I don't think any human society is prepared to make decisions which they may not like if they're made by people who don't speak the same language... … - David Attenborough

Just as the human population was starting its unprecedented growth spurt in the late eighteenth century, this was published. It's a first edition of an essay on population by the English clergyman Thomas Malthus. Malthus made a very simple observation about the relationship between humans and resources and used it to look into the future. He pointed out that "the power of population is indefinitely greater than the power of the earth to produce subsistence for man. "Food production can't increase as rapidly as human reproduction. Demand will eventually outstrip supply. Malthus goes on to say, if we don't control human reproduction voluntarily, life could end in misery, which earned him a reputation as a bit of a pessimist. But Malthus' principle remains true. The productive capacity or the Earth has physical limits and those limits will ultimately determine how many human beings it can support. m10s58-m12s18

In Rwanda children inherit land from their parents but in a country where the average family has more than five children that can only mean one thing – smaller parcels of land to live off. m30s00-m30s12

Without thermals, [raptors] can't travel far. But the snow geese fly on... They navigate by the stars.