The world is deep in a period of glaciation. 5 million AD, the planet is once again dominated by icecaps, as it was in the Pleistocene epoch, 2 million BC. So much water is locked up in the icecaps that global sea levels are nearly 500 feet (about 150 meters) lower than they were during the Holocene. Ice sheets over a kilometer thick cover most of North America and the whole of Scandinavia, reaching down into Northern Europe.
Where once the craggy coastline of southwest Great Britain boasted semitropical plants which flourished in coves warmed by the Gulf Stream, there is now blizzard-swept tundra. The continental shelf which spreads out from the British Isles and France is an exposed, frozen plain of sand and gravel deposits (outwash from the glaciers) and frozen soil. On a winter's night, temperatures fall below -76 degrees Fahrenheit (-60 degrees Celsius) and wind-chill makes it feel even colder.
Come the brief summer, conditions improve a little. The edge of the icecap lies sparkling to the north, its meltwater running in gravel-choked streams across the flat tundra. Water collects everywhere in lakes and ponds, unable to drain away through the permanently-frozen subsoil, or permafrost. Rocks lie in polygonal patterns, covering broad expanses of land. The bitter, boulder-cracking frosts of winter have heaved when up from the soil in successive freeze-thaw cycles and rolled them together in curving lines. Dome-shaped mounds, called pingos (or hydrolaccoliths), rise up from the tundra. Formed around a core of ice, a pingo occurs where deeper water has sprung through the permafrost or in sites where lakes have progressively frozen from the sides towards the center.
Despite the harsh cycle of fierce winters and brief summers, there is life here. The permafrost does not favor deep roots, but certain forms of flora are tough enough to eke out an existence from the frozen soil. Clusters of cotton grass border the lakes, undulating meadows of small, hardy lichens and grasses cover the raised land between the gravel deposits and streambeds. Tight clumps of heather form a rooting site for many varieties of small flowering plants. The only plants which might be considered trees are closer to shrubs, and even these hug the ground. Species of willow send their gnarled trunks horizontally and spread their branches across the earth, as if unwilling to raise their heads into the bitter winds that will inevitably come with winter.
When spring arrives in Northern Europe, water from melting ice runs in narrow, muddy torrents between the banks of shingle that choke the riverbed. The thaw softens the surface soil and turns large areas of the tundra into marsh, dotted with pools. Because of the climate conditions, the fly lifecycle is accelerated: they mate and reproduce in an incredibly short period of time during the brief thaw. Migrant birds wheel in and out of the swarms, making the best of the bonanza. Migrant birds fare particularly well here. They weather out the winters in less extreme regions further south and travel to these bleak lands in the fleeting summer months to take advantage of the quick and intense growth cycle of the flies.
The spring sun will slant through the clouds of insects (including bees and butterflies), illuminating the reddish fireweed, the yellow, powdery male flowers of the low willows and the white heather bells. All these plants grow in shallow pockets of soil, in contrast to the orange and yellow lichens that coat the frost-shattered rocks.