Monday 18 December 2017

Flora fooled into thinking that spring has sprung

Climate change is confusing our flowers

Niamh Donohoe, a gardener at the National Botanic Gardens in Glasnevein, with a clematis blooming out of season. Photo: Tony Gavin
Niamh Donohoe, a gardener at the National Botanic Gardens in Glasnevein, with a clematis blooming out of season. Photo: Tony Gavin
Mark O'Regan

Mark O'Regan

The mild winter weather has created confusion in some of our flower family - with certain species blooming up to three weeks early.

And the relentless march of climate change is causing trees to produce leaves out of season.

Increasingly erratic weather patterns are causing climate zones to shift 50cm northwards every hour.

While the bright colours of early spring will be a welcome sight for some, experts have warned they point to the damage climate change is having on our ecosystem.

Dr Matthew Jebb, director of the National Botanic Gardens in Glasnevein, Dublin, said the regularity of wildly fluctuating weather is becoming more acute with each passing year.

He pointed out that daffodils were in bloom in the National Botanic Gardens last December - but this year they are nowhere to be seen.

"Each year different plants seem to do different things," he said.

"One of the great lessons of climate change is that some events are very unexpected.

"Sometimes we have a fairly cool winter - and yet surprisingly things come into bloom. This year we had an incredibly warm autumn all the way up to Christmas, and quite a few spring flowers are out. What's interesting at the moment is how unexpectedly various trees and shrubs are performing."

Since the late 1960s, experts at the National Botanic Gardens have been measuring the dates of flowering and leaf fall of 30 species of plants.

"These are the same plants that are being distributed across Europe by Humboldt University in Germany," Dr Jebb said.

"We have to remember that 50 years ago the phrase climate change hadn't been invented - but thankfully we now have relevant data that is just remarkable."

He said the data showed that a lot of trees and shrubs in Ireland were flowering and producing their leaves two to three weeks earlier than was the case in the 1970s. "This shows the significance of slowly rising global temperatures," said Dr Jebb. "It also reveals that the climatic zones in Europe are shifting northwards.

"Spring is coming earlier to northern Europe than it used to in the past. The zones are shifting northwards at about 4km per year. That is 12 metres a day, or 50cm an hour."-

He said that once people see at first-hand the effect of the changing climate on plants, they get an extremely accurate reading of what is happening in the world.

"Climate change is real; there's no doubt about that," he said. "The debate remains as to whether humanity is responsible. However, most scientists argue the circumstantial evidence suggests that is the case."

Speaking to the Sunday Independent, he pointed out the iris, among the most elegant of spring flowers, had already started to flower this month. "Normally an iris would be in bloom in May and June, but we have had some flowering in December," he said.

"They went through a cool September and then October and November were very warm, we also had gentle rainfall. They assumed they had come into spring, so they were tricked into flowering ahead of a true spring."

Verbascum, he said, was yet another example of how unusual weather patterns were upsetting the natural order of the seasons.

"The cool September had tricked them into thinking winter had come and gone," Dr Jebb said. "By November, it had started to shoot, thinking it was springtime."

Fifty years ago, he added, it was also extremely difficult to successfully grow foliage from South Africa and the Mediterranean in Ireland.

"They needed a lot of mollycoddling and protection - but now we find a huge number of these semi-tropical plants are quite happy flowering and growing out of doors," he said.

"All the signs are this kind of unusual growth pattern will become even more prevalent in the future."

Ever-changing weather patterns will continue to confuse our plant and flower life, he concluded.

Sunday Independent

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