Using google I've come up with a different solution as seen here:
This happens for both ram and vram. The best thing to do is to change the editor settings to show the stats and pay attention to the memory usage. Go to editor settings>type "show frame rate and memory">click the checkbox. Now you'll see the stats in the top right of the main editor window. If the memory get's beyond a certain amount, then save>close editor>reopen editor.
A little snippet from the foum thread:
"The editor is absolutely horrible about respecting physical ram and will leave all sorts of memory tied up for no reason (probably undo history, if I had to take a guess). Doing anything with large landscapes, like a change to a material that is used across all components, is one way to blow out your ram because it has to recompute all the shaders and the editor thinks it's a good idea to just allocate 200000000000gb of ram all at once to do it, rather than sequentially chunk it out into small pieces of ram at a time. One reliable way to explode your ram is to make a large landscape and then import layer data from a png or something(world machine splat maps are an example). Do that for 5 or 6 layers and you'll see the ram start climbing up to ridiculous levels."