Many people have asked me to explain exactly what pruning is. Since we’ve just celebrated earth day, it’s important to speak up on a tree’s behalf.
Pruning is cutting branches or parts of trees or for improving the shape or growth of trees (using shears, pruning saws, chainsaws). It’s the most common tree maintenance procedure. Usually, trees are pruned as a preventative or corrective measure to remove dead branches, crowded or rubbing limbs, to eliminate hazards, and to increase light and air penetration. No branch should be removed without any reason--each cut to a tree has the potential to change the growth.
Trees in national parks don’t usually require human intervention because they are natural spaces and should be left to their own devices. But when humans and trees share space, it’s a different dynamic. Small trees will eventually grow to be big trees, and sometimes they grow in places that are inconvenient or even dangerous (over buildings and wires). It’s best to prune trees when they are young; they’ll require less corrective pruning as they mature. Also, small cuts do less damage than large cuts--if you proactively maintain young trees with pruning, you’ll reduce the need for more drastic pruning later.
Here's a link to proper pruning techniques
If we think ahead and care for trees properly, we can avoid instances where hazardous trees need to be removed completely.