The Green Planet - Seasonal Worlds

Taiga. The largest forest on Earth. 750 billion trees covered in snow all winter. Here is the northernmost border of the extraordinary world - the border of the Arctic Circle. To the north of it is land, most of the time shrouded in snow and ice. Three thousand miles south of the tropics - bathed in sunshine all year round. And between them is a completely different world, under the influence of ruthless changes. An endless cycle of four separate seasons - each with its own challenges. Short frosty days of winter give way to the urgent awakening of spring, and long hot summer days give way to the freshness of autumn. Opportunities are short term. Not only do plants need to be hardy and resilient to survive such fluctuations, but many of them have developed specific strategies to meet the demands of the seasonal world.