"If you have faith as small as a mustard seed, you can say to this mulberry tree, 'Be uprooted and planted in the sea,' and it will obey you".
There is a problem here, Have you ever found someone with a small faith large enough to move grown trees around at will? Are there tree movers? Are there people with faith as small as a mustard seed?
It may be there is no one with a faith as large as a small mustard seed. Or maybe we have not looked in the right place. Trees are being moved, we just haven't been watching. Or then again, maybe such faith only works on more important things: like raising the dead, healings, success in business, passing exams........ life in all its fullness type things.
Setting aside the improbable possibility that Jesus had psychotic anti-environmental delusions, we must ask, what is this tree moving faith? It could be a powerful psychic determination, a total concentration without doubt or waver. If its application works, then we obviously have it. If it doesn't work, then we obviously didn't have enough of it. Actually it's better to blame everyone else and say they didn't have enough of it and that's why my faith didn't work.
There are many people who think they only need to ask God for something with total certainty and they will get it. And why? Because you only need faith as small as a mustard seed to move that proverbial tree. When their prayer doesn't work out, they conclude that they didn't have enough faith.
So what's the problem? It all stems from a failure to read the Bible properly. Consider what Jesus actually said. "If your brother sins, rebuke him, and if he repents, forgive him". The disciples were no fools. This command of Jesus was going to be a hard one to follow. So one of them responded by saying, "Increase our faith". Jesus then said those famous words. The point is simple enough. What Jesus commands can be done if we take him at his word - if we trust him, if we have faith. Even the smallest most ineffective trust in the commands and promises of Jesus will result in the commands and promises being achieved. Jesus was simply saying something like this, "Boys, It's not easy to forgive someone who has hurt you, but if they ask for your forgiveness, forgive them. And remember this, you can forgive them, for whatever I tell you to do can be done, even by someone whose dependence on me is as weak as a politician's logic".