Which Camera for trekking in Peru?

Is this really a question than needs a long response? It's the most expensive but will give you very high quality images - 14.2 MP with a large CMOS sensor. Good lens. If you have the money then G1X it and have the best images. 

G1X is many a professionals point-and-shoot. 

G12 is the previous generation. G1X has replaced it.

SX40 is a toy. It might look like a DSLR but it's a gimmick though has crazy zooming power.

IXUS 510 HS very much a point-and-shoot fun camera. Does it even let you shoot raw?

Sx40 - size boy like dslr.. you will have more zoom. Pics quality will be like g12 , or worster.

G12 - buy used. Because this worster than S100 or buy Canon powershot S100. quality pretty good. low zoom.

G1X - Best quality pics of all., almost same as DSLR.  low zoom. price..

510 HS - for begginer photographer, no manual settings, quality not very good - i do'n't recomment it..

If you choose Sx40 - you can zoom 35x , capture more things, with normal quality.

canon_powershot_sx40_hs at www.efoto.lt

canon_powershot_g12 at www.efoto.lt

6781703258 at www.flickr.com

I think for travel you will love the long zoom of the SX40.  It will get you close to things you can't reach by foot.  I was amazed the first time I shot the moon with mine.  At full 35X zoom, auto setting, hand-held, I can see the craters very well.  Think how great it will be for shooting birds in trees, etc.  It is also very good for macro.  Good luck!

I have had this camera and for the exact reason... traveling, need for a small and easy to carry camera, feature rich, and a decent video quality. 

Canon sx40 for me is the best value for money with the best characteristics you want your camera to have for your trip .A little beat heavier from the other 3 but it's worth it.

Travel = bigger zoom so going for Canon Powershot SX40 is understandable 

Canon Powershot SX40  for its great  zoom.

Compact (DSLR features) amazing in low light and the video is awesome!