Swanning off earlier than usual

We have seen earlier springs and nesting by birds, with summer migrants now staying the whole year, writes JOHN HOLDEN

THE IRISH climate is the butt of jokes the world over. Rain, rain, rain with intermittent cold summers and inconsistent winters. Irish people complain about the weather almost as much as it rains.

Still, the relatively mild nature of life on an island in the north Atlantic has its advantages. While the plight of the polar bear at the North Pole is well documented, as are effects on crops due to increasing droughts in sub-Saharan Africa, the impact of climate change on Irish plants and wildlife is less apparent.

That doesn’t mean there isn’t a lot of work being done by Irish researchers in this area. In fact, it’s a very heavily researched field, and opinions as to the real effect of climate change – man-made or otherwise – vary.

What’s clear from Irish studies into the local impact of climate change is the effect here is less dramatic than somewhere like the polar ice caps but still very real.

“We’ve been looking at the dates of bud bursts and leafing in trees in spring since the 1960s,” says Dr Alison Donnelly from the School of Natural Sciences at Trinity College Dublin. “Leaves are beginning to appear earlier every year, suggesting it’s getting warmer.”

Phenology, the study of the development of plants and animals, is key to measuring incremental climate-change effects. In any ecosystem, changes in the situation of one species will have a knock-on effect on the next. The arrival time of sub-Saharan spring migrant birds has also changed since the 1980s, says Donnelly. “We found that the main reason for this was the spring temperature. Plus we know that at least one large bird, the whooper swan, that comes in October and leaves in spring, is now departing from Ireland earlier in the season to return to Iceland.”

Donnelly’s research also showed that various moth species were affected.

Not all species respond to warming temperatures at the same rate. This results in “mismatches” in the timing of a predator and prey or a pollinator and plant species, leading to disruption to ecosystem dynamics.

“This will have long-term implications for biodiversity,” says Donnelly. “We’ll have winners and losers but sometimes it’s good to have a mismatch – if you’re the prey, for example. But then if you don’t have enough caterpillars around for the birds in an ecosystem, the bird population will decline.”

These phenological spring changes, measured by Donnelly and her team, are not disputed. And this is not the only area where scientists are recording significant changes in Irish ecosystems. The reason for the changes and how to respond to them, however, are open to debate. “Biological communities are complex,” says Prof Richard Moles, director of the Centre for Environmental Research in UL.

“They change over time as a matter of course. We used to think that ecosystems were in some sense “stable” and therefore, if they showed change, then something must be causing it. Recent research shows that ecosystems are not, and never have been, stable, and must be expected to change over time.

“Ecosystems change for lots of reasons: changes in interaction amongst species, new species arriving, maybe a predator learning new tricks to catch more prey, and also probably completely random events, such as fires.”

Natural or man-made, the question is, should we let these changes in our ecosystem take place or try to force/conserve a different kind of natural order?

“On land we have seen earlier springs and nesting by birds, previously summer migrants staying the whole year around,” says Moles. “But then the last two winters were exceptionally cold, and bird numbers considerably reduced. Woodpeckers are now breeding in Ireland for the first time in a century or more. Is this evidence of climate change, or just the spread of a successful species?

“Should we try to keep ecological communities in our conservation areas “stable” or should we live with the decline of some species and the invasion by others, as maintaining species numbers and niches is what is important, not the species themselves,” says Moles. “This would be a big change in our attitude to conservation. The whole notion of having indigenous species to be preserved, and invasive species to be repelled, would have to be reviewed.”

In 2006, British scientist Dr James Lovelock predicted that by 2040 Britain – and by extension Ireland – would become Europe’s “life raft” as average temperatures in the rest of the continent would have made them uninhabitable. He has since tamed his predictions but his general point about the temperate nature of the Irish and British climate remains true. As dreary as our weather can be, long term it is more than likely an advantage we shouldn’t take for granted.

“The issue in Ireland is that our climate is intermediate: many species are unchallenged by the Irish environment because it is neither too cold, hot nor too dry,” explains Dr Conor Meade of NUI Maynooth. “Our native biota are here as a result of past migration opportunity, and almost any species could survive here given the opportunity. Predicted climate-change scenarios are not that deviant from the present. Thus the overall impact on wildlife may ultimately be minor because climate change will not introduce any great challenges here, in contrast to the Mediterranean, alpine or savannah zones.”

Puffin problem: warmer water could take away food

WHILE THE effects of climate change may appear subtler inland, rising sea levels are a real threat to marine life along Irish coasts. The recording of a 20-metre wave off the coast of Donegal last December – the highest on record off Irish shores – is a dramatic example of how things are changing in the north Atlantic.

This rise in sea level is thought to result largely from an increase in water temperature, which expands when heated. Small increases in temperature therefore cause incremental rises in sea level.

Ongoing studies by collaborative teams from NUI Maynooth, NUI Galway and Galway Mayo Institute of Technology (GMIT) have shown that further changes in the temperature and salt levels of our seas – brought about by climate change – will force species such as cod, salmon and eels into deeper, colder waters. These species will then be replaced by warm water species, such as sea bass and boarfish.

"One thing is clear and that is sea levels are rising, and this affects Ireland as much as anywhere else," says Prof Richard Moles of the University of Limerick. "This will affect shoreline communities of species as there is no place for them to migrate upslope, as their habitat requirements are destroyed by rising water levels. Some marine species, in particular, are very sensitive to water temperature, and there is some support for the view that we are seeing a northward migration of such species, and an invasion of warmer-water species into Irish waters, seaweeds, for example."

This may have knock-on effects, he suggests. Sand eels are considered to be very temperature sensitive and form the major diet of puffins. There may be a problem for puffins if sand eels move too far north for the puffins to reach them. "Sand eels did decline for a few years, but some recent reports suggest their numbers have been restored, so again it is hard to be definitive," said Prof Moles.