Donating to wildlife charities is all well and good, but going there additionally provides income and jobs for local persons in the immediate area - instead of them relying on the forest to try and make a living, cutting wood, converting it to maize, turning it into charcoal, etc, they instead see possibilities to offer accommodation at all levels from backbacker upwards, guiding, local cafes, etc. In most countries, a portion of income from tourism is also given to the local community (in Uganda it is 20% of permit fees) - call this a bribe, call it it an incentive to protect, no difference, it works - communities want to protect the natural resources. Local communities need to see direct benefit in order to become involved in the solution, not the problem. Going there provides income at all levels. And it is not small isolated pockets of land we are talking about, it is vast amalgamated plots, running up against each other and to adjacent national parks.
Additionally, if we move further south, vast tracks of the Zambezi Valley, the hinterlands of Krugar, etc, are (as I said before) being protected not by government or charity, but by landowners seeking to make a profit out of conservation. Are you going to donate (to private companies that are in it for profit) the many thousands needed to continue the work? I doubt it, better let them charge their wealthy clients several hundred dollars a day for the pleasure of visiting. I don't think the ecosystems and associated animals worry too much that it is capitalism that is maintaining them, neither do I.
Plus, maybe you are more generous than most, but persons travelling to these areas tend to pay much greater amounts than those simply donating.
I have warned Neil that I may up sticks and leave him for a year or so (with the freezer full so he doesn't starve! 
