soon he hopes to see at least 25 more seagardens in the us. from fisherman to farmer.h now does his part to protect the ocean. reporter: now we head to southern africa, home to the rhinoceros. most of these large land animals are native to zimbabwe, kenya, namibia and south africa where there are around 21,000 of them. but it used to be far more. since the turn of the century, there's been a huge rise in rhino killings. the global black market in rhino horn is now a billion dollar business. traders receive an average of $60,000 u.s. per kilo of horn. but while the battle against poachers is certainly challenging, it's not hopeless. >> africa was once populated by hundreds of thousands of rhinoceroses. africa's national parks have had to ramp up security because more and more poachers are heavily armed. the fight against poaching is turning into a war. the rangers in south africa's kruger national park don't want to be recognized out of concern for their families' safety. >> from years back rangers used to focus more on environmental stuff and with time there seem to be