Biomes and What Draws Their Boundaries
Vegetation across the world falls into a modest number of types, and where each one occurs is predicted well by temperature and rainfall alone. The exceptions are as informative as the rule, because they point at fire, grazing or soil doing the work instead of climate.
What a learner can do afterwards
- Place a biome on a temperature and precipitation plot and justify the position
- Explain why unrelated plants in the same biome converge on the same growth form
- Give a case where the biome present is not the one climate predicts, and name the cause
1 · Read
World vegetation sorts into a few biomes, and temperature plus rainfall place most of them. Warm and wet grows evergreen rainforest, where trees stay green and tall all year. Cold or dry corners grow their own matching forms, and the plot of rain against heat predicts which.
Plants in one biome converge on shared answers. Desert dwellers store water or drop leaves to outlast long dry spells, whatever their ancestry. The same pressures pick the same growth forms again and again.
The rule has famous exceptions that prove the pressures. Fire and grazing can hold open grassland where rain could raise trees, and thin or salty soil can bar the forest the climate invites. Ecologists track moss campion survival, growth, and reproduction across latitudes to test whether it still holds its range as the climate warms. Warming now drags the temperature and rainfall zones across the map, so species must move with them, adapt, or disappear.
Planting trees is no simple climate fix: each biome stores carbon and steers water its own way. Guarding the biomes we hold matters as much as planting new ones.
Climate draws most biome borders, exceptions name the other authors, and shifting zones move the map.
2 · Watch
Take it off screen
Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.