[Smart Farmers] Looking at the Wandering Earth from an agricultural perspective: If the Earth were wandering, what would humans eat?

Editor’s Note:

The recent hit of "The Wandering Earth 2" has aroused deep thought behind the sci-fi blockbuster: the doomsday scenario assumed in the movie is far-fetched, but if the earth reaches the "doomsday", what will humans eat? Popular Science China Smart Farmers has launched a series of popular science articles, welcome to follow.

After the hit of The Wandering Earth 2, many people have raised the question: What would humans eat if the Earth came to an end? Obviously, we are talking about hypothetical situations. However, many people do not know that humans are doing a lot of preparation for this hypothetical situation, and biodiversity conservation is one of the most important tasks.

We all know that biodiversity supports our health in many ways. In addition to providing us with fresh water and food sources, it also provides us with important medicines and resources for medical research.

Biodiversity also helps improve human safety and security. It can play a role in controlling pests and infectious diseases. It can help protect us from the worst effects of natural disasters by supporting healthy ecosystems, such as those that provide shelter from floods and storms, and protect hillsides from erosion or avalanches. In critical moments, biodiversity can provide food security for people facing drought or famine.

To this end, a global seed bank has been built in Svalbard, Norway, which is the ultimate safe place for crop diversity. On a frozen hillside within the Arctic Circle, countries around the world store their collected samples here as a safety backup to avoid the impact of hurricanes, floods, power outages and wars. So far, more than 500,000 seed samples have been stored. Whether these seeds will be needed is anyone's guess. However, scientists believe that if the earth experiences a catastrophe, this seed bank can provide seeds for the recovery of all things on our earth. This possibility may be remote, or perhaps not so remote.

The Svalbard Seed Vault is built in the mountains of Norway. Image © Global Crop Diversity Trust

Some people may ask, if the seeds of crops are preserved, what about animals? I think the ocean may be the largest and best shelter for animals. According to scientists, life originated in the ocean about 3.5 billion years ago. Many animals and plants originated in the ocean, and some animals and plants lived on land and returned to the ocean. Whales are representatives of animals that returned from land to the ocean to eat fish, and dugongs, which we call "mermaids", are animals that moved from land to water to eat grass.

The underwater world under the sunlight provided by Liu Yadan

The ocean world is home to a variety of beautiful creatures and is also a bustling world. There are countless animals and plants in the ocean, with various shapes and colors. At present, we know of 210,000 species of marine life, but it is estimated that the actual number may be more than 10 times. According to a survey report that integrates global marine data, there are currently 15,304 species of marine fish recorded, and it is estimated that there will be about 20,000 species. Since the start of the marine census in 2000, an average of 3 new marine species have been discovered every week. In addition to marine fish, shrimps and crabs, there are also shellfish, seaweed, sea cucumbers, sea urchins, squids, jellyfish, dolphins, etc. Along with these aquatic animals, there are more than 70 species of seaweed, more than 4,000 species of seaweed and more than 9,000 species of corals. They are brightly colored, swaying with the waves in the water, blooming like flowers, and constructing underwater grasslands and gardens, becoming an important home for thousands of animals and plants to survive.

Joyous Ocean Provided by Liu Yadan

So, let's get back to the topic. If the world ends, what food can the ocean provide us? The answer is definitely some of the most resilient creatures.

What is the most resilient animal in the ocean? Many people will immediately think of killer whales, great white sharks, tiger sharks, mako sharks, giant Pacific octopuses and other sea giants. However, scientists will also answer that these top animals that dominate the ocean are not necessarily the animals with the strongest vitality and the strongest ability to survive.

On the contrary, according to the International Union for Conservation of Nature (IUCN), hundreds of marine species are endangered and critically endangered around the world, including large aquatic organisms that we are familiar with. Many of them are already in danger before the end of the world, and I am afraid that by that time, we will have long lost their traces!

