Alpine zones

Maria is in Canada, on a trip to hike the Rocky Mountains. The tree cover is thick and dense… but as she hikes higher there are fewer and fewer trees. Instead, the ground becomes rocky, with only small shrubs and grasses. In the distance she can see the snow-capped mountain peaks. Maria has walked into the alpine climate zone.

This climate zone is found on mountains, and in “high lands" — that's where it takes its other names from: it's often called the mountain climate zone or the highland climate zone. What makes this climate zone different from the climate at the bottom of the mountain? One thing you can usually notice on tall mountains is that at some point there are no more trees… Did someone cut them down? Actually, no! They just stop growing!

As you move up a mountain and altitude increases, the temperature becomes very cold — the monthly average temperatures are never over 10 degrees Celsius! Eventually, it gets so cold that trees cannot grow. And so a clear divide forms between where trees are and are not able to grow. This is the tree line, or timberline. It’s also where the alpine zone begins.

The location of the tree line on a mountain varies a lot depending on where you are in the world, what the temperature is, the soil, the amount of rain... The tree line is as low as 650 metres above sea level in Sweden. Meanwhile, on Mount Kilimanjaro in Tanzania, it’s much higher, around 3,950 metres! At the tree line, plant life starts to look more like bushes than trees. Grasses, mosses, and lichens are common.

As you move higher still, these plants get shorter and shorter as they are battered by stronger winds and experience colder temperatures. As you continue to move up, eventually even the smallest plants disappear. At this elevation, there are only rocks and snow throughout the year. The animals that live in the alpine climate zone need to be able to walk on these rocks and survive in cold climates. Mountain goats, with hooves adapted to walking on steep cliffs, are common in the Rocky Mountains.

Canadian lynx have warm coats, and large, wide feet that help them walk quickly on soft snow. People, though, are less likely to live in these climates. It is too cold and windy. As well, at elevations over 750 metres, the air contains much less oxygen than we are used to so it can be difficult to breathe. That is why people who climb mountains often need portable oxygen tanks.

Many characteristics of alpine climates vary according to nearby regions and climates. The alpine climate zone can be found at high elevations on nearly every continent: The Cascades, Sierra Nevadas, and Rockies of North America, the Alps of Europe, the Andes of South America, the Eastern Highlands of Africa, the Himalayas, Tibetan Plateau, Crocker Range, and New Guinea Highlands of Asia. All of these alpine areas tend to be cooler, wetter versions of the climates of nearby areas that are closer to sea level. So although alpine zones share many characteristics, they are not identical. Maria sees a herd of mountain goats in the distance.

Maria’s feet aren’t quite so well adapted to climbing steep cliffs! She’ll be heading back down the mountain now, with lots of great photos of her hike into the alpine zone.