Biomes are large areas of land characterized by their flora, fauna, soil, and climate. These characteristics are heavily influenced by many factors, one major factor being atmospheric circulation, but other factors include the ocean, elevation, and evolutionary history.

Figure 1: The latitude and climate of major biomes

Deserts can be hot, like the Sahara desert, or cold, like the Arctic tundra. Deserts are largely defined by their annual rainfall, or rather their lack of it. Both hot and arctic deserts receive little rainfall but form at different latitudes. Atmospheric circulation plays a major role in this, as deserts form in areas of high air pressure caused by cool, dry, sinking air. As air sinks towards the Earth’s surface it causes strong winds which blow to the west. Due to strong winds, little rainfall, and extreme temperatures, deserts are considered harsh climates resulting in low biodiversity.

Taiga (boreal forests)
Taiga is the largest of the Earth’s biomes and largely forms in the northern hemisphere between 45 to 60° N. In the southern hemisphere, much of this latitudinal range is covered by the ocean. The climate is cold with little rainfall due to its latitudinal position. This biome is largely made up of evergreen trees and lacks biodiversity due to its harsh climate.

Temperate deciduous forests
Similar to Taiga, temperate deciduous forests are largely found in the northern hemisphere. They experience fluctuating air pressure due to being located between high-pressure and low-pressure zones, as well as westerly winds. They receive rainfall throughout most of the year, with some being called temperate rainforests due to the high amount of rainfall they receive. Due to the mild climate and high rainfall, flora and fauna can thrive, resulting in high biodiversity.

Temperate Grasslands
Due to their position in the mid-latitudes, temperate grasslands have a cool climate and receive moderate, seasonal rainfall, with westerly winds. Temperate grasslands receive little rainfall in the warmer months, resulting in few streams, a lack of trees, and low biodiversity.

Savannas are a biome of mixed woodland and grassland, with high biodiversity largely due to their climate. They form between the equator and mid-latitudes, resulting in a hot climate year-round with a wet and dry season. They receive northeast or southeast trades, depending on which hemisphere they are located.

Tropical forests
Tropical forests, such as dry tropical forests or tropical rainforests, form close to the equator. When warm air rises at the equator, a low-pressure region forms causing high humidity and rainfall leading to tropical forests. Dry tropical forests, as their name suggests, do not receive as much rainfall and form further from the equator. The climate is warm and receives a lot of direct sunlight, leading to high biodiversity.