After a long, busy, and exhausting year, he wanted to take a rest in his summer house, which lies under a mountain opposite a nice, blue lake. He deserved this holiday. After parking his car in front of the oak trees, he opened the wooden door of the house. The scene he saw was not good at all. Spider webs were everywhere and dust had covered everything in the house. This was not the thing he had dreamed of. He was dreaming of a good holiday, not a holiday spent cleaning. He just left the door open and walked towards the lake to sit under a tree and take a fresh breath. He kept looking at the lake for a while and then, finding something interesting, he looked at the mountain, the forest, and the grasses on the ground. He started to talk to himself: "How? How could this happen? Even though nearly a year has passed, the lake, mountain, and grasses are as clean as I left them last year, but my house is a mess?" After thinking a little, he came up with a question he had never thought of in 50 years: "What makes nature so clean?"

I am sure that there are a lot of people who've found themselves in a similar situation to the man above. Unfortunately, most of us are usually not aware of the things happening in this universe. One of the things we tend to overlook is the cleanliness of nature. This is a topic which needs to be considered carefully, but I will just touch on some important aspects of this issue.

First, let's look at the oceans. The oceans cover three-fourths of the Earth's surface. There is a bigger world under the ocean than above it. This huge mass hosts jelly fish and tuna, dolphins and octopus, crabs and plankton, sea stars and sea plants. Currently, there are 120,000 species living in the ocean. This is just the number of the species, and doesn't account for how many variations there are within each species. When we consider the number of living organisms, there are millions of them. Every single day, lots of these organisms die. If there are millions of organisms and thousands of them die each day, then why cannot we see them on the surface of the ocean? Even if these dead organisms are very small, such as plankton, which has a size range from 0.2 m to 20mm, when millions of their dead bodies cluster on the surface, we should be able to see them. The answer lies in a perfect arrangement. For example, the job of cleaning the dead bodies of plankton (also the live bodies!) is performed by fish, sharks, and whales. A large percentage of the daily diet of these animals depends on plankton. Since these animals perform their job well, it is impossible to see any dirt that would have been caused by the dead plankton.

It might seem easy to get rid of the dead bodies of plankton, because they are small organisms. But what about big animals such as whales? What happens to dead whales? Let's consider the cleaning of dead whales. When a whale dies, its dead body sinks to the bottom of the ocean. This is called a "whale fall" by scientists. There are a lot of species whose diet depends on dead whales. In 1988, a group of researchers at the University of Hawaii found that there are at least 12,490 single organisms which supply their daily diet from a whale fall in the deep North Pacific Ocean. After bigger organisms, such as fish, finish their job, which includes eating the flesh of the dead whale, the other cleaners come to the scene to perform their roles. At this part of the fall, bacteria play a key role in cleaning the bones left from the whale fall. This is not as easy as it might seem. Actually, it takes several years to really clean the dead body from the bottom of the ocean. This is not just a cleaning process at all. While the whale fall is being cleaned from the bottom of the ocean, the ecosystem is supported by the energy from the dead whale.

This cleaning process is not only seen in the oceans, but also on the land. Even though it is more apparent than undersea, we are not totally aware of the cleaning process on land. Decomposition is the chain of events by which a dead organism breaks down to its smaller parts. We must stop here and ask this question: "What would happen if these dead organisms stayed on the land forever?"

So let's look at what happens to a dead animal on land.

When an organism dies, the process of decomposition starts shortly after its death. There are some stages in the decomposition of an animal. Shortly after the death of the organism, the enzymes in the cytoplasm of the cells start to break down the tissues. This process is called autolysis. It is one of the stages of decomposition in which bacteria plays a role. Bacteria start to break down the tissues. This is called putrefaction. Bacteria are not the only players who have roles in this process. Besides them, some fungi, insects, and even some carnivores are also involved. Live animals, water, air, and temperature (higher temperatures increase the decomposition rate) also help this process. During this time, fungi and bacteria, by using compounds from the dead organisms, convert carbon to carbon dioxide and organic nitrogen to ammonium (NH4+), and so they contribute to both the Carbon and Nitrogen Cycle. After this process is done, many organisms living in the ecosystem have benefitted. At the end of this cycle, soil is enriched with new nutrients which will help the new plants to grow up and the Carbon and Nitrogen cycles are enhanced.

By looking at the processes above, as well as other cycles (e.g. the Carbon cycle), it can be said that the Earth has its own recycling system. While modern societies have only recently understood the importance of recycling, Earth has been using this system thanks to the arrangements given to it.

The things shown here are just some examples of the extraordinary systems existing on the Earth. These systems have always been like this, since the very beginning of the universe. These perfects systems in nature perform their tasks without any human help. The only thing for us to do is to appreciate this harmony, understand its value, and keep it going for the next generations.