Once the giants of the ocean, whales are now struggling to survive against an onslaught of human-driven threats. 

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Whales play a vital role in combating climate change by driving nutrient cycling, fertilizing carbon-absorbing phytoplankton, and serving as carbon stores through their bodies. Their movements enhance marine ecosystem productivity and support global climate stability, making their conservation essential for a sustainable future. Yet, anthropogenic threats continue to endanger these magnificent mammals, highlighting the urgent need for stronger protection and restoration measures.

When it comes to tackling climate change, one of the most promising solutions may lie in the flippers of the world’s largest creatures: whales. 

Their ecological role in ocean ecosystems extends far beyond their majestic size, as they help regulate the global climate. This is possible thanks to their critical contribution to nutrient cycling and ocean mixing, which promotes phytoplankton growth. Phytoplankton, which are responsible for the majority of photosynthesis on Earth, sequester carbon and play a vital role in regulating the climate. 

So, protecting whales is not just about preserving biodiversity; it is a crucial step in combating climate change. 

Human activities continue to endanger whale populations, and current restoration efforts remain insufficient. As the climate crisis intensifies, restoring whale populations becomes an increasingly powerful tool for climate mitigation and marine ecosystem preservation. This restoration represents an effective nature-based solution, a term referring to the use of natural processes of healthy ecosystems to protect communities, enhance infrastructure, and ensure a sustainable and diverse future.

How Do Whales Stimulate the Growth of Phytoplankton? 

The answer lies in their feeding behaviour and movement within the ocean.

Whales dive deep into the ocean to feed on nutrient-rich prey such as squid, fish, and krill. After feeding, they return to the surface to breathe and sometimes to breed. As they do, they release nutrients ingested from their prey in the form of faecal plumes, creating a nutrient-rich layer at the ocean’s surface. 

These plumes contain essential nutrients, such as iron and phosphorus, that fertilise phytoplankton, creating ideal growth conditions. This stimulates rapid phytoplankton growth, leading to what is known as a phytoplankton bloom. 

Additionally, whales promote marine ecosystem health through their vertical movements between ocean layers. This process brings nutrient-rich waters from the deep sea to the surface, enhancing conditions for phytoplankton growth and productivity. 

Small but mighty, phytoplankton are the unsung heroes of Earth’s carbon cycle. These tiny photosynthetic organisms absorb around 40% of the carbon fixed each year globally and produce nearly half of the world’s oxygen, making them essential to global carbon sequestration. When phytoplankton die and sink to the ocean floor, they sequester carbon in deep ocean sediment. Ultimately, phytoplankton are essential for carbon sequestration and long-term storage, playing a critical role in regulating the global climate. As whales positively impact phytoplankton growth, their conservation is directly tied to maintaining climate stability.

Not only do whales help sustain ocean productivity, their large biomass means their bodies play a significant role in carbon storage.

Over their lifetimes they store an average of 33 tons of carbon, far more than the 12 tons stored by an oak tree. This is due to their large size and long lifespans. As apex predators, whales store carbon by consuming prey from lower trophic levels that are rich in carbon. When they die, their bodies sink to the seafloor, where the carbon is stored for centuries or even millennia. As the whale carcass decomposes, some of the carbon becomes integrated into ocean sediments, effectively sequestering it. Additionally, deep-sea organisms feed on the carcass, recycling part of the carbon through the ecosystem instead of releasing it back into the atmosphere as carbon dioxide. 

Under Threat

Once the giants of the ocean, whales are now struggling to survive against an onslaught of human-driven threats. 

Despite their vital role in climate mitigation and ecosystem health, whales face unprecedented challenges that jeopardize their health and survival, from plastic ingestion to noise pollution, climate change, and whaling. Whales often ingest plastic, leading to digestive blockages, exposure to toxic chemicals, and other serious health problems. Additionally, when smaller marine organisms consume plastic, toxins accumulate up the food chain and affect whales in concentrated amounts. 

Whales rely on their auditory systems for navigation, communication, foraging, and breeding. As a result, anthropogenic noise pollution, such as that from shipping, sonar, and seismic testing, poses a significant threat with the potential to kill whales. Noise pollution has been shown to disrupt whale communication, migration, and breeding behaviours, while also causing long-term stress. In some cases, it can lead to brain haemorrhages and has been linked to whale strandings. Rapid climate change further challenges their survival by altering migration routes, degrading habitats, and increasing disease risks. 

Despite the International Whaling Commission’s 1986 ban on commercial whaling, countries like Japan, Norway, and Iceland have continued to kill over 40,000 whales, undermining recovery efforts. Given these escalating threats, urgent action is needed to mitigate these risks and strengthen protection efforts to help whale populations thrive.

The decline in whale populations is creating ripple effects throughout marine ecosystems and accelerating climate change. With fewer whales, nutrient cycling diminishes, leading to reduced phytoplankton growth. Phytoplankton, crucial for carbon sequestration and a primary food source for many marine species, are essential to both oceanic food webs and climate regulation. 

As British broadcaster and biologist David Attenborough noted, “To restore stability to our planet we must restore biodiversity. The very thing we’ve removed. It’s the only way out of this crisis we’ve created. We must rewild the world.”

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