From a low flying plane, at the right time of year, the ti ndra land looks like a rich carpet from faraway Araby. The rainbow patterns are woven by wild flowers wafted by breezes under the vivid blue of the summer sky. But summer is shoat and this gay scenery soon disappears. For the tundra sleeps through the long, sunless Arctic winter under a light blanket of snow.

The Northern and Southern Hemispheres both have their tropics, their temperate climate zones and polar regions. But only the Northern Hemisphere has a tundra region. It is a narrow belt circling the top of the world where the far, northern shores dip their toes into the icy Arctic Ocean.

There are strips of tundra along northern Alaska and along the far north of Europe and Asia. Some of the off shore islands in the Arctic Ocean also suffer through the cold, bleak winters and enjoy the short, bright summers of a tundra climate. Almost all this tundra is within the Arctic Circle.

For most of the year, the weather is freezing and in the mid winter months, the sun never rises. A thin layer of mosses and lichens, a few scrubby bushes and billions of plant seeds sleep under the snow. Billions of mosquito eggs also sleep here through the long winter night.

Spring comes late. Dawn breaks and each day gets longer until by mid summer the Arctic sun does not set when each day is done. The weather is between 40 and 50 d ogress, warm enough to melt the snow anda few feet of the frozen ground. Puddles of water stand on the boggy swampland and the sleeping plants and animals wake up to Sreet the tundra summer.

The air hums with clouds of insects and flocks of migrating birds fly in from afar to devour them. Dozens of different bright alpine flowers burst into bloom. Rabbits and reindeer come to feed on the mosses and grasses, foxes and polar bears prowl through the scrubby bushes. And the summer tundra is a nesting ground for the tern and many migrating birds.

Most of the tundra is flat lands, but some of it marches c ver gentle hills and up the lower slopes of rugged mountain ranges. The climate is never hot, but the short summers are warm enough to support a teeming population of wild plants and animals. But the ground never thaws deep even for the roots of a tree   and the tundra is without trees and forests.

Polar seas tend to be warmer than polar lands   which is why we have no tundra region in the Southern Hemisphere. The South Pole is on land covered with spreading glaciers which face the seas with steep cliffs of ice. The North Pole is under the Arctic Ocean and in summer, its waters are just warm enough to melt the ice along its shores.