UK
History
UK Squirrel Situation
Most of the England and Wales is now only populated by the Eastern Grey Squirrel (Sciurus Carolinensis), which was brought over from North America from 1876. The original Eurasian Red Squirrel only exists in on a few Islands and the very north of the country naturally, but there are a few other small pockets where it has been reintroduced. Ireland and Scotland have much of the remaining red squirrel population due to them having higher concentrations of replanted pine forest (which the Grey cannot live in) and the reintroduction of the Pine Marten predator (which the Grey cannot easily escape from).
Despite being millions of years old, squirrels likely did not exist here during the ice-age's tree-less tundra (10,000 BC). As the ice receded and trees began to return to the area, squirrels likely came across Doggerland (from what's now mainland Europe), before it was submerged under the North Sea. It is thought that around 3000 BC would have seen the UK's greatest coverage of trees (60-80%) which would have supported tens of millions of red squirrels.
Unfortunately, 3000 BC also saw the ramping up their use of wood (infrastructure, tools, fires) and clearing forests for mass agriculture. Before 1900 the country was almost entirely deforested. Although tree coverage has since recovered to around 10%, the amount of healthy, original woodland is thought to be now less than 1% (according to the Woodland Trust). Squirrels thrive in contiguous forest, and so highly fragmented clusters of poor quality trees don't foster a healthy environment for arboreal animals. If they run out of food they're forced to cross vast swaths of open ground, roads or settlements where their chances of survival plummet. With squirrels gone, the forest's health further reduces, creating a cycle of decline, or even collapse.
When their habitat was almost decimated, squirrels were hunted mostly for their pelts, meat and fur. Later, they were nearly hunted to extinction by landowners, who ironically claim that squirrels destroy trees. Disease ridden Eastern Grey squirrels brought into the country gets the most blame for the red squirrel's decline. However, in reality this is just the latest atrocity that humans have inflicted on them and now this excuse is used to viciously slaughter another innocent animal while claiming moral high ground.
Decades ago, tens of thousands of Red squirrels have been reintroduced into the UK from Scandinavia (to attempt to bolster the numbers). Unfortunately this means that many of the remaining red squirrels in the UK are a different subspecies (Sciurus Vulgaris Vulgaris, rather than Sciurus Vulgaris Leucourus). The native UK red squirrel has a slightly smaller skull and a very blonde tail during the spring moult.
Grey squirrels are an unfortunate reality in the UK, but it's important to remember not to blame innocent animals for the situation. Try not to see them as somehow responsible for the Red squirrel's destruction. That was all human's fault. Grey squirrels are also very sweet creatures. They can be more friendly and thus more photogenic. If you like squirrels and that's all you have, I encourage you to go out and photograph them. I befriended the ones when I was living in Leamington Spa (above) and London.
If you really want to see Red squirrels, and you are living in England, you still have a few options. Brownsea Island (below) and the Isle of Wight in the south have them. Some other small pockets have been reintroduced too. In the north, the Lake District is a good spot, and anywhere further north into Scotland.