Um, you do know that forests have stages? Right?

Evergreens tend to be one of the first stages. Evergreens generally grow quickly and tolerate fairly crappy soils. "waterlogged soil with high clay content" (from the article) is a REALLY crappy soil for trees. The littering of needles generally helps add some level of nutrients back to depleted soils (an acidic humus is going to be vastly better than completely leached out waterlogged clay) It's why you plant evergreens on strip mined areas to help reclaim them.

After the evergreens, the deciduous trees start coming in from the edges--but this takes decades.

Now, it's possible that Ireland/Scotland don't have enough deciduous trees (or, in the case of Scotland, the climate may simply not be correct--Scotland has a lot of land that's really crappy for growing anything much at all) to start the process and those trees need to be added to their planning. Fair enough.

However, I don't see any discussion or acknowledgement of any of this in the article.