What’s small, pink, and can be seen from space? The answer depends on your perspective.

To the whales, seals and penguins of the Antarctic: it’s dinner. To you and me: it’s a small creature called krill, which forms the bedrock of the Antarctic food web. But unfortunately, and as a new report by Greenpeace lays bare, for an expanding multimillion dollar fishing industry: it’s an investment opportunity.

One of the quirks of life on our planet is that the biggest creatures to have ever lived, blue whales, depend on something no bigger than your little finger: krill. Gathering in their billions, these tiny crustaceans form vast clouds of pink in Antarctic waters which can stretch for miles and show up in satellite imagery.

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Blue, humpback, fin and minke whales all consume krill – some up to two tonnes in a single day. Penguin colonies across the Antarctic are strewn with pink-stained snow because of the volume of krill they eat. Fur seals, crabeater seals, and many more animals rely on them. Even the things that don’t eat krill usually eat something that does: albatross, leopard seals and killer whales are all indirectly dependent on krill.

Companies fishing in the Antarctic for krill usually market themselves as sustainable and trustworthy – as the good guys providing health supplements such as Omega-3 pills for clean-living individuals, along with fishmeal for farmed fish and pet food. But sustainability in the Antarctic ecosystem is a risky claim, when there is such patchy data, when the industry’s fishing overlaps with feeding grounds, and when the impact of climate change is already causing a decline in krill populations. History tells us that even species with huge populations can be driven to the point of collapse. In the 19th century no one would have believed that the most abundant bird on Earth, the passenger pigeon, could be hunted to extinction through the shooting of more than 5 billion birds.

Meanwhile the practice of transhipment means that catch is often transferred at sea to filthy cargo boats, or “reefers”. Many of these vessels are deployed in the Antarctic to allow the trawlers to remain at sea for months at a time, and their use has been linked to environmental and labour abuses.

But this isn’t only about protecting the Antarctic wilderness. With their bulbous black eyes and translucent pink bodies which reveal the green algae in their stomachs, krill not only underpin life in the Antarctic, but they also have a crucial role to play by helping to limit climate change. That’s because when krill gather, the ones at the top eat their fill at the water’s surface and then sink down to the bottom of the pack, before doing their carbon-rich business in faecal pellets which can drop to the bottom of the ocean. This is a vital process for cycling and storing carbon: as much as 23 million tonnes of carbon a year according to some studies.

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An EU proposal to create the biggest ocean sanctuary on Earth – 1.8m sq km, or 200 times the size of Yellowstone national park – will be considered by the Antarctic Ocean Commission when it meets in October. This Antarctic Ocean Sanctuary would cover much of the Weddell Sea and parts of the Antarctic peninsula. It is an area that the krill industry mostly does not yet fish, but is looking to expand into. Rather than letting something that belongs to us all be offered as an investment opportunity, more than a million people have already called for the protection of this unique region.

When a huge iceberg broke off the Larsen C ice shelf last year, it revealed an ecosystem that had been hidden for 120,000 years, providing an opportunity for groundbreaking scientific research. This year has also seen humans visiting parts of the Antarctic seafloor we have never been to before. What greater gift could we give to future generations than to preserve a bigger chunk of the natural world than we have ever done before? Krill might be tiny, but to protect the biggest beasts roaming the ocean we need to start small and think big.

• Chris Packham is a naturalist, nature photographer and author, and one of the presenters of BBC2’s Springwatch