Climate Change Canaries?

Signs of the impact of climate change due to global warming are widespread now, at least on the global scale. Rising sea levels, melting ice caps, disappearing glaciers and acidification of the oceans are all well reported.

But what of the affects of climate change on wildlife here? Can any of the reports of unusual sightings of migrant species be due to it, as has been speculated?

There are reports of summer migrant birds now over-wintering and sightings of once rare butterfly visitors also increasing. Numbers of Blackcaps, for example, are no longer returning to their origins in north-eastern Europe but are over-wintering here.

While some visitors are finding us to their liking and staying over, native wildlife is also seemingly beginning to adapt to living in our warming UK climate.

Birds such as the Dartford Warbler are gradually moving northwards and some species are nesting some weeks earlier in the spring in response to warmer temperatures.

At the WSBRC we get a number of unusual sightings in among the thousands of native species records submitted each year. Some of these relate to migrants found at an unexpected time of year or location in Wiltshire.

A recent example was the discovery by County Recorder for macromoths, Marc Taylor, of a Rannoch Looper moth, not thought to have been seen here before.

Little Egrets, a form of small white heron, were once only summer visitors but are seen quite frequently in Wiltshire all year now, especially around the Cotswold Water Park on the northern boundary of the county.

The huge influx of Painted Lady butterflies in May, in numbers not seen before by many observers, also caused speculation that this was an effect of climate change.

The national charity, Butterfly Conservation, believe this was an unusual variation of a natural migration rather than anything else. They have produced a report, though, indicating that moth populations are moving northwards at a steady pace, as average temperatures rise under the influence of global warming

Using historical records they highlight the Orange Footman moth, which has moved northwards by 150 miles in a few decades or the Lyme Hawk-moth which has moved northwards by nearly 70 miles.

All around us wildlife is continually responding and adjusting to its environment. It has to for its survival, nature being an unforgiving taskmaster.

Animal species innate behaviours develop over time to suit their immediate habitat, to make best use of the opportunities presented to them to survive and thrive.

While this fit may be a close one and its shape well defined, like water that fills a depression to form a pond, it is contingent and unbounded. As all environments change over time, so the wildlife dependant on them must follow and adapt too, by such means do species evolve, after all.

The time taken can vary from being very gradual over millions of years, or fast over thousands, to rapid, over decades. This latter case was famously exemplified by the Peppered Moth changing from white to black forms and back again in response to varying industrial pollution affecting its visibility to predators.

In the face of all this complex and ongoing change, how do we decide when exceptions in recorded animal populations, locations or behaviour are naturally occurring variations or the unusual responses to stresses imposed by artificially induced phenomena, such as climate change?

Shifts in the migratory patterns of some species may be one of the early indicators of underlying environmental change, the eponymous mine canaries that warn us that all is no longer well.

The British Isles are the nexus of many migratory routes and this dramatic seasonal process is increasingly well observed, if far from fully understood. A wide range of birds from colder climes like Iceland and Scandinavia, the near continent, or much warmer regions like North Africa, come here each year to feed and breed.

Many species of butterfly and moth, whales and dolphins, Basking Shark, Sunfish and even Leatherback Turtles from the Caribbean, all journey over many miles to benefit from our more temperate climate and unique nutrient rich confluence of Arctic and tropical waters.

The success of this extraordinary natural phenomenon can rely on a linked sequence of separate environments supporting animals over the many hundreds, maybe thousands, of miles as they make their strenuous journey in stages.

Migration is especially vulnerable to habitat changes at any stage in a long and possibly perilous journey through those various environments. Like stepping stones across a fast flowing brook, if even one step should dip or wobble the whole passage over could falter or stop.

Wiltshire may not be able to boast Leatherback Turtles, but it does have many migrant species that are critically reliant on a productive stay over in our county during winter or summer months. These may include familiars like Swifts, Starlings, numerous Warblers or Thrushes, many species of butterfly or moth, such as the Painted Lady or Humming-bird Hawk-moth.

But seasonal visitors can arrive or depart earlier or later than expected or in greater or fewer numbers. Are these part of a few years’ natural variability in a complex web of interdependent factors such as prevailing winds, insect food availability or suitable nest sites, or are they harbingers of some more sinister underlying shift?

It is, at present, difficult to tell. Although many migratory patterns and routes may have been in place since the last ice age, i.e. for some thousands of years, knowledge of the underlying mechanisms and their predictability is not complete.

In the same way that no single extreme or unusual weather event can be laid at the foot of climate change, nor can one unusual record of a species found out of time or place point to an adaptation or underlying environmental shift.

But a repeated sequence of atypical sightings over time, like a similar sustained change in the usual expectations of seasonal weather, could point to some deeper underlying effect.

As a dramatic and widely observed phenomenon, migration of species may also provide a sensitive early indicator of how and when climatic changes will affect their ranges and hence also resident wildlife populations and their habitats.

The WSBRC gathers data continuously over time about populations of many wildlife species, including migrants, in numerous locations and habitat types across the county. This gradually builds the body of knowledge to allow the mapping of population densities and distribution patterns necessary to permit subtle changes to become apparent.

However, proving a clear causal link between shifting migration to our small part of the UK and climate change is always going to be problematic, or even impossible. There is a huge number of natural variables in the mix, other human impacts such as direct habitat destruction here or elsewhere and a vast amount of data that still needs to be gathered and analyzed.

Only by diligently assembling records of species from numerous sources and locations, repeated over a long period of time to build a large database, may our understanding grow of how changes in migratory patterns reflect possible impacts for our native wildlife.

The early pointers that are be beginning to emerge, as briefly illustrated above, are certainly causing growing concern about the current effects and possible long term consequences of climate change for wildlife in the UK, visiting and resident.

The RSPB and BTO, for example, have both undertaken studies to measure and monitor more precisely bird migration patterns to improve our basic knowledge of this natural process.

Careful ongoing recording of a broad range of wildlife in Wiltshire, through the offices of the WSBRC, the County Recorders and many volunteer schemes, is an important contribution to helping map, understand and predict the effects of climate change on our natural environment.

Your individual records, or involvement in a monitoring scheme, help us with this task of building a dynamic wildlife database. The knowledge gathered can help point to changes now emerging, or imminent, and develop the conservation management of habitats required to help alleviate at least some of the anticipated impacts.

In the scheme of small things that we can all do to help wildlife cope with the damage humankind has inflicted upon it, recording the wildlife you see at a location near you and repeating this over time is a worthwhile step to take.

To find out how you can start recording Wiltshire's wildlife and help with the WSBRC's important work follow this link.

You can read about the Butterfly Conservation report on moth migration and climate change using this link.

The effects of climate change on bird migration patterns are outlined on this page of the RSPB’s website.