River biodiversity loss is enormous and is in urgent need of restoration. Freshwaters, like rivers and streams, cover less than 1% of all the water on the earth but still provide a habitat for 40% of all the world’s species. This wildlife needs to be protected. Since the 1970s, the global freshwater species have declined by 84%, primarily due to human interference, such as encasing rivers in concrete. The ecosystem is under pressure. Streams are becoming unhealthy.

Healthy streams are not straight. They have an organic structure, grown naturally over decades. The water can run free at a good pace. A high flow rate leads to soil loss, erosion, and habitat degradation.
Rivers need texture, nooks, and crannies for wildlife to thrive and to create a balance. An equal amount of sediment is coming in vs. going out. The water should not run too slowly or too fast to form a healthy river and improve biodiversity.

Sources: Natural Stream Restoration (see also Part II and III), River Restoration, Rivers are key to restoring the world’s biodiversity, Standford, Extinction of freshwater species, Hindustan Times.

What if we could design an efficient way to restore rivers in symbiosis with nature?

One traditional way to solve the problem is the faggoting technique with faggot bundles. They are used in rivers and streams to stabilize the bank side erosion and to narrow a stream when it has been over-widened over the years. Faggot bundles or fascines are usually made of wood sticks bundled together with a strong rope.

In an ideal world, all wood materials should be free of splits, rot, disease, and insect infestation. The bundles are made of wood sticks since they must be made in a natural/biodegradable material that offers nooks and crannies for freshwater wildlife to hide and thrive in. As the bundles biodegrade, they will become part of the riverbank over time, narrowing the stream as it feeds the food chain.

The faggot bundles also hold plants or seeds that will sprout, to stabilize the riverbank in the long term. Plants that thrive with lots of water and long root systems are best for better stabilization. The vegetation roots will, over time, act like a rebar, binding soil to resist erosion. The growing vegetation also provides the water with oxygen and cools down the streams and rivers, enhancing freshwater biodiversity.

Sources: Live and inert fascine streambank erosion control, How to stabilize your shoreline with live fascines, River restoration on the River Eye

The traditional practice of faggot bundles is, unfortunately, flawed. The fascines are built by hand and placed manually. Today it seems inefficient and very time-consuming. In recent years, NGOs and volunteers have kept up with the initiated projects.
The amount of wood/forestry is immense to save relatively small areas. Therefore, the practice is appropriate for areas where wood is limited.
And lastly, the ropes are seldom biodegradable. Usually, synthetic yarns are used since they are more robust and last longer. This leads to another issue: The strings break down and create microplastics that end up in the rivers and later in the oceans, ruining biodiversity in other places.

Sources: Effect of Deforestation, Saving trees or improving lives

Mushroom mesh to the rescue

To solve the problem, I thought about molding a biodegradable (nature-friendly) structure based on mycelium. If the river or stream is shallow, roughly 1x1m can be adapted with smaller molds. Mycelium is very strong and lightweight—like wood—yet available at scale. It can be molded in a vacuum-formed rPET frame for efficient and cheap production. Multiple structures can be developed at the same time. Not all have to be done by hand.
Mycelium is very resource friendly. No wood must be chopped down. No synthetic rope that adds microplastics for attachment.

I imagine a starter kit consisting of 2 parts:

  • The Mycelium Starter.
    Mycelium (given a fungus culture) can grow within any local bio-waste. The only thing you must remember is that the difference in bio-waste affects the density of the finished structures, e.g., woodchips make Styrofoam-like density, and straw makes wood-like density.
  • The Plastic Mold.
    Vacuum-formed it’s an easy, simple, quick, and cheap method to form the mycelium structure. I prefer an rPET plastic mold as it is affordable, strong, long-lasting, versatile, more sustainable, and can be recycled many times at the end of life (EOL).

It would be best if you had some basic stuff. The culture to start your mycelium can be shipped anywhere in an envelope. You can use any agricultural or bio waste bound (e.g., from hemp, wood chips, psyllium husks, straw). If available, go for straw which is less resource-heavy. Straw also makes it less water resistant, which is preferred since it should biodegrade in the water over time. The growth period is 2-7 days, depending on temperature and moisture ratio.
An oven is sufficient to burn the structure after molding and stop the growth. It only needs 200°F or 95°C to stabilize the structure.
After stabilization, add soil from the river zone and local seeds or (water) plants. Place one line of mycelium brigs in a shallow river or build a structure for streams at the riverbank sides. Wait for nature to do its job.

See also: PET vs. PVC, Made of mushrooms, Vacuum Forming, Mycelium-based Composites.

The benefits of this approach

The molded mycelium structure works similarly to the common faggoting technique. It will strengthen weak riverbank sides. It will give the river structure to moderate the water flow pace and stop erosion.
The nooks and crannies will enable wildlife to live and thrive for improved biodiversity. The integrated seeds will provide water plants and trees that will slowly naturally replace the structure as it biodegrades. Like the faggoting technique, the vegetation roots will grow like a rebar, binding soil to resist erosion.
As the brigs are stackable, you’ll need no plastic wires or additional tooling.

The solution suits any place with erosion problems or needs more stream and river biodiversity. You could think about the following:

  • In the city where concrete covers the riverbanks
  • Rural areas where over-widened rivers provoke weak riverbanks.
  • Places where deforestation is an issue.

In the long run, it is a way more sustainable process than, for example, using wooden bundles. It takes about 50 years to grow a tree, and the mycelium only takes 2-7 days and can be redone repeatedly, not using nature faster than it can regrow or regenerate.

In addition, I integrated the area for the plants that are very much needed to avoid the extra step required for the traditional approach.

See also: Plastic gets to the ocean, Microplastic in the Ocean, Microplastic.

You could even think of using the brigs as a living sea wall. Volvo did something similar, but 3D printed, so way more expensive and less nature friendly.
Let me know what you think about the faggot technique, my approach, or river protection in general. I am curious!

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