My Science School

CLIMATE ZONES

Variations in the intensity of sunlight striking different parts of Earth drive global air movements and weather systems. Between them, these influences create a variety of climate zones, ranging from steamy tropical rainforests to the icy deserts of Antarctica. Most of these climate zones have a distinctive type of vegetation, which is the basis of a whole wildlife community, or biome.

• TROPICAL RAINFOREST

Intense sunshine near the Equator makes moisture evaporate and rise into the air to form huge storm clouds. These spill heavy, warm rain on the land below, fuelling the growth of dense rainforests.

• TEMPERATE FOREST

Temperate climates are neither very hot nor very cold. Near oceans, the mild, damp weather allows trees to grow well in summer, but many lose their leaves and stop growing in winter.

• POLAR AND TUNDRA

The Polar Regions get only weak sunlight in summer, and are dark all winter. They stay frozen all year, but in the north this icy region is surrounded by tundra, which thaws in summer allowing some plants to grow.

• MOUNTAIN

High mountain peaks are very cold, like Arctic tundra, and they have similar tough, low-growing vegetation. Lower mountain slopes are warmer, allowing trees to grow. The upper edge of this zone is called the tree line.

• DESERT

Some regions get so little rain that they are deserts. Many lie in a zone of hot, dry air near the tropics, but others are just too far from oceans. Some plants live in deserts, so they are not quite barren.

• MEDITERRANEAN

The dry shrublands that lie between the temperate zones and the main desert regions are named after the Mediterranean area where they are most common. The tough-leaved plants that live there can survive drying out in the hot summers.

• CLIMATE ZONES

The climate zones of the world form bands, with tropical rainforest near the Equator, most deserts in the subtropics, and boreal forest in the far north. Grasslands develop where it is too dry for trees.

• TROPICAL GRASSLAND

Tropical regions that are not within the zone of heavy rainfall are too hot and dry to support dense forest. They are seas of grass, often known as savannas, sometimes dotted with trees that can withstand long droughts.

• TEMPERATE GRASSLAND

Some temperate areas get little rainfall, usually because they lie at the hearts of great continents. Too dry for trees, they are naturally grassy steppes and prairies – although many are now farmland.

• BOREAL FOREST

To the south of the Arctic tundra, the northern continents support a band of dense forest. Most of the trees are conifers with stiff needle-like leaves that can survive the long, freezing winters.

Picture Credit : Google

In our fight against global warming and climate change, trees are considered part of the solution. But emerging research suggests that trees are also part of the problem.

Trees are carbon sinks locking up vast amounts of carbon dioxide from the atmosphere. This way, they help protect the planet from the harmful effects of the greenhouse gas. But there seems to be another face to trees, that scientists have uncovered only recently. They find that trees emit methane, which is a greenhouse gas 45 times more potent than carbon dioxide at warming our planet. Scientists unofficially call this treethane (tree methane). However, it's currently unknown just how much of methane is emitted by trees.

Emission of methane from cottonwood trees was first observed in 1907, but the finding was reported mainly as a novelty and was largely ignored. Subsequent research has picked up only recently, but in a big way. An expanding network of researchers has discovered methane release from trees from the vast flooded forests of the Amazon basin to Bomeo's soggy peatlands, from temperate upland woods in Maryland and Hungary to forested mountain slopes in China.

Source of methane

Some lowland forest trees such as cottonwood emit flammable methane directly from their stems, which is likely produced by microbes living within. Scientists think trees may also be emitting methane from a direct photochemical reaction thought to be driven by the ultraviolet wavelengths in sunlight Research in this area is still in its early stages and so there is a lot left to be understood.

But understanding why, how and which trees emit the most methane is crucial, as trillions of trees are being planted across the world in an effort to mitigate climate change. However, scientists point out that the amount of methane emitted by trees is generally dwarfed by the amount of carbon dioxide they take in over their lifetime. Forests are still key to maintaining a safe climate, they point out.

Picture Credit : Google