5 TOP RESONS WHY:

1. They help us breathe. Forests pump out oxygen we need to live and absorb the carbon dioxide we exhale (or emit). A single mature, leafy tree is estimated to produce a day's supply of oxygen for anywhere from two to 10 people. Phytoplankton is more prolific, providing half of Earth's oxygen, but forests are still a key source of quality air.

2. They're more than just trees. Nearly half of all known species live in forests, including 80 percent of biodiversity on land. That variety is especially rich in tropical rainforests, from rare parrots to endangered apes, but forests teem with life around the planet: Bugs and worms work nutrients into the soil, bees and birds spread pollen and seeds, and keystone species like wolves and big cats keep hungry herbivores in check.

3. They keep Earth cool. Trees also have another way to beat the heat: absorb CO2 that fuels global warming. Plants always need some CO2 for photosynthesis, but Earth's air is now so thick with extra emissions that forests fight global warming just by breathing. CO2 is stored in wood, leaves, and soil, often for centuries.

4. They help us explore and relax. Our innate attraction to forests, part of a phenomenon known as "biophilia," is still in the relatively early stages of scientific explanation. We know biophilia draws humans to water, woods and other natural scenery, though, and exposure to forests has been shown to boost creativity, suppress ADHD, speed up recovery, and encourage meditation and mindfulness. It may even help us live longer. Forest is important for us to form many reasons and it has several values to us.

5. They help us make things. Where would humans be without timber and resin? We've long used these renewable resources to make everything from paper and furniture to homes and clothing, but we also have a history of getting carried away, leading to overuse and deforestation. Thanks to the growth of tree farming and sustainable forestry, though, it's becoming easier to find responsibly sourced tree products.