Unfortunately you cannot. In fact, you should carry both a valid Canadian passport and a valid American passport every time you want travel between them.
The following certificates are considered to be a proof of Canadian citizenship:
A Canadian birth certificate
Certificate of Canadian citizenship (the ones issued up to 1977 are called...
Canada would be the same as any country that didn't have 'nature'. If any country had no 'nature', they simply could not support human habitation. To suggest that Canada offers nothing but 'nature'...