What is a "drunken forest" and what does it have to do with the topography of eastern europe?

Mainly found in the tundra regions of Eastern and Central Europe, permafrost, a layer of perennially frozen subsoil, lies beneath the surface. Recently, permafrost, which is supposed to be continuously frozen, has been thawing in some places. The photo below is a picture of what is referred to as a "drunken forest." Because the trees roots are shallow, when the permafrost melts, the trees start to tip over. The melting of this permafrost throughout the Northern Hemisphere has been altering ecosystems and damaging roads and buildings across Russia and other countries of Eastern Europe.