Butterfly decline in the UK some new hypotheses by Dr Chris Barnes, Bangor Scientific and Educational Consultants. E-mail manager@bsec-wales.co.uk
First published on-line without full reference list 22nd August 2016
Abstract
Some
existing and brand new hypotheses of butterfly decline causation are raised and
discussed. Climate is shown to be a
relatively weak factor with only summer
temperatures being relevant in a linear regression study. Neonics are also relevant as are ghlyphosphates.
However, the strongest single factor found in UK butterfly(permanent)
decline by linear correlation appears to be the increasing prevalence of white
skies due to Aviation cirrus type
cloud or persisting contrails. These
disrupt light polarization essential for butterfly navigation, feeding and
mating. Transient variations in
butterfly pollutions
may also arise as a result
of new radio frequency technologies.
These disrupt cryptochrome blue light sensing
and magnetic navigation and the butterfly immune response. Bees and other insects and birds may be
similarly affected by both white skies and RF. The decline of birds is perhaps
inevitable, whenever insects are in decline as they are integral parts of a
food chain. The fact that the decline of
farmland birds is more than double that of woodland and sea birds suggests a
problem with the farmland environment but the fact that all birds are in
decline suggests more than one reason
for decline with a second or additional reasons extending beyond farmland (
i.e. simple pesticide use) and by
extrapolation there may perhaps
similarly be expected to be more
than one reason for the decline of pollinators and in this case butterflies,
especially as their caterpillars form an essential part of bird food
chains.
UK
butterflies appear to be in a state of severe decline for a number of
reasons. This work finds that the
strongest reason for their decline (73% of current rates) is the increasing
prevalence of cloudy skies, especially aviation cirrus here in the UK. Secondary reasons include the neonicotinoid family of
pesticides and the orgnophosphate herbicide glyphosphate.
Pesticides and herbicides possibly account for the other 30% or so of current
decline. Transient declines (between
10-30 % of the 1990 total numbers) may have also occurred with the introduction
of various new radio frequency communication and broadcasting
technologies.
The
following further work is crucial to confirming the above hypotheses and
preliminary findings:
1. Establish butterfly numbers
underneath UK air-lanes compared with numbers well separated from the same.
Flight radar evidence already suggests that the most overflown areas are those
with most butterfly decline. This explains
why even thermophilic butterflies are declining in Germany when theoretically their
numbers should
be improving in a warming climate.
2. Establish decline ( if any) due to 4G
communications technology which ought to
show in 2012-2017 data.
3. Fight for moratorium on the use of
'round up' and similar glyphosphate weed killer
products, to re-assess their effect.
Introduction
Butterflies, partly because of their very short life cycles, are fast becoming accepted as new and exciting environmental indicators (ref). Presently, however, the precise factors to which they are sensitive are neither well known nor quantified. This present paper aims to demystify the situation somewhat. Any individual with an eye on their garden or the countryside in general will not be able to help but notice the dramatic decline in butterfly numbers in recent years. This has been documented by Defra for the period 1990-2012 see https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/389401/agindicator-de6-18dec14.pdf
The
Defra report states that although numbers fluctuate from year to year,
presumably as a result of climatic conditions, there has been a more
significant decline since 2008.
Butterflies
are, along with bees, essential pollinators.
Another Defra report describes the decline of pollinators in more
detail see https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/493028/UKBI_2015_v3a.pdf
The above references show that between
1970-2012, 3/4 birds, butterflies, moths and mammals populations of priority species have declined and distribution dramatically dropped.
1980-2010, Butterfly populations have crashed. More than 1/2 of all pollinator species, e.g. bees, hoveflies, are less widespread and declines are more exaggerated in more recent years.
1970-2014 breeding birds: decline 20% woodland, farmland 54% birds, 2014 seabirds 27% lower 1986 levels.
The decline of birds is perhaps inevitable, whenever insects are in decline as they are integral parts of a food chain.
