying to simulate what it used to be like. [Because] trees are cheap and waste products, it’s cheaper to scale than using concrete or sunken ships.”

Those wooden structures have been in the water for more than six months and the results are encouraging. They are now home to algae and more than 15 species that are immobile and typically anchored to a surface, like barnacles on the hull of a ship. They also are home to three times more species of fish than control areas without the artificial wooden pyramids.

A reef is where fish go to spawn. The structure of the reef provides protection from predators for the hatchlings. Scientists estimate more than a million species of marine live are at risk of extinction if the world’s reef system is compromised. “Hopefully we can push the knowledge that we’ve learned into other similar systems, [such as] in the North Sea and help the fish population recover there,” Dickson said.

He added, “I’d love to do [this experiment] somewhere with clearer water where we can actually visually observe how these reefs are providing habitat for fish and other organisms, as well as elsewhere in the Netherlands and North Sea. The flora and fauna vary even 200 km down the coast, so I’d be fascinated to learn. You also have different [types of] trees in different places. So is that affecting what’s going on there?”

“I’m really hopeful that we can kickstart the formation of natural reefs again by creating biodegradable reefs. [In] the southern North Sea there used to be 30% oyster reefs, now it’s less than 1%,” he said. I feel like we’re at the point in this global biodiversity crisis where we need to accept that we don’t know all the answers and just start doing it on a wide scale [because] some action is better than no action.”

In 2017, researchers in Germany published similar findings after studying deep sea organisms that inhabited sunken tree logs. They found that different species were attracted to the sunken wood depending on the location.

Artificial Reef Technology Expands

We know more about the back side of the moon than we do about the oceans here on Earth, which cover about two-thirds of the planet. For centuries, coastal people have relied on the oceans for food, little realizing the role a reef can play in nurturing young fish early in their lives. The demise of the world’s reef population is a phenomenon that scientists have been aware of since the 1950s.

In other words, the signs of the deterioration of the natural environment has been known for a long time, but little has been done about it because the causes of a deteriorating environment have been unclear, and what little was known was often covered up by those who wanted to protect their own selfish economic interests.

Now, with nearly half of all reefs in the world dead or dying, researchers are busy experimenting with ways to devise an artificial reef structure that will replace the one nature created. That is laudable. Change is inevitable and adaptation is an essential part of life. But perhaps we need to look a little deeper into the problem to identify why a reef dies and what we can do about it.

The one thing people will never be able to do is claim there was no way to know about the destruction of the environment caused by human activity. The signs are all around us in the form of hotter, drier weather, rampaging forest fires, melting glaciers, and more destructive storms.

Constructing an artificial reef is a worthy endeavor, but hardly sufficient to address the calamity of an overheating planet. It took 10,000 years for the Earth’s reef infrastructure to form. It may take another 10,000 years to fully undo the damage caused by human habitation.

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Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."


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