Why are trees resources scarce?

Energy resources are basically:

* Coal (not scarce. There's still plenty of coal. The only problem is it releases carbon that has been buried for millions of years, adding it to the greenhouse layer)

* Oil (beginning to run out. Many scientists think that "Peak Oil" [when it was plentiful] has already passed us by. Oil, like coal, also releases carbon. The world relies on oil to run transportation, so we need to find other ways quickly)

* Natural gas (I think it's like oil, getting scarce. It also releases carbon.)

* Uranium (not scarce. Good for producing fairly clean electricity, but it is dangerous and leaves residue that's very difficult to store safely. Occasionally has nuclear "accidents", the worst of which was Chernobyl.)

* Solar Power (scarce because we have only recently realised its value. Scientists and inventors are desperately trying to get it going and fast.)

* Wind Power (scarce. Same as Solar Power. Good as a second string for windy countries.)

* Hydro-Power (Some countries have lots [70% of New Zealand's electricity comes from water]. Big dams are difficult and expensive, but good when they are running, so long as the rain keeps falling. Inventors are working hard at Tidal and Ocean Wave experiments, hoping for good news!)

* Geothermal Power (scarce. Same reason as Solar Power. Lots of potential for some countries.)