How to smooth terrain to lower polygon count?

How to smooth terrain to lower polygon count?

I'm using Unity. 
I've created a simple Beach using Terrain editor. 
The problem is that Stats show me already a lot of Triangles only for Terrain renderer: 40K . 
So my question is: how can I create a Unity Terrain suitable for Mobile game ?
How can I smooth terrain edge ? 
Thanks

Solutions/Answers:

Answer 1:

If you select your terrain and go to the last tab which is settings you will see a slider called ‘pixel error‘. That determines the accuracy of the mapping between the terrain maps and generated terrain. The higher the value, the lower the accuracy and rendering. The default should be about 5 which is why your number of tris is so high.

Increasing this slider should lower the tris and the rendering.

There are also resolution values you can alter, but they may lower the quality without affecting the tris like you want.

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References