agree with what jrista said. the 10-22 is a very interesting lens for some types of nature photography, but a very limiting lens that precludes a lot of potential images. I would not consider it as a primary (or only) lens. I definitely would want something like that in my bag -- but it'd be my third or fourth lens, not my first or second. Coverage of the 20-70 range would be the critical range for much nature photography, unless you want to specialize in animals/birds, and then something like the canon 100-400 would be my starting point. The 10-22 is more of a specialty lens that creates some interesting types of images, but it's not one that I'd ever see as my go-to.
To me, the key ranges for nature photography are 20-70, then 100-200, then 300-400, then 10-20, then 500 and higher (until you run out of money). Below ten you're in fisheye range, you either get a kick out of working with one or not. Somewhere along the way a macro lens or two get added (I use a sigma 180). You'll cover 90% of your needs with 20-150, unless it's running away from you or flying, at which point the 100-400 becomes more important.
Don't forget that for very wide style landscapes you can do a lot with a normal lens and some stitched pano. I was going crazy for a while trying to figure out how George Lepp did some of his landscapes I loved, and when I finally got to talk to him, it turns out they were all done around 70mm vertical and stitched panos. he does a LOT of stitched panos in his work...
I do primarily nature, and a lot of bird photography. I currently carry a 28-300 (which I'm going to upgrade, bought it as a street kit carry around and it's okay, but I really would prefer something wider and not so superzoom, because the superzooms aren't as sharp; nice lens, not killer lens), and my 100-400, which is my go-to. and a Sigma 180 macro, and a 300/F4 with a 1.4x tied to it most of the time. I use the 100-400 handheld, and the 300/1.4x on a tripod. It's sharper, but less flexible. There are times when I'd kill for a 10-20, but I've also found much of the time I can use my standard zoom and do panos... buying a 10-20 is on the list, but not near the top of it.