There is a notable increase in tree cover in the north east sector of the region, where two factors converge:

First, the proliferation of multiple plantations of Eucaliptus globulus and other subspecies in Guriezo and Castro-Urdiales.
Second, this north-east sector is also the domain of the Holly oak (Quercus ilex) also known as Evergreen or Holm oak, which has experienced a wide expansion, probably because the constant extractions of firewood stalled and started to decrease at some point in time, and perhaps also due to the warmer conditions and the increase of soil dryness due to a certain decrease in rainfall in the last few decades.

Another important idea is a critical advance in the south of the region (mainly in Valderredible). There we see an huge expansion of woodlands of Pyrenean oak (Quercus pyrenaica) and the progression of Scotch pine (Pinus sylvestris) frequently in plantations, some of them abandoned nowadays but in pretty good health. This south part of Cantabria is pretty close to the boundary of the Mediterranean Biogeographical Region, in the transition zone, while the rest of the region belongs to the Athlantic European, Eurosiberian region.

In Liébana (west extreme of the region) a lot of changes can also be seen, especially in the lower part of the valleys, where the temperatures are mild during most of the year. It is also worth noting again that low -and accessible- areas suffered a sustained extraction of firewood during the 40s and 50s, something that can be also applied, up to a point, to the higher parts of the woodlands throughout the entire region.

In general, the lower parts of all the valleys present some kind of increase, probably because in this places the abandonment of the traditional livestock and farming practices has tanken place in a more intense way than in any other part, which creates better conditions for the expansion of the forest.

Along the coast, plantations of Eucaliptus globulus and other subspecies are scattered some kilometers inland. This has been one of the main drivers of the tree expansion in Cantabria, especially since the Sniace Corporation, dedicated to the production of cellulose and rayon, established in Torrelavega back in 1946.