Change

In the wetlands a difference in elevation of just a meter can change the nature of the ground from wet to dry.  This has dramatic impact on what will grow and what will not.  Within a couple meters one elevation can grow grasses and the other trees. The difference in ground level leaves one submerged in water the other on dry land.  Thus when something changes and the water lowers or rises one of the occupants is sure to suffer.

I expect that it is within this context that we saw the remains of trees that once flourished and now are simply skeletons.