The fact that the decline of farmland birds is more than double that of woodland and sea birds suggests a problem with the farmland environment but the fact that all birds are in decline suggests more than one reason for decline with a second or additional reasons extending beyond farmland and by extrapolation there may perhaps similarly be expected to be more than one reason for the decline of pollinators and in this case butterflies, especially as their caterpillars form an essential part of bird food chains.
Over
the past decade,
neonicotinoids ( so called
neonics for short) have been shown to be associated
with bee decline. There are indeed hundreds of papers, far too many to
reference here which discuss the link
and the mechanisms. Others have posed the
question can neonics be harmful to butterflies ( refs).
I
will examine the evidence for this below.
I
have also very recently noticed that some species of butterfly here in North
Wales are having severe difficulty in orienting themselves and in choosing
flowers on which to settle. Such
difficulty in itself might be expected to lead to butterfly decline because such difficulty might be
expected to prevent mate selection, mating, foraging and feeding. This has prompted me to explore if there
are other potential mechanisms for decline besides chemical exposure. I will discuss my findings below. I have also noticed that butterflies are
avoiding urban gardens and that Woodland species of butterflies are not so
badly affected.
Data
The
data used in this study is essentially that of the Defra report and data has
also been taken from the Met office website regarding UK Climate Anomaly
at http://www.metoffice.gov.uk/public/weather/climate-anomalies/#?tab=climateAnomalies
Methods, Results and Discussion
1.
Climate
Defra
has suggested that the random fluctuation of butterfly populations is most
likely due to weather. To test this
hypothesis I constructed linear regression algorithms of butterfly population versus
temperature anomaly for the period 1990-2013.
I also examined the effect of springtime, summertime and autumn
temperatures. For the entire period
the regression values were
Spring
= .06
Summer
= .53
r=.47
DF=23
The two-tailed P value equals 0.0064
By conventional criteria, this difference
for the Summer result is considered to be very statistically significant.
Autumn
=.14
There
is no statistical significance to the spring or autumn results.
On
the basis that I have noticed significantly whiter skies in the UK and fewer butterflies since
about the year 2000, I decided to produce individual summertime
regressions for the period 1990-2000 and
2001-2013.
The
resultant algorithms are:
1990-2013 % population = 68.4 + 8.6*DeltaT
1990-2000 % population =
82+ 11.7* Delta T
2001-2013 % population = 55.6 + 12.15* Delta T R=.53
The
regression factor was strongest for the latter period.
The
fact that the regression factor weakens as more data is added is indicative of
the involvement of multiple processes
for the causation of butterfly decline.
1.
Neonics
In
seeking what these multiple processes might be, I decided to explore the part
that neonics might, if any, be playing.
I
plotted the Defra data against year number and applied a best sinusoidal fit.
It can be clearly seen that the plot is relatively flat until 1994 and flat
again but lower after 2011. The very
dates when neonics were first used and when the
present moratorium came into play. I
recently contacted DEFRA and the Welsh Assembly Government regarding the state
of play of
Gwynedd's Butterflies in the present summer (2016) to enquire if the moratorium
had come to an end. The answer was
that it had not. I was surprised,
however, to find out that emergency arrangements had been made to allow the
spraying of some oil seed rape in the second half of the summer of 2015 ( ref) and was somewhat disappointed that they had not
personally confirmed this.
Neonicotinoids
were first used extensively on UK farmland in 1994 and the present moratorium
came in to force in 2011. However, the
data is far from a good fit and other factors may also be at play especially as
other mathematical models show continued decline.
2.
Glyphosphate
Glyphosphate is
being more widely used on wheat than ever before and as a garden weed killer.( Refs) It is
more toxic to humans than its declared intention as a herbicide (refs). It is
being found in significant concentrations in human urine (
refs), is an endocrine disruptor ( refs) and may be carcinogenic to
humans ( refs). Yet by some madness it is still allowed as an agricultural and
garden herbicide. It also disrupts
some insect communities by altering weeds distributions. (refs)
I
thus wondered if glyphosphate may be altering
butterfly populations. I made the linear plot below.
