Resources and environment, Year 10: climate, permafrost and adaptations (Cold environments option)

Permafrost

提示The first part is short for "permanent".

为什么It lies under much of the tundra and can be hundreds of metres deep. It is the thing that sets cold environments apart: it controls the drainage, the soil, the plants and how people can build.

active layer

提示It is the only part where anything happens.

为什么It may be only a few centimetres to a metre or so deep. All plant roots and all soil life are confined to it. A warmer climate makes it deeper each summer.

The frozen permafrost below will not let it soak down

提示Think what lies under the thawed surface.

为什么Frozen ground is waterproof. Evaporation is also slow because it is cold. So the little water there is stays at the surface, which is why the tundra has so many pools, and so many insects, in summer.

Tundra

提示The other one is ice sheet and almost bare.

为什么Polar areas stay below freezing nearly all year and are mostly covered by ice. Tundra lies on their warmer edge. It has a growing season of about 50 to 60 days, when the surface thaws.

precipitation

提示The general word for rain, snow, sleet and hail.

为什么Very cold air holds little water vapour, so little snow can fall. Tundra gets about 150 to 250 mm a year and the polar ice sheets even less. The snow that does fall hardly melts, so it builds up over thousands of years.

The cold makes decomposition very slow, so dead plants release their nutrients slowly

提示Bacteria and fungi barely work in a freezer.

为什么Dead plant material piles up as peat faster than it rots. The nutrients stay locked inside it. With few nutrients and a short summer, plants grow slowly, which in turn limits the animals.

To stay out of the wind and keep in warmth

提示Crouch behind a wall on a freezing, blowy day.

为什么The air right at ground level is calmer and a few degrees warmer. In winter a low plant is also covered and insulated by snow. A tall plant would be dried out and damaged by wind carrying ice.

Roots can grow only in the thin layer that thaws above the permafrost

提示Half a metre down, the ground is like concrete.

为什么Roots cannot push into frozen ground or take water from it. This is also why there are no tall trees: a tree needs deep roots to hold it up.

blubber

提示It rhymes with rubber.

为什么Fat is a poor conductor of heat, so it insulates the animal in icy water, where fur alone works less well. It is also a store of energy for times when food is scarce.

It camouflages them against the snow

提示Hard to spot, whether hunting or hiding.

为什么The hare is harder for predators to see and the fox can get closer to its prey. In summer the fox turns brown or grey to match the bare ground, and so do hares in the southern part of their range. The winter coat is also thicker.

migrating

提示A regular seasonal journey.

为什么They return in summer to feed on the short burst of plant growth and insects. Other animals stay and cope in a different way, by hibernating or by living under the snow.

With so few species, each animal depends on only one or two others for food

提示Remove a link when there are hardly any spares.

为什么In a rainforest a predator that loses one kind of prey can switch to another. In the tundra there may be no alternative. So a change to one species, from disease, hunting or a warming climate, passes quickly through the whole ecosystem.