Forests cover almost a third of the Earth's land.
They are home to 70% of Earth's land animals and plants.
But these habitats are disappearing, fast, in a process called deforestation.
Trees are felled for fuel and to make products like furniture and paper.
While farmers burn forests to clear land for crops and cattle, destroying these valuable natural habitats.
Forests felled for:
Materials for industry
Land for agriculture
Tropical rainforests are especially important. They are home to more than half of all plant and animal species on Earth.
But it's thought that deforestation is causing over 50 species to become extinct every day, as their natural habitat is destroyed.
Plants, which could be used in medicine, are killed before they're even discovered.
But it's not just the immediate destruction of wildlife that's the problem.
Trees maintain the right conditions for all other life on Earth.
They affect the soil, atmosphere and climate of the whole planet.
Without roots to hold the soil together, the ground is more likely to collapse in a landslide, or be washed away by flooding.
Trees also pump water into our atmosphere, through a process called transpiration.
Without them the environment becomes dry.
With fewer leaves falling and decomposing, soil loses up to 90% of its nutrients.
Trees absorb a greenhouse gas called carbon dioxide and give out oxygen.
Rainforests produce 40% of the world's atmospheric oxygen.
Trees vital for life on Earth:
Create fertile, moist and stable soil
Release water through transpiration
Absorb carbon dioxide and release oxygen
But when they're burned, they release carbon dioxide instead.
Around half of the Earth's forests have already disappeared.
With 2000 trees destroyed every minute, deforestation now accounts for a quarter of greenhouse gas emissions.
And in just 100 years, there may be no rainforests left at all.
We'll never stop forests being cut down, but we can make it more sustainable.
Replacing felled trees will protect the ecological balance of the whole planet.