Exotic species are increasing in Ireland, and feeling too much at home, botanist Matthew Jebb tells Shane Hegarty.
'We often get mild winters and the plants are well adapted to that," explains Matthew Jebb, the keeper of the herbarium at the National Botanical Gardens, "but there is no doubt that a large number of trees and spring flowers are leafing and flowering a lot earlier than they used to. Over the past 50 years we can say that snowdrops are flowering 10-12 days earlier. Oak trees leaf 10 days earlier. I've been told that apple blossom buds have shown on some trees, and hopefully the expected cold weather will hold them back. An exceptionally late frost can destroy an entire apple crop.
"For the past 40 years we've been measuring 18 trees, their date of bud burst, flowering and leaf fall. It's Europe-wide and uses clones, so that the same redcurrant is grown in Finland, Ireland, Spain and Greece. It has given us a great span, and the evidence gained has shown a huge shift. The growing season is longer in the redcurrant by 10 days, although it can vary. Poplar trees are 20 days shorter than in the 1980s.
"There are many things we used to grow in hothouses that we now grow outdoors, although that's partly due to trial and error and technique. We now have 20 species of palms growing outdoors.Certainly, these kind of plants are blossoming better than ever and are exceptionally happy. But that's what 10 hot years in a row will do.
"Autumn is also much longer, and plants have a chance to build up food reserves. Maize needs 120 sunny days to flower, and was traditionally grown here only for silage, but now we can get a big crop of corn.
"While pleasurable in a way, it's also of great concern. Some [ plants] might be too much at home. Achill is overrun by gunnera - which looks something like spiny rhubarb - which is devastating bogs and is really difficult to eradicate. What has happened, to my mind, is that our native flora and fauna have never been so depleted and fragmented. New plants coming here find it wonderful and they've left behind pests and predators.
"There are others on the way. Hundreds of thousands of pots are imported into Ireland each year and they can bring pests. The vine weevil is now at home in Ireland. The processionary moth, which eats oak and is incredibly toxic, is now in south-east England and undoubtedly on its way here. We're laying ourselves open to the equivalent of Dutch elm disease again, and the climate change is definitely contributing, especially when the native eco-system is in rag order.
"It's a global phenomenon. Africa is always on the cusp of being too arid for the human population. If climate change increases, the impact on the remaining forests is likely to increase. Africa's prospects from global warming are truly horrific."