Short answers, pulled from the story.
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. There is no universally recognised precise definition, but a common narrower one requires a woody trunk formed by secondary growth that thickens each year.
According to a 2015 estimate, there are about 3.04 trillion trees in the world. Of these, 1.39 trillion are in the tropics or sub-tropics, 0.61 trillion in temperate zones, and 0.74 trillion in coniferous boreal forests.
The tallest known tree is believed to be a coast redwood named Hyperion at Redwood National Park, California, standing 115.85 m tall. The tallest known broad-leaved tree is a mountain ash growing in Tasmania, at 99.8 m.
The earliest trees evolved around 400 million years ago and included tree ferns, horsetails and lycophytes. The first tree may have been Wattieza, whose fossils were found in New York state in 2007, dating to the Middle Devonian about 385 million years ago.
Trees disperse seeds by wind, animals, ballistic ejection and gravity. Birch, ash and maple use winged seeds, the kapok tree uses cottony threads, animals carry seeds in edible fruit or nut caches, and fire triggers seed release in species like the jack pine.
At least 120 drugs come from plant sources, many from tree bark, including quinine from the cinchona tree and Paclitaxel from the Pacific yew. Trees also provide fruits such as apples, dates and olives, cocoa for chocolate, coffee beans, and sap for maple syrup.
About a third of all tree species, some twenty thousand, are included in the IUCN Red List of Threatened Species. Over eight thousand are globally threatened, including at least 1400 classed as critically endangered.