Our knowledge of our immediate surroundings – of 'nature' – is declining. The reason for this decline in knowledge of the environment (and not just some idealised 'nature': cities are full of fascination as well, if you only take the time to walk through them) is simple: time. A human childhood, to age 15 and allowing 12 hours a day, is about 65,700 hours: the amount of time a child has to spend on anything is limited by the amount of time they have to spend on everything else. In 1913, when my grandmother was six, she spent a lot of time outside because there were few other demands on her time: school, books, playing with toys perhaps, chores. In 1968, when I was six, there was school, books, many more toys, chores, the radio, and TV. In 2013 there are school, books, really a lot of toys, chores, video games, and the vast sink of life that is the internet.
It would be astonishing if a child of the early 21st century knew as much about their physical environment – be it 'nature' or the city – as one of the early 20th, because it would mean that they had somehow stretched time.
Whether this is something to worry about depends on whether you think the physical environment matters, and whether you think the things competing with it for the scarce hours in children's lives matter: is facebook and TV more important than picking blackberries, because the time you spend on one eats the time you can spend on the others?