From a different point of view, it is also important to have in mind that insect species already present in central/northern Europe tend to have high migration ability. Northern European populations have arrived there in a very short time (in evolutionary terms), i.e. since the last glaciation (about 20000 years or less). These species have rapidly moved from the glacial refugia in Southern Europe to the north, tracking climate change. Therefore, insect species present in Northern Europe are, in principle, those prone to rapidly and efficiently track current climate variations. Could this explain the perceived over-reaction?

I suspect that anthropogenic habitat alterations have, in many of these cases, augmented the opportunities to increase ranges (i.e. to colonize new habitats). For example, in Nordic countries species that benefit from clearing of boreal forest, or from drainage of moorlands and peatbogs, will more easily be able to benefit from climate change. Also affiliations with certain host plants that thrive in anthropogenic landscapes may facilitate the expansion. For certain species, roadsides and similar structures may also increase the likelihood of migrations. Finally, the mere increase of many populations in numbers as a function of more favourable climatic conditions can be sufficient just to have these populations produce more dispersing individuals.

It would also be interesting to check whether in some cases new genotypes have emerged which now achieve to transcend earlier historical distributional limits.

From a different point of view, it is also important to have in mind that insect species already present in central/northern Europe tend to have high migration ability. Northern European populations have arrived there in a very short time (in evolutionary terms), i.e. since the last glaciation (about 20000 years or less). These species have rapidly moved from the glacial refugia in Southern Europe to the north, tracking climate change. Therefore, insect species present in Northern Europe are, in principle, those prone to rapidly and efficiently track current climate variations. Could this explain the perceived over-reaction?

Thanks Konrad and Andrés! Your insights combined seem to cover well this phenomenon that has puzzled me. Thanks also to Norman even though the wisdom of your reply with barium, NASA and CIA involved somehow partly eludes my limited mind, regarding my specific question.

What about "extra-terrestrial" factors such as sunspot numbers and cosmic rays? They do display latitudinal patterns.

Hi Jesús, I don't think sun spots can have any relevance in this as the period when there has been this dramatic range expansion has co-incided with silent sunspot activity period. Of cosmic rays I don't know anything, but they sound to me a little far-fetched. Even if they have latitudinal pattern on earth, I wonder if they also show pulses of increased intensity (always thought that they are a rather constant phenomenon)

Yes, climate warming, fragmentation, etc but there also cyclic fluctuations coupled with range expansions. And such cycles may not only be purely climatic..see http://rspb.royalsocietypublishing.org/content/271/1551/1897.abstract

First of all, I want to thank you for starting this topic.

In my researches, I met an very interesting phenomenon. It is about stable flies and dairy cows. I have found it in Czech Republic, and later I get confirmation from more few European countries that the similar things happening there.

Actually, flies caused an unusual behaviour of cows. It happend in summer time, and it was demonstrated with crowding of cows in the hottes period of the day.

During the crowding there was found significant decrease in cows, of all ages (up to 30%). So that means on an averagy herd of 100 cows, producing 20 liters/day, it is 36000 l of milk in 60 days of that crowding period, i.e period of infestation. Of course that decrease was caused also by high summer T.

More on: www.archanimbreed.com%2Fcontent%2F2012%2Fabs12_04.html%23A3

The original question assumes that large range expansions are an 'over-reaction' suggesting that the optimum magnitude of range expansion would be more limited. What is the evidence that this is the case? Across almost all taxa the rate of range expansion is generally insufficient to match climate change, comparisons with other taxa may thus generate a perception of 'over-reaction' in some Lepidoptera.

Please check on these two chapters on heat and cold sensitivity of insects. http://cipm.ncsu.edu/ipmtext/chap2.pdf

http://cipm.ncsu.edu/ipmtext/chap3.pdf

Hypothetical temperature tolerance curves in Fig 2.1 of Chapter 2 clearly indicates that insects are highly sensitive to high temperatures beyond the threshold, while they are relatively less tolerant to low temperature beyond the threshold. Might be its a reason for quick expansion northwards, than southwards.

Do you have similar observations about the boreal species, which have been since a long time in Scandinavia, also in the northest parts? Those, which can not move more northwards, does their number decrease, are they getting extinct?

I think, the same phenomenon can be noticed in the Alps or other mountains with increasing hight. The movement in hight can be set in relation to the movement to north. Is the change in the Alps also over-reacted or "normal" according the climatic change?

(As I know an increase of 1,5°C corresponds with shifting in hight of about 250m)

Hello Rudolph,

there is indeed observations that some - but seemingly a minority of - species that have their southern limit of their distribution in Finland are getting scarcer and scarcer, some even become extinct in southern part of their range. This has been noted in species living in coniferous forests or mires, but in some others too like Carterocephalus palaemon whose typical habitats definitely have not become scarcer (a few year old clear-cut spots of conifer forests). For the mire/bog species it may be difficult to separate climatic factors from the extensive destruction of their habitats due to peat exploitation. However, some species like Boloria freija and frigga seem to be going exctinct also from very large bogs in southern Finland that should not be that vulnerable to larger scale metapopulation effects. If this is normal or not, I don't know, but seems something new when comparing  to even not-so-old historical records. These species are not very mobile. The northward shift of their range seems significantly slower than northward expansion of the expanding species.

https://ec.europa.eu/agriculture/sites/agriculture/files/external-studies/2008/euro-forests/factsheets_en.pdf

Hello Hamit,

Thank you very much for this report! I t seems a very thorough summary of factors affecting biota in Europe, thus also giving insights for my ponderings.

Hi guys!

Understanding the expansion of insects towards north is indeed hard when summer temperatures have not really been raising in Finland. The raise of annual mean seem to be a result of higher winter temperatures. In my mind the only climatic reason behind the expansion could be then the length of snow cover during spring time and indeed we have had since 1990's loosing snow cover earlier and earlier than we used to. This can have an enormous effect to both the length of growing season as well to the warmth absorbance due the straight solar radiation. The effect of solar radiation hours in the end of March and April have a huge energy potential which comes available the earlier snow cover retreats. For insects which are not so much interested in the temperatures in 2 m altitude in shadow as we have used to meter, this means a huge boost of available energy and can thus be seen an effect created by the warming climate.

Jaska

Thanks Jaska, I think very much likewise. But this does not explain the phenomenon observed in butterflies that like shadow or hibernate higher in trees/bushes (Limenitis spp, Apatura spp, Argynnis paphia). So your explanation, as plausible as it is to explain a lot (and I am sure that it is really relevant), still does not feel comprehensive.

Lauri,

I think the underlying process for the rapid expansion goes back to natural selection. It is based on the Malthusian idea that populations expand exponentially. The reason most populations do not expand is because few reach the age for reproduction. The predators attack the young, e.g. each butterfly lays thousand of eggs which hatch, but the caterpillars are eaten by birds.

In the case of insects spreading into Finland, warmer winters mean less insects are culled over-winter, and their expansion is exponential, especially into areas where their predators are not yet present.

I think this is due to lack of resources, anthropogenic activity, climatic changes and invasions of exotic species.

And adaptation rate of insects also augmented. To get exact answer we need first to figure out how many taxa of insects have expanded their range, what type of food they prefer, what is favourable host plant , season are for them.

So we can't say any single reason for this needed huge study on it.

" It seems that there must be other factors than climate change alone to explain this "over-reaction" Climate change activated numerous other factors connected with climate change, Unfortunately, we don`t know all these connections within the biodiversity, ecology, clima etc.