If all the seawater on Earth becomes fresh water, will human life be better? The blue planet may no longer have vitality

As we all know, the Earth on which we live is a very special planet in the solar system, also known as a blue planet, with the ocean area accounting for 71% of the Earth's surface. According to statistics, there are a total of 1.386 billion cubic kilometers of water on Earth, of which seawater accounts for 96.5% of the Earth's total water volume, or 1.337 billion cubic kilometers, which is simply an astronomical figure.

To make it easier to understand, let's make a simple analogy. If we collect all the seawater on the earth and form a sphere, the diameter of the sphere will be 1,367 kilometers. Unfortunately, such a vast ocean cannot be directly used by humans due to its high salinity, such as drinking or irrigation. The amount of salt in the ocean may exceed your imagination. If you evenly distribute it on all the land on the earth, it is equivalent to a 40-story salt wall. Therefore, some friends say that it would be great if seawater could be turned into fresh water.

If seawater can really become fresh water, what will happen to the earth? Will it really be as good as everyone expects? It's really not. There are several reasons.

First of all, this is a disaster for marine life. According to statistics, there are more than 15,000 known marine fish species in the world, and 210,000 known marine species. Scientists estimate that there are about 2.1 million species of marine life. Marine life has adapted to the saltwater environment in the ocean. If seawater becomes fresh water, it will inevitably cause large-scale extinction of marine life.

The picture comes from Tuchong.com

The second reason is that it would affect our weather and temperatures. The extinction of marine life would cause a drop in oxygen levels in the air. This is because algae in the oceans produce most of the oxygen on Earth. Saltwater fish and other marine life have evolved to rely on saltwater to stay hydrated and to be able to remove excess salt. Not all marine life can do this, but being able to remove excess salt is essential to survival in the ocean. Some species, such as salmon, have adapted to both fresh and saltwater, but in most cases, all saltwater species would be extinct, including underwater algae. They account for half of the Earth's photosynthesis, which plays a vital role in providing the Earth with oxygen. Plants convert carbon dioxide in the atmosphere into air we can breathe, so without algae, not only would we have less oxygen, but the atmosphere would retain more carbon dioxide, which would increase the greenhouse effect and make some areas of the Earth extremely hot.

The third reason is that it affects the convection of the entire Earth system, helping warm water from the equator move northward, while cold water from the north cools the hotter areas in the south. At the equator, warm water can carry more salt, so denser water sinks lower, while cooler water flows on top. Without salt, the whole process would break down, the ends of the Earth would freeze, and the weather near the equator would intensify, hurricanes would be more frequent and deadlier. Imagine if photosynthesis was significantly reduced, and the climate was either extremely cold or extremely hot, then our world would no longer support the diverse plant life it has today, the entire plant chain would collapse, and most species would become extinct, and of course we humans would be no exception.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Dong Hanwen

Reviewer: Zhang Yuxiu

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.