I'd say there isn't a difference in the meaning but what you emphasize is obviously different when you change the word order. "It is useful to plant trees." Here's the emphasis is on the adjective "useful" "Planting trees is useful." Here you emphasize the action instead.

There is no difference in meaning.

Arwa: What you are seeing is the flexibility of the English language. As you can see, the word order is itself very flexible.

they're are equals, same meaning. u just change the order

1st sentence = how? 2nd sentence = what?