What 100 million year old creature brought on the ice age but is so tiny that a cluster can fit on your finger tip?
That would be Azolla!
This “super plant” is a genus of seven living species also known as Mosquito fern, duckweed fern, water fern, or my personal favorite, fairy moss.
This aquatic plant is called mosquito fern because of its role regulating mosquito populations, but that’s just one of its many functions that can benefit us humans, and ecosystem health in general. Azolla fix atmospheric nitrogen into helpful compounds, so they’ve been used as a natural, biological source of fertilizer, replacing intensive chemical fertilizers that can cause byproducts and consequences that are so destructive to ecosystems.
Most remarkably, its photosynthesizing impact can be so great that it is attributed as the key agent transforming one of Earth’s hottest, most greenhouse gas-concentrated periods into a planetary ice age. That is exactly the kind of global cooling superpower we need to understand and learn from now.
An amazingly productive plant
Azolla live in freshwater bodies like ponds, lakes, and the mouths of rivers, where they form a coating on the surface. Their overlapping, scale-like leaves enable them to float, while root tendrils hang down into the water.
These plants are full of reproductive power. Reproducing both sexually and asexually, they are able to double their biomass in as little as two days, given enough sunlight. However, this remarkable ability cannot be attributed to azolla alone. It turns out that these ferns have a symbiotic relationship with the blue-green algae Anabaena that is essential to their success.
The algae fixes atmospheric nitrogen that fertilizes the azolla so that its growth isn’t limited by the availability of nitrogen to its root system. In turn, azolla creates a microhabitat with favorable conditions for the algae to live. Because of their well-established partnership of nearly 100 million years, azolla and Anabaena have been called a “superorganism”.
A global climate changer
I became aware of azolla early in my Bio4Climate journey, as Jim Laurie introduced these amazing organisms to his Biodiversity and Symbiosis class, pointing to the amazing ability of living systems to create and change climate conditions.
I had come into class with a strong sense of fear, despair, and fatalism about our climate crisis, and very little understanding of the biological perspective on climate and Earth systems. At that point in my life and work, I had seen few truly encouraging “solutions” that could give me a sense of a future beyond my 20s. But Jim shared a few key insights and visions that opened my mind completely.
His Scenario 300 paper of a few years ago outlined a decade by decade roadmap of natural climate solutions that could actually address the crisis in my lifetime (!!) with ambitious but ultimately grounded actions. And in his slideshow presentation pulling together molecular chemistry, geologic history, personal stories from restoration work, and everything in between, Jim took us on a visit to an earlier instance of intense temperature and greenhouse gas effect in the Earth’s history.
We learned about the Paleocene-Eocene Thermal Maximum (PETM) and some hypotheses around how Earth cooled off from that high point, going from a state in which rainforests covered the globe, including Arctic regions, to a point where polar ice caps formed and the cooling snowballed all the way into an ice age. One theory is called the Azolla Event, which describes a scenario in which azolla formed in the mouths of rivers depositing into the Arctic Ocean and on layers of freshwater that extended out into the ocean. These large mats of biomass absorbed CO2 via photosynthesis, but died off under cooler temperatures and sank to the ocean floor, carrying large amounts of carbon with it.
This in turn furthered cooling in a positive feedback loop that, along with other biogeological conditions, allowed the Earth to cool substantially. You can read more on the Azolla event and some of the research behind the theory here.
Now, as we face our own runaway global warming, researchers and restorers are exploring ways to harness the photosynthesizing capability of azolla and other plants to convert carbon into biomass and rebalance our carbon cycle. And azolla can do much more than grow quickly and sink to the ocean floor! It can be used as food, fodder, biofuel, and fertilizer, and the more we are open to these possibilities, the more we can discover about how to replace our extractive systems and behaviors with renewable alternatives like those offered by living organisms.
A unique ally
These days, people have found numerous uses and functions endearing azolla to them. As mats of azolla spread out across a water body’s surface, they keep adult mosquitoes from laying eggs and prevent larvae from being able to emerge and develop. This natural mosquito control can reduce breeding populations by 95%, in a major win against the illnesses (and annoyance) they carry.
As it metabolizes nitrates and phosphates and removes them from the water bodies it inhabits, azolla also discourages massive algal blooms. These algal blooms can limit sunlight below the surface and oxygen availability, disrupting food webs, creating dead zones, and throwing ecosystems off-balance. Furthermore, as azolla is used as a natural fertilizer, it can displace the chemically intensive fertilizers whose runoff contributes to the concentration of nitrates and phosphates and sets off these destructive ecological domino effects.
Indeed, many people rely on azolla as a steady supply of bio-fertilizer, because the nitrogen-rich fern (thanks to its endosymbiont Anabaena) can provide this essential molecule to cultivated crops. Farmers have been using it in rice paddies across Asia for this purpose. It is also used as animal feed, with a high protein content comparable to soybean.
Enterprising humans have begun exploring how to cook and consume azolla and introduce it into our diets. The Swedish artist and researcher Erik Sjödin delved into the possibilities in his book, The Azolla Cooking and Cultivation Project, where he detailed his efforts to cultivate and eat azolla, using it as the main ingredient in recipes for azolla pancakes, azolla burgers, azolla soup, azolla bread, and more. If you are what you eat, maybe we can be superorganisms too!
Take a look at some of the uses and promise of Azolla:
Though there are no silver bullet solutions to climate change, there are many promising interventions we can make, and countless opportunities to be creative, adaptive, and better integrated with other living creatures and the ecosystems around us. To me, azolla represents that hope for a truly symbiotic relationship. It teaches me that great change is possible, and that enables me to keep on going and working toward balance and abundance for this planet I call home.
In the spirit of growth,
Maya Dutta is an environmental advocate and ecosystem restorer working to spread understanding on the key role of biodiversity in shaping the climate and the water, carbon, nutrient and energy cycles we rely on. She is passionate about climate change adaptation and mitigation and the ways that community-led ecosystem restoration can fight global climate change while improving the livelihood and equity of human communities. Having grown up in New York City and lived in cities all her life, Maya is interested in creating more natural infrastructure, biodiversity, and access to nature and ecological connection in urban areas.
How Azolla Changed the Earth: https://www.youtube.com/watch?v=gdfWFDcXut4
Hank Green video on the PETM: (azolla makes an appearance at 8 minutes): https://www.youtube.com/watch?v=ldLBoErAhz4