The biosphere we live in is made up of biomes. A biome is a large geographical region where certain types of plants and animals thrive. Each biome has a unique set of environmental conditions and plants and animals that have adapted to those conditions. The major land biomes have names like tropical rainforest, grasslands, desert, temperate deciduous forest, taiga (also called coniferous or boreal forest), and tundra.
Climate and BiomesThe differences in these biomes can be traced to differences in climate and where they are located in relation to the Equator. Global temperatures vary with the angle at which the sun's rays strike the different parts of the Earth's curved surface. Because the sun's rays hit the Earth at different angles at different latitudes, not all places on Earth receive the same amount of sunlight. These differences in the amount of sunlight cause differences in temperature.
Biomes located in the high latitudes (60° to 90°) farthest from the Equator (taiga and tundra) receive the least amount of sunlight and have lower temperatures. Biomes located at middle latitudes (30° to 60°) between the poles and the Equator (temperate deciduous forest, temperate grasslands and cold deserts) receive more sunlight and have moderate temperatures. At the low latitudes (0° to 23°) of the Tropics the sun's rays strike the Earth most directly. As a result, the biomes located there (tropical rain forest, tropical grassland and the warm desert) receive the most sunlight and have the highest temperatures.
Another notable difference among biomes is the amount of precipitation. In the low latitudes, the air is warm, due to the amount of direct sunlight, and moist, due to evaporation from warm sea waters and ocean currents. Storms produce so much rain that the tropical rain forest receives 200+ inches per year, while the tundra, located at a much higher latitude, is much colder and dryer, and receives just ten inches.
Soil moisture, soil nutrients, and length of growing season also affect what kinds of plants can grow in a place and what kinds of organisms the biome can sustain. Along with temperature and precipitation, these are factors that distinguish one biome from another and influence the dominant types of vegetation and animals that have adapted to a biome's unique characteristics.
As a result, different biomes have different kinds and quantities of plants and animals, which scientists refer to as biodiversity. Biomes with greater kinds or quantities of plants and animals are said to have high biodiversity. Biomes like the temperate deciduous forest and grasslands have better conditions for plant growth. Ideal conditions for biodiversity include moderate to abundant precipitation, sunlight, warmth, nutrient-rich soil, and a long growing season. Because of the greater warmth, sunlight and precipitation in the low latitudes, the tropical rain forest has greater numbers and kinds of plants and animals than any other biome.
Low Biodiversity BiomesBiomes with low precipitation, extreme temperatures, short growing seasons, and poor soil have low biodiversity--fewer kinds or amounts of plants and animals-due to less than ideal growing conditions and harsh, extreme environments. Because desert biomes are inhospitable to most life, plant growth is slow and animal life is limited. Plants there are short and the burrowing, nocturnal animals are small in size. Of the three forest biomes, the taiga has the lowest biodiversity. Cold year-round with harsh winters, the taiga has low animal diversity.
In the tundra, the growing season lasts a mere six to eight weeks, and plants there are few and small. Trees can't grow due to permafrost, where only the top few inches of the ground thaw during the short summer. The grasslands biomes are considered to have more biodiversity, but only grasses, wildflowers, and a few trees have adapted to its strong winds, seasonal droughts, and annual fires. While biomes with low biodiversity tend to be inhospitable to most life, the biome with the highest biodiversity is inhospitable to most human settlement.
A particular biome and its biodiversity have both potential and limitations for human settlement and meeting human needs. Many of the important issues facing modern society are the consequences of the way humans, past and present, use and change biomes and how that has affected the biodiversity in them.