As we travel south so the sun's influence grows stronger, and at 50 degrees of latitude, a radical transformation begins.
Summers here are long enough for broadleaf trees to replace conifers.
Broadleaves are much easier to eat and digest.
So now animals can collect their share of the energy that has come from the sun.
It's summer and these forests are bustling with life.
But the good times will not last.
Broad leaves must be shed in winter for their damage by frost.
As they disappear, so the land becomes barren with little for animals to eat.
The inhabitants must migrate, hibernate, or face months of near starvation.
The Amur leopard - the rarest cat in the world.
