Out of season
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Climate change has repeatedly been identified as one of the greatest challenges faced by humanity, but our wildlife too will have to cope with a changing environment.
Many species have the capacity to adjust to climate change, by modifying their behaviour or moving north as temperatures rise.
The exact effects of climate change are notoriously difficult to predict, making its consequences for wildlife equally hard to measure. “In terms of biodiversity, one of the major difficulties is how we plan and target action for uncertainty,” says Nick Collinson, Head of conservation policy at the Woodland Trust.
This was however the goal of the MONARCH (Modelling Natural Resource Responses to Climate change) programme, funded by a coalition of major UK conservation organisations. The project studied 32 of Britain’s endangered species, identifying climate change ‘winners and losers’ according to their ability to adapt. Some species seemed set to gain from climate change, but for others the future looks gloomy.
A question of timing
Climate change is having a major impact on our seasons, and in the same as we discard our winter coats to welcome an early spring, wildlife too reacts to changes in season.
The first four months of 2007 were the warmest since records began in the 17th centuryPhenology is the study of the timing of recurring natural phenomena such as the flowering of plants or the hatching of birds’ eggs. These timings vary as wildlife react to subtle cues from their environment. “In the spring, plants and animals respond to two different things: one is increases in day length and the other increasing temperature,” says Collinson.
But whilst variations in day length follow a regular pattern year after year, climate change is affecting temperatures throughout the year.
In the UK, the first four months of 2007 were the warmest since records began in the 17th century, paving the way for our earliest spring yet. Plants flowered on average two weeks early, frogspawn was being observed at Christmas, and insects emerged a whole three weeks earlier than the norm.
Phenology was originally used essentially for agricultural purposes, but nowadays it has become a useful means of monitoring the effects of climate change.
In Britain today, 50,000 people contribute to the UK phenology network’s records of the changing seasons, supported by the Woodland Trust and made popular with the BBC’s Springwatch and Autumnwatch TV programmes.
Out of sync
Animals and plants are not all equal when it comes to adapting to a new climate. “Different taxonomic groups are responding at different rates to the same changes in temperature,” says Collinson.
One of the consequences of species’ varying capacity for change is a loss of synchronicity within food webs. An example of this is the interaction between oak trees, oak winter moths and great tits.
The great tits’ eggs hatch at the same time as moth larvae emerge, themselves timed to coincide with the sprouting of young, tender oak leaves. In this way, juvenile moths and birds are both guaranteed a plentiful supply of food – but this may be changing.
“What the evidence suggests is that the winter moth caterpillar and the oak leaves are staying in synchrony although their timing is earlier, but the great tit hasn’t been able to respond as quickly,” says Collinson. At this stage, it is difficult to predict exactly what outcomes this may have. “Similar relationships throughout the natural world will be under pressure,” he adds.
Great tits aren’t the only animals expected to go hungry as a result of climate change. A study of marmots in North America showed that they are emerging from hibernation over two weeks earlier than in the 1980s. This early start means that many plants are not yet growing when they awaken, so the marmots are likely to face a long wait before they can tuck in.
Dormice in difficulty
Here in the UK, the dormouse is confronted with a similar problem. This small rodent fattens up on autumn fruit, nuts and berries before settling down to hibernate.
Increases in temperature however mean earlier plant flowering, which results in earlier fruiting. Blackberries for example, usually associated with early autumn, are now ripening in July in many parts of the UK. Warmer autumns also mean the dormice receive their temperature induced cues to go into hibernation later in the year.
The widening gap between fruiting and the onset of hibernation mean that dormice gorge themselves early on, but then are losing much of their fat stores during the autumn, before going to sleep on an empty stomach.
While we tend to think of climate change as being responsible chiefly for warming, it can also lead to changes in rainfall and generally more erratic weather, with mild spells being followed by cold snaps.
These fluctuations can be confusing for wildlife. “Some species are fooled into breeding much earlier than they would do because of temperature anomalies, and a return to normal winter temperatures then kills off that breeding attempt,” says Collinson.
The frog is one of the most well studied examples of this. Frogs lay just one batch of frogspawn in spring,
in response to an increase in temperature. Warm spells in winter have however misled the amphibians into spawning as early as December. Subsequent cold weather can then freeze water in shallow ponds and puddles, killing frogspawn.
The effect this might have remains unclear. “This doesn’t mean that frogs are under threat,” says Collinson, “but one can easily see that if you had a run of five, six or seven years of particularly mild spells followed by very cold weather, it would be an issue for the frog’s life cycle.”
Mild temperatures and shorter winters may sound pleasant to us, but they are definitely not good news for hay fever sufferers. An untimely spring and an extended growing season mean more allergy-triggering pollen earlier in the year and for longer periods, spelling sniffly misery for up to nine million people in the UK.
Heading North
Some species don’t cope well with warming temperatures, but are prepared to move homes in order to stay within their preferred climatic conditions, known as their climate space.
"Some of our least mobile species are also some of our rarest, and climate change poses a particular threat to them." Nick CollinsonSpecies can thus migrate further north, or in the case of alpine species, higher up slopes, in order to escape rising temperatures. The song thrush for example is expected to retreat northwards as dryer weather in the south kills off its favourite snacks – slugs and snails.
For some animals, climate change is a great opportunity, allowing them to extend their ranges as their climate space increases. This is the case for example for the greater horseshoe bat, which thrives in warmer conditions. Previously confined to the southwest of the country, it has recently been observed in North Wales.
Moving homes is nonetheless not an option for all species. “Some of our least mobile species are also some of our rarest, and climate change poses a particular threat to them,” explains Collinson. Species such as butterflies can move easily, but for mosses and lichens it is a completely different matter.
Arctic species that are already as far North as they can go, such as the Snow Bunting in Scotland, may also be in trouble. “Models suggest that they need to move north to keep up with the appropriate climate space, and if they can’t, because we’re an island and there’s nowhere to go, then there’s potential for local extinction,” warns Collinson.
A new direction for conservation
Conservation efforts are being adapted to the new pressures faced by wildlife. Instead of focusing on small, isolated reserves, the emphasis is on countering the fragmentation of our countryside in order to allow species to disperse.
“We need to make whole landscapes more sympathetic to wildlife,” says Collinson. “It’s largely about protecting what we’ve got, buffering and expanding and joining that landscape back together.”
Climate change is painting a bleak picture for much of the UK’s native fauna and flora. While no definite predictions are possible, there is an urgent need to minimise negative impacts and do what we can to help our wildlife adjust to a new climate
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