No one in Africa would pay to reduce Taipei's pollution. The rhino is not like the whale. The whale needs protection because it lives in an unowned ocean. Without cooperative international protection, it may be hunted to extinction. But rhinos live on land.
Someone owns the property they inhabit.
It is the task of the government of the country in which the Rhinos live to enforce the laws necessary to keep their rhinos alive, just as it is the task of the ROC government to enforce the rights of Taipei citizens to clean air. Finally, let us not worry about the extinction of the rhino population due to speculation and the high prices of horns. Unlike oil and other fossil fuels, rhinos can be reproduced. It takes quite a bit longer to produce a rhino than it does to produce a chicken. But if the price of rhino horns is high enough, entrepreneurs will find a way to begin to raise rhinos for a profit.