“Their natural habitat is being destroyed, little by little.”
You're taking a tour of a zoo. You're visiting the gorillas. The tour guide talks about why the number of gorillas in the world is decreasing.
Their natural habitat is being destroyed, little by little.
Use the phrase "little by little" to describe something that happens slowly. Another way to say this is "gradually", but "gradually" is more formal. "Little by little" can be used for both positive and negative things:
We're starting to get the hang of it little by little.
She's losing her memory little by little. Soon we're going to have to move her into a nursing home.
There are actually a lot of phrases like this that express doing something slowly and steadily. Here are a few:
bit by bit
inch by inch
day by day
one by one
An animal species' "natural habitat" is the area and environment that the animal usually lives in. For example, some animals live in rainforests, others live in grassy plains, others live in deep ocean waters, and so on.
These days, a lot of animal species are in danger because humans are destroying the animals' natural habitats. This happens when people build homes and farms, release pollution, and so on.