Similar to the achievement “Home Wrecker” except with trees.
Trees can be easily destroyed on foot by using your knife to attack them, using explosives at their base, or just shooting them a lot.
In vehicles you can crush trees by driving over them, shooting them, or causing your vehicle to blow up near them.
If you’re having trouble with this achievement I recommend loading up the level “Air Force One” and then simply using the rockets to destroy many trees at a time. Fire down into large forests and you’ll have hundreds of trees on the ground in a split second.