Why is gimp using so much memory? Is there any way to reduce this?

[Ofnuts]

In the low-precision 8-bit/channel Gimp uses 4 bytes per pixel, so a 1000x1000 image is already 4MB. Repeat for each layer, plus each undo history step (which is mostly keeping a copy of the layer(s))... In the preferences you can reduce the undo "depth" and the tile cache size (which is basically how much RAM Gimp can use), but this can quickly get uncomfortable (if you limit the RAM Gimp will swap to disk).