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Examining how human activities like farming and building change the Earth's biomes.
Imagine a forest where the trees are like giant apartment buildings for millions of animals. What happens to the 'tenants' when their buildings are suddenly taken away to make room for a farm?
When humans cut down large areas of forests to make room for farms, roads, or buildings, it is called deforestation. In the rainforest, trees are not just plants; they are homes. Many animals, like monkeys and sloths, spend their entire lives in the canopy (the top layer of trees). When these trees are removed, animals lose their food, their shelter, and their protection from predators. Without trees, the soil also washes away more easily, making it hard for new plants to grow. This changes the biome from a lush forest into a dry, open space where rainforest animals cannot survive.
1. A Toucan lives in a hollow tree and eats fruit from nearby branches. 2. Humans cut down a -acre patch of forest to plant soy crops. 3. The Toucan's home is gone, and its food source is replaced by a plant it cannot eat. 4. The Toucan must fly a long distance to find a new home, but other areas are already full of other birds.
Quick Check
What is the term for clearing away large numbers of trees to make room for human activities?
Answer
Deforestation
Every animal needs a specific environment to survive, which we call a habitat. When humans build cities or large farms, they cause habitat loss. This is the number one reason animals become endangered. An endangered species is one that is at risk of disappearing from Earth forever (extinction). If a forest is cut into small 'islands' of trees, animals become trapped. They might not find enough mates to have babies, or they might not find enough food. For example, if a tiger needs square miles to hunt but only has left, it cannot survive.
Imagine a grassland biome where prairie dogs live. 1. A new housing development is built, covering of the land with concrete. 2. The available habitat shrinks from units of space to only units. 3. The prairie dogs become crowded, food runs out, and predators find them more easily because they have fewer places to hide.
Quick Check
Why does habitat loss lead to a species becoming endangered?
Answer
Because the animals lose the specific food, shelter, and space they need to survive and raise their young.
Sometimes humans don't remove a biome, but they change it by adding harmful things called pollution. When farmers use strong chemicals to kill bugs, or factories dump waste into rivers, those toxins enter the food chain. This process is dangerous because the toxins don't go away; they move from one animal to the next. A tiny insect eats a bit of poison, a fish eats insects, and a large bird eats fish. By the time the poison reaches the top of the food chain, it has built up to a very high, dangerous level.
Let's look at how toxins multiply as they move up: 1. Each tiny water plant absorbs unit of pollution. 2. A small fish eats plants, so it now has units of pollution. 3. A large fish eats small fish. It now has units of pollution. 4. An eagle eats large fish. The eagle ends up with units of pollution! This can make the eagle's eggs too thin to hatch.
Which human activity is most likely to cause deforestation?
If a species is 'endangered,' what does that mean?
Pollution becomes less dangerous as it moves from small animals to large animals in a food chain.
Review Tomorrow
In 24 hours, try to explain to a friend or family member how a chemical sprayed on a leaf could end up hurting a hawk at the top of the food chain.
Practice Activity
Look around your neighborhood. Can you find one example of habitat loss (like a new building) and one way humans are trying to help (like a park or birdhouse)?