Jens-Christian Svenning (at Aarhus University in Denmark) had some important comments on my last blog post that are worth sharing:
Interestingly, Rhodendron ponticum is not truly biogeographically non-native to NW Europe. It now has a relict distribution in the W Palearctic and was formerly much more widespread. Most notably, it reached the British Isles on its own in the Hoxnian/Holsteinian Interglacial – and guess what – became very abundant. It’s also worth noting that Rhododendron ponticum can be dominant within its current southern range – just as its close relative relative, R. maximum, can be in E North America. So, overall Rp in the UK is not really a truly exotic invader and it’s just behaving normally (given the ideal climatic conditions) (although necessarily benignly from a (local?) biodiversity perspective). In this way it seems more comparable to other native dominating species such as bracken (in the UK).
This longer-term view challenges my notion of what ‘normal’ should be. This invasion will come but it will also go. The Earth’s history is very long, and an interglacial climate excursion or human perturbation are but small things upon it.