The timescale of change is important to remember. Yes, forests have migrated in the past--but this current trend of climate change is happening so much faster than anything we see in the geological record. They don't have generational timescales to adapt and move this time.
This is a problem that can be solved. We know by the "Chernobyl experience" that nature can return really fast as long as the soil is not reclaimed by man for other uses. We can accelerate that process easily, creating new "highways" for our forests. Most birds don't need it, but big mammals, forest birds and smaller plants and arthropods would benefit a lot of the life-line of having ecological corridors.
I'll drop one of my stupid ideas; what if we start thinking about implement the next level of environmental parks?. The first "nomad national parks" in the planet with gradually movable boundaries designed to minimize the consequences of climate change. Some coastal forests could need a safe exit to move towards the inner land for example. We could change a strip of protected soil with dying trees by some agricultural land in the border of the forest, protect strictly this area and plant there a new extension of the forest. We could include the died wood in the contract to buy a bigger extension in other place and use a mix of native trees (designed to be more resilient against plagues than natural monocultures). The right time to start planning how to do this is forty years ago, but today would be also fine.
