A baby king penguin was under attack by a southern giant petrel. This is a scene from a documentary that brought suspense and broke the hearts of many viewers. When the giant petrel, which had been looking for an opportunity, attacked the baby king penguins, one of the baby king penguins ran up to the cameraman as if it was asking for help. Trembling with fear, it held the camera stand with its wings and begged him. But the camera crew couldn’t do anything but keep watching the situation, because as observers they couldn’t go against the ecosystem, the great law of nature.
The giant petrel attacked baby penguins for a reason: they had their young waiting in their nest. If a mother giant petrel failed to find food, its young wouldn’t have anything to eat. Both the penguins that wanted to live and the hungry giant petrels are the members of the fierce ecosystem where the relationship of eating and being eaten is an invisible principle.
The food chain of eating and being eaten
The living creatures that live in the ecosystem have a relationship of eating and being eaten. The grasshoppers that feed on the grass are eaten by frogs, and the frogs are eaten by snakes. The predator-prey relationships of the ecosystem are connected like a chain. That’s why it is called the food chain. As most living creatures in the ecosystem eat various kinds of food, the food chain is entangled complicatedly that it’s also called the food web.
The food chain is a process of transmitting solar energy through the relationship of eating and being eaten. The green plants which synthesize organic compounds, using inorganic compounds and solar energy, are called the producers, and they become nutrients for other organisms. Animals that eat the organic compounds produced by the producers are called consumers. Consumers are divided into three different categories: primary consumers, secondary consumers, and tertiary consumers. Primary consumers or herbivores are the animals that eat plants; secondary consumers are the animals that feed on herbivores; and the tertiary consumers are larger predators. When any organism dies, it is broken down by decomposers, and turns into inorganic compounds and is absorbed by plants again. Typical decomposers are bacteria and fungi like mushrooms. The food chain does not end by top predators, but it goes back to producers through decomposers; it makes a big circle.
Ecological balance maintained by the profound providence
The vast African savannas are full of mysteries of the beginning. We see lions enjoying a peaceful nap in the shade of trees under the scorching sun. Are the lions—top predators—kings here?
Whenever July comes, hundreds of thousands of gnus move from Serengeti in Tanzania to Maasai Mara in Kenya. They constantly move to find more abundant grass and water. Then lions have no choice but to move, following gnus—their food. Ironically, the vast grasslands move according to plants that are on the bottom of the food chain. The world of wild animals is a place controlled by the profound providence, not by endless competitions or the law of the jungle.
Lions, the top predators, hunt once every three or four days. If lions kill gnus indiscriminatingly even when they are not hungry, only predators like lions will be left in African savannas, and they will have to walk the way of co-destruction. The lions that feed on the gnus know by instinct that they cannot survive either if all the gnus die.
Whether it is grass or lions, they die after some time. Nevertheless, the land does not get filled with dead animals or dead plants. This is because there are decomposers. Decomposers like worms or mites divide the dead bodies, which are organisms, into big pieces, and microorganisms such as fungi and bacteria decompose organisms completely into the form of inorganic matters, which is the form that the plants can use. The inorganic matters made by decomposers are used for photosynthesis of the plants, and organisms made by plants move along the food chain and go back to soil by decomposers. This is the material cycle in ecosystem.
Even if a certain species decreases dramatically due to a sudden change in the situation like a natural disaster, its number gets restored little by little and keeps the ecosystem in balance. For example, in a food chain of grass, grasshoppers, frogs, and snakes, if the number of grasshoppers decreases suddenly, there will be more grass, which is the food of the grasshoppers, and the number of frogs and snakes, the predators that eat grasshoppers, will decrease one after another. However, when the number of grasshoppers increases again, the amount of grass will decrease, and the number of frogs and snakes will increase—it will all come back to the original state. But the ecosystem has a food web that is more complicated than this. Therefore, it can keep its balance, because even if a certain species decreases, other similar species can replace it. The ecosystem which has a complicated food web has ability to keep its balance and control itself safely.
Torn food web
However, ecological balance breaks if there is an extreme change. In most cases, the ecosystem destruction begins with humans.
The ecosystem sometimes falls into disorder as people bring animals or plants to a region that is not their original habitat, either by accident or on purpose. Oneseed bur cucumbers (or sicyos angulatus) are easily found around streams in Korea. It was first brought into Korea from North America to use it for grafting, but now it has spread all over Korea. As it persists in growing and is prolific, other plants cannot survive wherever oneseed bur cucumbers settle. Coypus (or nutrias, nicknamed “monster rats”) mess up the ecosystem as they are increasing rapidly. Korea brought them in from South America in 1985 to use them for fur and food. However, as they were in disfavor, farms gave up on breeding them. As a result, they have dominated the ecosystem with their great appetite and high reproduction rate. The food chain is collapsing as the indigenous ecosystem is encroached by the introduced species.
Everglades National Park in Florida, U.S., is struggling with Burmese pythons. These snakes native to Southeast Asia were brought into the U.S. as pets. However, as the owners got bored of them and threw them away, they started to conquer the ecosystem very fast. Burmese pythons have no natural enemies and they eat even crocodiles and deer as well as small animals such as mice and rabbits.
Achim Steiner, the executive director of the United Nations Environment Programme [UNEP], announced in 2010 that the estimated annual damage from invasive species worldwide totaled more than 1.4 trillion USD. The whole world is suffering from ecological disturbance caused by introduced species.
Moreover, the food web is being torn as many plants and animals became extinct due to environmental pollution, global warming, indiscriminate poaching, etc. The case of dodos showed the danger of extinction for the first time. They used to live in the island of Mauritius, east of Africa. Europeans, who arrived in the island of Mauritius in the early 16th century, hunted these flightless birds wildly, and the number of dodos decreased as time passed. The last dodo was found in 1681, but after that, dodos became extinct. Then, on the island, calvaria trees started decreasing suddenly. It was because dodos, which used to help calvaria trees sprout by eating their seeds and excreting them, disappeared. The extinction of one species can cause the extinction of other creatures like dominoes.
We can understand what a great danger the ecosystem is facing now through the International Union for Conservation of Nature [IUCN] Red List of Threatened Species. It has assessed about 74,000 species among more than 1.7 million registered living species on the earth. The result says that around 20,200 species are endangered, and 10,000 of them are plants. By taxonomic group, 40% of gymnosperms, 26% of mammals, 13% of birds, and 41% of amphibians are threatened with extinction. Considering that the number of assessed species is very little, it is estimated that the extinction of the living creatures on the earth is a lot bigger in scale. According to the World Wide Fund for Nature [WWF], about 10,000 species go extinct every year including the species that haven’t been found yet. Stuart Pimm, a conservation biologist at Duke University in the U.S., says in concern that species are going extinct 1,000 times faster than before the development of civilization, and we are going to face the great extinction.
From the beginning, all the living creatures on the earth have been keeping their balance through the food chain according to the invisible principle. The ecosystem, where the living creatures are connected to each other and keeping their balance exquisitely, is marvelous.
The ecosystem is more peaceful when humans don’t involve themselves in it. None of the members of the ecosystem is unimportant. They influence and are influenced by each other. They go with the flow without becoming greedy. It is because they know very well predators that make other species extinct will destroy themselves. It is only humans who always forget this fact.