Whales and phytoplankton, the real superheroes in the fight against climate change

Most people don’t think instantly about the ocean and its inhabitants when it comes to solutions to fight climate change. We hear about protecting the rainforest, flying less, renewable energy and eating plant-based. However, this is a missed opportunity, the oceans and marine life play a crucial role in capturing carbon from the atmosphere. One animal in particular has a leading role in this story — the whale.

The whale as 2-million-dollar investment

The International Monetary Fund (IMF) has estimated that one single great whale is worth more than $2 million. That’s a lot of money! Where is that figure coming from?

It’s a result of the role they play in the ocean’s ecosystem. The figure of two million dollars is partly based on their value for the tourism sector, but more importantly, because they help feed animals and plants across the oceans and therefore are essential for a healthy ocean. This is obviously a benefit for the fishing sector, but the most important reason a whale is worth that much is because of the carbon they help to take out of the atmosphere, together with their sidekicks, the phytoplankton.

Source: GRID-Arendal 2019, referenced by IMF

The whale as carbon sink

The whale captures carbon both directly and indirectly. Whales accumulate carbon in their bodies during their long lives. When they die, they take this with them to the bottom of the ocean, taking that carbon out of the atmosphere for centuries. According to the same IMF study, each great whale sequesters 33 tons of CO2, that’s equivalent to what 33 average trees absorb over their lifetime.

The even bigger impact, however, is coming from their support to the growth of phytoplankton. Phytoplankton, also called microalgae, are microscopic organisms that live in the water. They can be bacteria, but most are single-celled plants. Like other plants they use photosynthesis to transfer sunlight into energy, consume carbon dioxide and release oxygen. These microorganisms are the hidden side-kicks of the whale in this story. The IMF calculated that the current population of phytoplankton captures about 37 billion metric tons of CO2, an estimated 40 percent of all CO2 produced, equivalent to the amount of CO2 captured by four Amazon forests! If an increase in whale population would result in 1% increase of the phytoplankton population, the extra carbon they capture would be equivalent to the sudden appearance of 2 billion mature trees. So, it’s time for all the tree huggers to turn their eyes to the ocean.

The whale as fertiliser of the sea

This sounds impressive, but you are probably curious how this superhero team does their magic. Behind these incredible numbers is a story about poo.

In short, whales eat at the richer parts of the ocean and then bring those nutrients to parts of the ocean that are less abundant by relieving their waste there. Whales’ waste products contain exactly the nutrients, such as iron and nitrogen, that phytoplankton need to grow and allow them to thrive. With the whales’ ability to dive to the deep parts of the ocean, as well as, to travel long distances around the world, they feed where nutritious food is abundant and leave their pooh, full of nutrition, behind in the parts of the ocean where food is scarcer.

The vertical movement of the whales, by diving to the depths of the oceans and then coming up to the surface to breathe, is called the “whale pump”. Some whale species can easily go down to 2000 meters (2 kilometres!) below the surface where the water is black and freezing. As much fewer predators can access these parts of the ocean, food is generally widely available. After their lovely lunch or dinner, they come back up to the surface to breathe, and relieve themselves.The surface is where phytoplankton mostly hang out..

Photo by Richard Sagredo on Unsplash

The other big movement of whales is through their migration across oceans. This is called the “whale conveyor belt”. Humpback whales, for example, travel up to 5,000 kilometres from their feeding grounds in the cold waters of the Polar regions, to their breeding grounds in the warmer waters of tropical regions. They feed in the summer where food is widely available and during the winter they go to warmer places to breed and give birth, mostly fasting during this period.

Their ability to cover these vast distances across the width and depth of the ocean make these super spreaders of nutrition a key player to maintain the health of the ocean, which is essential to maintain and enhance the ocean’s capacity to capture carbon and mitigate climate change.

The whale as key player in the fight against climate change

Treehuggers and policy makers alike should look more often to the ocean when wondering what to do to make the world a better place. Don’t plant a tree but protect a whale. Join the effort to protect 30 percent of the oceans by 2030 (30×30). Support organisations like the World Cetacean Alliance that have made it their mission to save these majestic animals, that graciously keep this planet alive.