Oceans as a Life Source

Did you know that the oceans cover 71% of our planet’s surface? That makes them the largest ecosystem in the world. They are also a life-support for the Earth and are critical to human survival. Oceans provide things that humans depend on, such as food and energy, and they are home to millions (if not billions) of sea creatures. Oceans also help regulate Earth’s climate. They absorb excess heat from the atmosphere, and they influence when and where it rains. The famous marine conservationist Dr Sylvia Earle once said: “If you think the ocean isn’t important, imagine Earth without it. Mars comes to mind. No ocean, no life support system”.

Blue Carbon Ecosystems

Coastal habitats, like mangrove forests, seagrasses, and tidal marshes, are three marine ecosystems that play a big role in regulating Earth’s climate (Figure 1) [1]. Seagrasses are underwater flowering plants, like the grass you see on land, but living in the sea. Mangrove forests are made up of trees with clusters of tangled roots that grow in saltwater, and tidal marshes are made up of plants like herbs, grasses, and shrubs, growing on land where the tides flow in and out. Scientists have found that these ecosystems, sometimes called blue carbon ecosystems (“blue” as they are near the oceans, which look blue) are very good at capturing carbon dioxide (CO₂) from the atmosphere and trapping it. This is important because when CO₂ builds up in Earth’s atmosphere it can trap heat from the sun and cause weird and dangerous weather, similar to what people all around the world have been witnessing in recent years.

How do blue carbon ecosystems capture and store CO₂? Think back to your lessons on photosynthesis and how trees and other plants capture and store carbon. Just like plants on land, mangroves, seagrasses, and marsh plants capture CO₂ from the atmosphere and store it in their leaves and roots. But blue carbon ecosystems have a secret weapon for storing carbon longer than most plants on land can—they bury it in the ground and trap it there for thousands of years. This is because their roots are in wet, muddy soil, where there is very little oxygen and decomposition is very slow. This long-term carbon storage is important for keeping CO₂ out of the atmosphere and reducing climate change (Figure 2).

Beyond Climate Change

Blue carbon ecosystems offer more than just their remarkable carbon capture and storage functions. Blue carbon ecosystems provide valuable services to humans and the environment (Figure 3). They act as natural shields that protect coastlines and coastal cities from the fury of big waves and storms, and they help clean pollutants from the water. These special ecosystems are also home to many marine animals, including animals that people like to catch and eat, such as fish and crabs. They are also nature’s storehouses, supplying communities with important resources including wood, medicine, and recreational opportunities. Who does not enjoy a day outdoors marveling at all the birds, fish, interesting plants, and other incredible creatures that call blue carbon ecosystems home?

The Big Questions

Our team of scientists has been studying blue carbon ecosystems for over a decade. We have been trying to answer some big, important questions about how tidal marshes, mangrove forests, and seagrasses help control Earth’s climate [2]. One of our first discoveries was that good information on exactly where these ecosystems are found or how they have changed over time did not exist. We needed to find out this important information because it tells us how many of these valuable blue carbon ecosystems have disappeared (Spoiler alert: more than 50% of our blue carbon ecosystems have already vanished [3]). We also needed to know how much carbon is being trapped by blue carbon ecosystems, and what happens to all the carbon trapped in the ground when these ecosystems are destroyed. After all, if that carbon gets released back into the atmosphere as CO₂, it will make climate change worse—yikes! Finally, we wanted to know whether bringing back the blue carbon ecosystems we have lost, a process called restoration, can help us battle climate change in a big way.

In general, we can combine all of our research questions into one big question: What can we achieve if we use blue carbon as a natural solution to Earth’s changing climate [4]?

What We Discovered

Through our research, we made a number of fascinating discoveries about blue carbon ecosystems. First, we found that when we add up all of Earth’s blue carbon ecosystems, they cover an area that is somewhere between 0.36 million km² (about the size of Japan) and 1.85 million km² (about the size of Mexico). That is a super wide range, and it illustrates just how uncertain we are about how much of Earth’s surface is made up of blue carbon ecosystems. The biggest problem is that we do not have good tools for finding seagrass ecosystems. We can use satellites to search for mangrove forests and tidal marshes from space, because their plants mostly grow above the water’s surface, making them easy for satellites to spot. However, seagrasses grow beneath the water, where satellites cannot see them so well.

Using our estimates of the size of blue carbon ecosystems, as well as other data like the amount and condition of plants and soil in them, we can use advanced calculations to estimate how much blue carbon exists on Earth. We found that the total amount of carbon stored in mangroves, seagrasses, and tidal marshes ranges from 10–30 billion tons. That is a really large number! To put it into perspective, an adult blue whale weighs about 140 tons. That means all the Earth’s blue carbon ecosystems together are storing the equivalent weight of more than 100 million blue whales!

Finally, we found that protecting the blue carbon ecosystems that remain and restoring the ones that have been lost are powerful tools in the fight against climate change. By protecting current blue carbon ecosystems from human-caused destruction, we can prevent 300 million tons of CO₂ from escaping to the atmosphere each year. To put that in perspective, that is the same amount of CO₂ emitted into the atmosphere yearly by the country of Australia. Additionally, if we restore the blue carbon ecosystems that have been lost, we can trap an additional 840 million tons of CO₂ each year. If we take care of the blue carbon ecosystems that remain and work on restoring the ones that have been lost, it could balance out 3% of the greenhouse gases we put into the atmosphere! And do not forget that when blue carbon ecosystems trap carbon, it remains buried in those systems for thousands of years!

Taking Action Together

In conclusion, this article reveals the hidden heroes of our planet: blue carbon ecosystems. These incredible marine ecosystems play a vital role in fighting climate change by capturing CO₂ and keeping it safely stored underground for thousands of years. By protecting and restoring blue carbon ecosystems, communities can make a significant contribution to reducing climate change, safeguarding coastlines, and preserving the homes of millions of sea creatures. So, what can young people do to help blue carbon ecosystems thrive? Learning about these incredible environments and spreading awareness about their importance is a significant step—you can help others to understand how critical these ecosystems are to our planet! Supporting conservation activities and being mindful of actions that might harm blue carbon ecosystems can also make a real impact. As future stewards of Earth, you hold the key to ensuring the health and survival of blue carbon ecosystems and, therefore, a healthier and safer planet for all living beings. Let us embark on this journey together and celebrate the wonders of nature’s natural climate solutions!

Glossary

Blue Carbon: ↑ Carbon that is captured and stored by coasts and oceans; in particular, by coastal vegetation such as seagrasses, mangroves, and tidal marshes.

Ecosystem: ↑ An area where organisms (like animals, plants, bugs) interact with the physical environment (like water, dirt, rocks, nutrients, and sunlight).

Restoration: ↑ Actions taken to repair natural ecosystems that have suffered from human or natural impacts. For example, replanting mangrove trees after they were chopped down for firewood.

Greenhouse Gas (GHG): ↑ Gases in Earth’s atmosphere that trap heat from the sun. The most concerning greenhouse gases produced by humans are the ones causing global warming, which include carbon dioxide and methane.

Acknowledgments

We are thankful for the funding provided by Deakin University (to PM and MC) and an Australian Research Council Discovery Grant (to PM and CD; DP200100575).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.