Water and Biomes

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Regional differences in climate and the hydrological cycle greatly determine the quality and variety of organisms in a particular place. Due in part to the regular distribution of rainwater on the Earth’s landmasses, large regional ecosystems called biomes have evolved over time. Biomes are characterized by their amount of annual rainfall, mean annual temperature, and major types of vegetation. You will recall the discussion of biomes when you studied biodiversity in Chapter 1.

Figure 10: Biomes of the World1

In Figure 10, the dark green regions along the equator indicate the world’s tropical rainforest biome, while the intermediate blue shaded regions at around 60°N indicate the taiga, or northern coniferous forest biome. Both biomes receive enough water to support trees, but the tropical rain forests enjoy warm weather year around, while the taiga has a long cold winter, which reduces total plant growth and biodiversity. The dark and light shades of salmon indicate dry and desert regions with too little water to support large plants like trees. The brown color indicates more sparsely vegetated regions including shrub land, grassland, savannas.

Questions to Consider

  • Imagine if the entire area of the amazon rainforest (5.5 million square kilometers) was deforested. What effect would this have on the hydrologic cycle?
  • What physical factors govern the cycling of Earth’s water?