I
find a linear relationship between glyphospahte
application and butterfly decline in recent years but with what I thought was a fairly weak
correlation, R=.55. Further inspection,
however, due to the available number of degrees of freedom shows it to be
significant.
P Value
Results
r=.55 DF=16
The two-tailed P value equals 0.0180
By conventional criteria, this difference is considered to be
statistically significant.
My guess
is both habitat destruction and direct organophosphate toxicity may be
responsible here.
There has
been a tremendous recent upsurge in TV weed killer advertising and local
councils weed spray all urban verges. My
guess is this will drive most urban butterflies into more rural locations,
possibly distorting butterfly counts which rely on the public at large.
3.
White skies/the effect of increased
air travel on butterflies.
I have previously proposed a hypothesis wherein RF radiation with rotating magnetic vector may effect butterflies via cryptochrome. I will further discuss the effect of the RF background on butterfly decline later in this paper. As part of the cryptochrome system insect/butterfly eyes are tuned to blue light but specifically polarised. As early as 1965 von Frisch (1965), demonstrated that other insects (honeybees (Apis mellifera)) respond to skylight polarization and use it for navigation. Not only do butterflies produce polarisation sensitive colour in their wings ( ref) they also feed and navigate and select mates accordingly (refs). In recent months I have noticed urban and garden butterflies in Gwynedd behaving strangely, seemingly unable to orient towards the sun or to settle on flowers properly. I thus wondered if something is effecting their polarisation detection system.
Polarization-sensitive colour originates from polarization-dependent reflection or transmission, exhibiting abundant light information, including intensity, spectral distribution, and polarization. Such is seen with butterfly wings. Light reflected from waxy plant surfaces is partially linearly polarized, see Wehner and Bernard (1993). A wide range of butterflies are physiologically sensitive to polarized light, but the origins of polarized signal have not been fully understood. Zhang et al (REF) have systematically investigated the colourful scales of six species of butterfly to reveal the physical origins of polarization-sensitive colour. Microscopic optical images under crossed polarisers exhibit their polarization-sensitive characteristic, and micro-structural characterizations clarify their structural commonality. In the case of the structural scales that have deep ridges, the polarization-sensitive colour related with scale azimuth is remarkable. Periodic ridges lead to the anisotropic effective refractive indices in the parallel and perpendicular grating orientations, which achieves form-birefringence, resulting in the phase difference of two different component polarized lights. Simulated results show that ridge structures with reflecting elements reflect and rotate the incident p-polarized light into s-polarized light. The dimensional parameters and shapes of grating greatly affect the polarization conversion process, and the triangular deep grating extends the outstanding polarization conversion effect from the sub-wavelength period to the period comparable to visible light wavelength. The parameters of ridge structures in butterfly scales have been optimized to fulfill the polarization-dependent reflection for secret communication. The structural and physical origin of polarization conversion provides a more comprehensive perspective on the creation of polarization-sensitive colour in butterfly wing scales.
Butterflies
of the genus Papilio have polarisation-sensitive
photoreceptors in all regions of the eye, and different spectral types of
receptor are sensitive to different e-vector orientations. Zhang studied the
consequences of this eye design for colour vision in behavioural tests and
found that Papilio spp. see false colours due to the
polarisation of light. They discriminate between vertically and horizontally
polarised light of the same colour in the contexts of oviposition and feeding.
The discrimination depends on the spectral composition of the stimuli. In the
blue and probably in the green range, discrimination does not depend on
intensity. However, colour discrimination is influenced by polarisation. Thus,
colour and polarisation processing are not separated in the visual system of Papilio spp. From their results, they proposed hypotheses about which
photoreceptors contribute to colour vision in Papilio
spp. and what adaptation value such a system might have for the butterflies,
reference at http://onlinelibrary.wiley.com/doi/10.1002/2013GL058840/pdf.
Sweeney
et al also comment on the use of polarisation by Heliconius
butterflies.
Holger
G. Krapp Department of Bioengineering, Imperial
College London, South Kensington Campus, London SW7 2AZ, UK has further discussed how Insects Find
Their Way by Watching the Sky and the polarised light it produces.
