3billion trees sounds like a lot, but the area it takes to plant those trees is less the 1/1000 of the area of the EU. I highly doubt, that this would lead to a measurable decline in EU farm land and especially high quality farm land.
An analysis of the policy documents outlining the practical measures of the Green Deal shows that it will decrease carbon emissions in Europe, but also increase carbon emissions outside the EU. This increase is more than double the amount of carbon emissions saved by the Green Deal.
Their conclusion is that the Green Deal in its current form will lead to an increase of 244.8% in emissions in countries outside the EU compared to the Green Deal's carbon reduction goal in the land, land use change, and forestry sector within EU borders.
Yes the idea is that other countries will follow suit, but who's gonna ask countries that are still developing to pay extra 25% cost of something that's sustainable.
This is only about land, land use and forestry. So the request is pretty much not to cut down forests. That is asked all the time, for very good reasons.
Discussion of climate, how it is changing, activism around that, the politics, and the energy systems change we need in order to stabilize things.
As a starting point, the burning of fossil fuels, and to a lesser extent deforestation and release of methane are responsible for the warming in recent decades:
How much each change to the atmosphere has warmed the world:
Recommended actions to cut greenhouse gas emissions in the near future:
Anti-science, inactivism, and unsupported conspiracy theories are not ok here.