I FEEL I must reply to Mark Smith's column on floral invaders ("Weeding out hysteria about floral invaders", The Herald, July 21).

The invasive rhododendron Ponticum is actually a human-created hybrid that does not occur in nature, specially selected by horticultural­ists in the 1800s to be hardy. Interestingly, there was a news story recently about a couple of hillwalkers who got lost in a large rhododendron forest on a mountainside in Ireland and had to be rescued by the mountain rescue team: a glimpse into the future?

Mr Smith raises valid points in relation to our inconsistencies in how we treat different invasive species and the difficulties of prioritising control, but this does not mean that some species do not do real ecological damage; and by no means do all introduced species eventually stabilise in harmony with native species. The World Conservation Union, IUCN, states: "They represent the second most significant cause of species extinction worldwide after habitat destruction, and in islands, they are indisputably first." And one also has to be careful with the use of words: of course their presence can increase the diversity of species present (but can also reduce it) but increasing diversity is not the same as conserving global biodiversity. In the long term, the spread of introduced species can result in regional ecological homogeneity owing the dominance of successful invaders - the opposite of a varied biodiversity.

The fact that the concept of invasive species "is a modern idea" to me seems largely irrelevant. After all, the term ecology was only created in 1866: does this invalidate the science of ecology? And does Mr Smith decry archaeology as well, which is about trying to conserve our cultural heritage, in addition to an ecological approach that is trying to conserve our natural heritage?

Dr James Fenton,

Polldoran, Clachan Seil, Oban.