It
seems to me that anything which disturbs sky colour and/or skylight
polarisation will impact heavily on pollinators such as bees or
butterflies.
The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can even be used to detect super-thin cirrus clouds having an optical depth of only ~0.06 and super-thin liquid water clouds having an optical depth of only ~0.01. Such clouds are too thin to be sensed using any current passive satellite instruments, see Sun et al 2014, http://onlinelibrary.wiley.com/doi/10.1002/2013GL058840/full yet at ground level and at some solar zenith angles they may completely rotate the said field from parallel to perpendicular. I postulate that this would severely disorient pollinators such as bees and butterflies.
As
more and more air travel takes place, I would expect more and more white skies
and cirrus (aviaticus) cloud. I would thus expect
more and more polarisation disturbance to the blue sky scenario and more and
more confusion for insects such as butterflies.
To
test this hypothesis, I plotted the percentage of butterfly population since 1990 against revenue
passenger kilometres ( an indicator of amount of air travel ) in the same
period, see below. As air travel has
intensified and as modern aero-engines and fuels have evolved, more and more
aircraft contrails spread out and persist across the skies as a cirrus type
haze.
A
very strong correlation is found R=.86.
This also exceeds temperature and chemical pollution effects.
In
North Wales we
have to date in 2016 had a warm but very cloudy summer with clear days literally countable on one hand
and even on dry days the sun often does not break through the cirrus haze until mid -afternoon. I would
expect this too may disrupt insect and even human circadian rhythms. Neonics
(apparently?) remain banned but urban butterflies, particularly
the Small Tortoiseshell and Peacock species appear all but extinct. Both these species were present as normal in
March and April of 2016. Richard (Rik)
Fox of Butterfly Conservation
also comments on the 2016 UK weather in general as having a cold, late spring followed by a warm
but extremely wet and sunless summer.
The results of this present study seem to indicate that it is not cloud
or lack of sunshine per se which is contributing to butterfly decline but more
likely it is specific types of cloud and light polarisation scenario brought on
by the almost exponentially increasing amounts of air travel persisting at
present.
Further discussion of white skies
effect
A
test of the white skies hypothesis would be to evaluate butterfly populations underneath
air corridors as compared with those well way.
There is already considerable support for the idea.
Butterfly Conservation vice-president is Mr Chris Packham. Mr Packham has recently stated that butterflies in England are declining
while those in Scotland show no long-term trend. He has blamed this on
climate change.
It
seems to me that air traffic density offers a far better explanation. Below is a typical flight radar image of air
traffic over Britain and Europe.
I
note that Scotland is one of the least overflown areas and has least butterfly
decline.
On German Butterfly decline Jan Christian Habel, one of the study researchers from TUM's Terrestrial
Ecology Research Group.
Despite
climate warming, thermophilic species - those that like warm and dry conditions
- also appear to be in decline.
Nitrogen
input to agricultural land has been blamed for promoting too much plant growth
and too much shade close to ground.
Light
polarisation effects due to aircraft are of course not on the agenda. But reference to the flight radar image
shows Germany to be one of the most heavily overflown parts of Europe.
5. The
Radio Frequency (RF)
Environment
I
have advanced a hypothesis elsewhere ( reference) as to why butterflies may be impacted by 4G
mobile communications systems.
It
would be interesting to see if any stepwise declines can be seen in the Defra
data corresponding with the dates of introduction of any other RF technologies. I predict stepwise, rather than permanent
declines because adaptation happens faster in organisms with short life cycles.
For example, Sawicki and Denholm (1984) have
discussed insect adaption to various insecticides.
Butterfly
declines have actually been recorded since the 1970's and this period does
coincide with the introduction of UHF TV broadcasting.
The
Defra data for recent declines is shown below.
I
have previously suggested that from their body sizes most butterflies would act
as dielectric resonators at frequencies
from about 600-1000MHz.
