cecilia kang and eric rasmussen-schumacher, thank you. >> brown: next, a milestone for planet earth. on monday, the world's population will officially ach seven billion. what does that mean for people and planet? we begin with this report from lawrence mcginty of "independent television news." >> zack rya came into the world at the rosie hospital in cambridge. around the world, three other babies were born in the same second. first the figures. it took all of human history up to 1804 for the world's population to reach 1 billion. but the next billion came only 100 years later, in 1927. and after that, the rate of growth accelerated. 3 billion in 1959. 4 billion, 1974. 5 billion, 1987. 6 billion 1999. and now 7 billion. we're adding a billion population every 12 years. moplation growth will not be even around the world. in africa for example, the current population of 1 billion will increase to 3.6 billion by the end of the century. but in asia, yes, population will increase from its current 4.2 billion to 5.2 billion by 2050. though by the end of the century it will fall to 4.6 billi