International Sakharov Environmental University Butterflies as indicators of

International Sakharov Environmental University Butterflies as indicators of climate change Pozdnyakova Anastasiya group 409 -1 Minsk, 2012

In Britain, most butterfly species reach the limit of their range due to climate. Such species are the ones most likely to show rapid adaptations to climate change. There are indications that several butterfly species are adapting and that these insects make good indicators of the likely effects of climate change on other animals.

Human activity over the past 200 years had a profound influence on our planet, so much so that it is being suggested that we are entering a new epoch: the Anthropocene.

The industrial revolution and its aftermath has led to an increase in the amounts of carbon dioxide, methane and other greenhouse gases in the atmosphere causing the climate to change.

These effects in recent decades are apparent at all levels of ecological organisation: population, life history, shifts in geographical ranges, changes in species composition of a habitat and changes in structures and functioning of ecosystems. The aspects of climate change most relevant to butterflies are global warming and changing rainfall patterns.

Butterflies, like all insects, are poikilothermic (cold blooded) organisms and climate change affects their rate of development, physiology, behaviour, ecology and reproductive success. With some species increases in populations are associated with warm, dry weather during egg laying, either in the present or previous year, while for others a high spring rainfall results in an increased population the following year.

In Britain, most butterfly species reach the limit of their range due to climate, many are at their northern margin, but some species, such as the Scotch Argus (Erebia aethiops), reach their southern margin.

Other factors affecting species living at the extremes of their ranges are adaptations to less than ideal climate conditions, restricted niches, longer life cycles or restriction to a narrow range of larval food plants. Such species are the ones most likely to show rapid adaptations to climate change, as has already been observed for the Silver-spotted Skipper (Hesperia comma)

During the late twentieth century this species had become very rare mainly because of loss of suitable habitat. It would only breed in very short turf on south facing slopes in the southern half of England.

Not only has this species become more numerous this century but it has now been found breeding on north facing slopes and in longer grass and is thus able to colonise areas which were previously unsuitable.

Because of their quick response to climatic factors butterflies make admirable indicators of climate change, especially as the Butterfly Monitoring Scheme (BMS), has accurate data sets going back to the 1970 s and many hundreds of recorders submitting data every year

There was an average temperature increase across Europe of 0. 8[degrees]C during the twentieth century and 63% of butterfly species moved their range northward. Over the past 20 years the average temperature in the Midlands region of the UK has increased by 1. 5[degrees]C. Eleven species or 25% of those at their northern limit in the south of England are extending northwards.

Conversely two species at their southern limit, the Scotch Argus and Northern Brown Argus (Aricia artaxerxes) have contracted their ranges northwards by 70 -100 km, while the Mountain Ringlet (Erebia epiphron), a species at its lower altitudinal limit has moved 150 m uphill. In the mountains of central Spain where there has been a temperature rise of 1. 3[degrees]C during the past 30 years, 16 butterfly species have moved approximately 290 m upwards.

Data from the BMS show that many butterfly species are flying earlier than in the 1970 s and have longer flight periods. The average first annual sighting of the Orange Tip (Anthocharis cardamines), a spring butterfly, was 18 days earlier in 1998 than in 1976.

Two migrant species, Red Admiral (Vanessa atalanta) and Clouded Yellow (Colias croceus) are now able to overwinter in Britain. The Red Admiral having been recorded in every month of the year for several years this century is now considered to be resident.

For the past 2 years there have been reports of Painted Lady (Cynthia cardui) seen in February, indicating that this migrant may now be able to overwinter in Britain.

The response of butterflies to weather conditions has been studied since 1976. A strong connection has been found between butterfly population fluctuations and weather in 28 out of 31 species. The northern range of most European butterflies is closely correlated with the June July isotherm. Favourable conditions, that is, warm, dry weather will aid the expansion of populations into suitable habitat where new colonies may be set up.

Although global warming facilitates expansion, this can only happen if suitable new habitat is available.

It may not be just an increase in population that causes a species to move, climate change also affects the survival of larval food plants through drought or flood so that females are forced to fly further a field to lay their eggs.

There are indications that some butterfly species are already adapting to climate change in a positive way. Such short-lived animals would be expected to adapt quickly and their success or otherwise is a good indicator of the effects such changes will have on other animals and plants.

Unfortunately for many species such habitat is at best fragmented and at worse no longer available. For species able to fly long distances (the generalists) this is not such a problem but for those unable to move far (the specialists) the lack of suitable habitat within range can lead to reduced genetic diversity and an inability to adapt which will eventually lead to the extinction of the colony.