Those farmers cut down the trees in the rain forests because they need to feed their families, that is the truth. If this money from Norway creates sustainable jobs or even provides much needed basic necessities, then the farmers won't be as likely to destroy the rain forests. Norway has taken a wonderful step in the right direction.
Norway's fund to protect the Brazilian rain forests will have some positive impacts. However, more countries need to step up and contribute to this fund as well. Brazilian farmers depend on land cultivation for their livelihood. The world could offer to fund alternatives to cutting down the rain forests to help farmers make a living.
There is no way that Brazilian farmers will use the fund to stop destroying the rain forest, because there is too much benefit from the farmers to use the resources there. There is a concept in economics called the tragedy of the commons. It's hard to put your individual good aside and do what's good for everyone.
Norway's fund to encourage Brazilian farmers to stop destroying rain forest will not have any impact. The reality is that this is just a feel-good measure to make it look like the government is doing something. This is a waste of $400 mn dollars that Norway could have returned to its already overtaxed tax payers.