2G
mobile telephony was introduced in Britain in 1993 and a step wise decline of
20% can be seen in all butterfly populations at that time. Similar changes are seen in the EU butterfly
data where mobile telephony followed a similar historic progression. Not all EU countries have the same spring
and summer weather conditions as Britain so this points to butterfly decline as
involving far more complex factor(s) than
previously suggested by biologists and conservationists.
DAB
was introduced in 1999. Because of the
much longer wavelength I would not expect to see an effect and as predicted no
such effect is noted.
3G technology was introduced in 2001. 3G operates predominantly at 2100 MHz and so I would not expect such a pronounced effect, but there may be some effect as individual parts of a butterfly's body might resonate. A 10% stepwise decline is noted in 2001.
DVB
terrestrial TV was introduced mainly between 2010 -2012 in Britain and we see a
corresponding 30% decline. One should
perhaps not read too much into this however, as firstly these frequencies were
already in use for analogue TV and secondly the summers of 2011 and 2012 were
both significantly colder than the long term average.
As
expected the effects of RF on butterfly populations appear to have been
transient. I postulate that RF
interferes bi-modally with the cryptochrome
system. Firstly, rotating fields and
these are expected to be far more of a problem with 4G but data is not yet
fully available.
Secondly, I would imagine RF may interfere with the insect immune response in a way not unlike that proposed by Lauer (ref|) for human carcinogenesis. For instance, it is known that the Immune response in insects and mammals has certain common origins. Insects have a highly efficient immune system. In response to a bacterial attack, their fat body (the equivalent of the liver in mammals) synthesizes a whole range of peptides with an antibacterial and antifungal effect. For several years now the "Immune response and development in insects" Laboratory (CNRS, Strasbourg) led by Jules Hoffmann, has been studying the mechanisms that control the antimicrobial response in insects, using the Drosophila as their model. Thanks to a genetic approach developed by Bruno Lemaitre, several different control pathways (or "cascades") governing the expression of the genes that code for antimicrobial peptides have been identified. This researcher showed that one of these cascades, the Toll pathway, is structurally and functionally similar to a specific pathway in mammals responsible for the expression of the genes involved in the acute phase immune response. This research demonstrates that the cascade involved in the immune response must have appeared early on in the evolution of eucaryotes. It also illustrates the striking similarities between the antimicrobial response in insects and the innate, non-adaptive response in mammals
1. In mammals, the acute phase response refers to the
changes in the bloodstream during primary response to infection. In this
response, the blood cells and liver produce a whole range of proteins.
2. A mammal's primary response to infection depends on innate immunity, which
is based on a variety of mechanisms that recognize and respond to the presence
of a pathogen (including, among other things, the acute phase response). This
response is followed by the adaptive response mediated through clonal selection
of specific lymphocytes, which provides long-term protection against a given
pathogen.
The
somewhat surprising and almost counter-intuitive predictive upshot of changes
in the RF environment are transitory. According to Lauer, for carcinogenesis in
humans this is connected with the way in which the body and thymus in
particular manufactures and stores different populations of T-cells. As far as is presently Insects only have an
innate immune system, maybe the above finding calls this into question?
Conclusions
and further work
UK
butterflies appear to be in a state of severe decline for a number of
reasons. This work finds that the
strongest reason for their decline (73% of current rates) is the increasing
prevalence of cloudy skies, especially aviation cirrus here in the UK. Secondary reasons include the neonicotinoid family of
pesticides and the orgnophosphate herbicide glyphosphate.
Pesticides and herbicides possibly account for the other 30% or so of current
decline. Transient declines (between
10-30 % of the 1990 total numbers) may have also occurred with the introduction
of various new radio frequency communication and broadcasting
technologies.
The
following further work is crucial to confirming the above hypotheses and
preliminary findings:
1. Establish
butterfly numbers underneath UK air-lanes compared with numbers well separated
from the same. Flight radar evidence already
suggests that most overflown areas are those with most butterfly decline.
2. Establish
decline ( if any)
due to 4G communications technology which ought to show in 2012-2017 data.
3. Fight
for moratorium on the use of 'round up' and similar glyphosphate
weed killer products, to re-assess their effect.