Why is surface tension important to life on earth?

Surface tension is caused because water molecules stick to each other.

Surface tension is most prevalent in earth's most important compound, water. "Normal" water at ambient temperature has a high surface tension, but the addition of different chemicals can alter this.

The relationship between the molecules affects the fluidity of the liquid and it's ability to support pressure. For example, have you ever noticed how a paperclip "floats" on the surface of the water? If you look closely you might even notice the water being "stretched" as the paperclip floats on the water. This is a common example of surface tension, as the water acts like an elastic material.

Here is video showing the paper clip "floating" on the surface of water. Video from: Noel Pauller"

Without surface tension, even the smallest objects would sink underwater. The large particles of dust would not float on the water, but instead the particles would sink to the bottom and kill all of the marine life, causing the collapse of ecosystems.

Water particles at the atomic level help keep the cell membrane from collapsing on itself. Water is a critical component in cytoplasm (the jelly-like substance that fills the cell), this means that the surface tension of water allows the cytoplasm to hold-up the cell membrane. If the pressure is too extreme, then the water breaks down the cell membrane and the cell "drowns".

The high surface tension of water is also essential for processes such as water and blood transport in plants and animals respectively. The concave motion of the surface of the water allows it to be "pulled up" by plants from the ground.

Overall, surface tension is a necessary property that contributes tremendously to our lives. I have not even started to explain the relevance that surface tension has with modern technologies (raincoats, car wax, etc.).