The ethics of tourism is a little more complicated than travel CO2 alone.
The vast majority of people in the developing world have far lower CO2 emissions attached to their lifestyles that even ethical* westerners. A big deal is made of carbon trading; are these people not entitled to a little "extra" CO2-by-proxy for what is often a major source of income and social change for them?
Add to this the fact that the alternative to tourism isn't just "no tourists", but instead inefficient and environmentally harmful agriculture and livestock practices, as well as poaching. The game park lands are often marginal to begin with (which is why they were left wild in colonial days), at least in Southern Africa.
By which I don't mean that all tourism is good, but blanket statements that such trips are by definition unethical are also not entirely justifiable. Go for longer periods than the jet-setters, save up and be willing to spend, take care what you spend it on, and global tourism is a perfectly ethical possibility.
The eastern half of South Africa, Kathy. Take a guided walking tour through one of the big parks. On foot the big animals are too difficult to find and scary if you do, so these trips often concentrate on smallandinterestingthings. Meerkats are at least as cool as lemurs, IMHO. Often the trips come with camping goodness too. The Wild Coast in what used to be the Transkei is also a great area for off-the-beaten-track stuff. Or Namibia, as MV says.
*Almost regardless of how you define ethical.
