Hi There, I was preparing for a class where I compare salmon in our ecosystems to the keystone in an arch, if you remove the salmon the ecosystem collapses! I have never actually seen a keystone as I live in Alaska and everything is new and of less than cheesy construction-besides what nature built! Anyway, i googled and got your web page and THANK YOU! Beautiful pictures. With your permission I would like to use your arch shot ti ukkustrate my point. I will credit the photo to you.