Two numbers, temperature and rain, predict what landscape will grow: rain against the air’s thirst, the growing season trees need, and a mountain climb that passes through every biome in a few thousand metres.
Step 1 of 6 · Same rain, different land
Step 1 of 6
Same rain, different land
A biome is a large region known by the shape of its plants: tundra, taiga, temperate forest, grassland, desert, savanna and tropical rainforest. Biomes are named for their plants because a plant cannot run from bad weather, so it is the clearest record of the climate. The chart beside the Scene places the biomes by just two numbers, the mean yearly temperature and the yearly rainfall, and the climate you chose is the blue dot.
Rainfall per year is locked at 500 mm, dry, and Mean temperature is at Boreal: a conifer forest.
Step 2 of 6
Rain against thirst
Rain is only half of the water budget. The other half is how much water the air takes back from the soil and leaves: the potential evapotranspiration. Warm air holds about twice as much water vapour for every 10 °C, so a warm place is thirsty. What decides is the moisture ratio:
where is the yearly rain and the potential evapotranspiration, both in millimetres.
Below about the land is desert. Between and there is water enough for grass but not for a closed forest: grassland. Above trees close a canopy. The bars under the chart show the rain in blue and the thirst in orange.
Step 3 of 6
Enough for a rainforest
The tropics have no winter, and trees grow all year, so they need water all year: a rainforest needs a moisture ratio of at least . Below that, grass fills the gaps between the trees: savanna.
Step 4 of 6
The cold edge
The cold end of the chart has a different limit. Trees need a growing season warm enough and long enough: if its mean is below about 6.4 °C, or it is shorter than about three months, trees do not grow. Mean temperature is locked at Arctic.
Step 5 of 6
Up a mountain
Air cools by about 6.5 °C for every 1,000 m of height, so a mountain is a shortcut through the biomes: a climb of a few thousand metres in the tropics changes the climate like a journey of thousands of kilometres towards a pole. The rain on the slope stays the same rain; only the temperature falls. Raise a mountain will lift the tile into a mountain 5,000 m high.
Step 6 of 6
Biome and habitat
A habitat is smaller and more particular than a biome: the place where one kind of living thing lives and finds what it needs. Each biome in the Scene has two typical animals, and each has its own habitat within the biome.
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Each step sets up the Scene for you, and a control marked “fixed” stays put for that step.
Practice · Predict, then look
500 mm a year at Boreal grows a conifer forest. Predict what grows on the same rain when Mean temperature rises to Tropical.
Practice · Predict, then look
500 mm a year at Boreal grows a conifer forest. Predict what grows on the same rain when Mean temperature rises to Tropical.
Practice · Calculate
Somewhere temperate, with a mean of 12 °C, the air could take back about 618 mm a year, and the rain is 500 mm. What is the moisture ratio?
Practice · Calculate
Somewhere temperate, with a mean of 12 °C, the air could take back about 618 mm a year, and the rain is 500 mm. What is the moisture ratio?
Practice · Reach the target
Mean temperature is locked at Tropical. Find the smallest Rainfall per year at which a rainforest grows, and press Check.
Practice · Reach the target
Mean temperature is locked at Tropical. Find the smallest Rainfall per year at which a rainforest grows, and press Check.
Practice · Predict, then look
At Arctic, with 1,000 mm a year, there is treeless tundra. Predict what happens when Rainfall per year rises to 3,000 mm.
Practice · Predict, then look
At Arctic, with 1,000 mm a year, there is treeless tundra. Predict what happens when Rainfall per year rises to 3,000 mm.
Practice · Predict, then look
At the foot there is dry savanna, 500 mm a year in the tropics. Predict what grows on the slopes when you choose Mountain under Raise a mountain.
Practice · Predict, then look
At the foot there is dry savanna, 500 mm a year in the tropics. Predict what grows on the slopes when you choose Mountain under Raise a mountain.
Practice · Choose
In a European temperate forest live a woodpecker, which lives in tree trunks, and a woodlouse, which lives under a rotting log on the ground. What do they share?
Practice · Choose
In a European temperate forest live a woodpecker, which lives in tree trunks, and a woodlouse, which lives under a rotting log on the ground. What do they share?
Lesson complete. Every practice question here is done.