Why? The reason is very simple. First, these large mammals living in the ocean, in addition to cetaceans, also include seals, walruses, sea lions, etc. Due to their large size, they need a lot of food. Human activities, climate change, and marine pollution have caused changes in the food chain in the ocean. They may be the first to fail to survive. In addition, these "big guys" have a long reproduction cycle, and the population recovery speed often takes a long time. Not to mention the drift of the earth, even if there is a disaster in the ocean, they will be the first to be seriously affected. It is worth mentioning here that the largest fish in the existing ocean - the whale shark, the largest aquatic mammal in the existing world - the blue whale, the largest turtle in the world - the leatherback turtle, and the only marine herbivorous mammal - the manatee.

The blue whale is the largest animal on earth. An adult blue whale can grow up to 30 meters. The largest individual on record is nearly 34 meters long and weighs about 180 tons, which means that a blue whale weighs about 30 elephants. However, in the past 150 years, the number of blue whales has dropped by 90%, mainly due to human hunting. It was not until 1966 that the international community banned the hunting of blue whales, and their number gradually increased. It is estimated that there are less than 4,000 blue whales in the world's oceans.

Sirenia is a very special group of marine mammals, and is the only herbivorous mammal in the ocean. Interestingly, it shares a common ancestor with the Asian elephant on land. The dugong, known as the mermaid, is one of the sirenians. However, recent studies have shown that dugongs are functionally extinct in Chinese waters. The last sighting in China was recorded 14 years ago. Although most people have not seen mermaids in person, her beautiful image is not lacking in ancient documents, legends, fairy tales, or modern poems, stories, and film and television works, carrying the beautiful childhood fantasies of many generations. The disappearance of the dugong makes us even more heartbroken.

Second, for a long time, human beings have been endlessly demanding marine resources. Especially with the improvement of modern science and technology and the intelligence of production tools, the development of marine resources has intensified, causing some creatures living in the ocean to suffer unprecedented survival crises, and some have even become extinct.

Most of the fish we like to eat are large, slow-growing fish (like cod, tuna, and snapper). As populations of these fish decline, fishermen are changing the species they catch. Increasingly, they are targeting smaller fish closer to the bottom of the food chain (like mackerel and sardines). These smaller fish can be prey for larger fish, so removing them threatens the recovery of the larger fish.

An example is cod fishing in Norway. As cod populations declined, fishermen began targeting poutfish. Poutfish feed on krill and copepods. Krill also feed on copepods, as do cod larvae. As poutfish were caught, krill increased, causing copepods to decrease. The cod larvae then found it difficult to find food, making it more difficult for cod populations to recover.

Bluefin tuna is another example. Atlantic bluefin tuna is the largest fish in the tuna family, with a record of up to 3 meters long and a weight of about 400 kilograms. Bluefin tuna is a favorite gourmet fish for many people. It has delicate meat, rich fat, light red meat, excellent taste, and is very expensive. However, since the 1960s, the catch of bluefin tuna in the world's oceans has greatly decreased. According to an international public survey report in 2019, the population of bluefin tuna in the ocean is less than 10,000, and it has become an endangered species!

Photos from the Internet

Having said so much, what creatures in the ocean might be left for us to eat at the end of the world? I think they are neither the giants of the sea nor the rotifers, turbellarians, water bears and lighthouse jellyfish with super survival ability. Although they have their own special functions, they are too small to use them as food to fill our stomachs. Therefore, at the end of the world, if our Noah's Ark is drifting on the sea, I will introduce several aquatic creatures that may survive and can be used as food by humans. They are: smart octopuses, Antarctic krill, the granary in the water, smiling electric rays, strange-looking anglerfish and parasitic host remoras. However, the premise is that before the end of the world, biodiversity protection is well done and they are not eaten up by humans!

Produced by: Popular Science in China to Benefit Farmers

Producer: Guangming Online Science Department

Author: Liu Yadan, Researcher, former Assistant Secretary-General of the Chinese Society of Fisheries and Chief Scientific Communication Expert of China

Planning: Wu Yuetong, Xie Yun