Blog - climate change
Where do butterflies come from?
An obvious answer to this question would be - caterpillars. But when did butterflies first appear? There are now some 160,000 species of moths and butterflies -worldwide. Seemingly, they appeared some 100 million years ago - in North America. They evolved from nocturnal moths in the period when flowering plants were undergoing a major expansion (in the Cretaceous period). Butterflies may have become diurnal to avoid predation by bats, or it may have been to take advantage of nectar production and availability [using the proboscis]. The butterflies and their caterpillars were able exploit the diverse range of food resources that these ‘new’ plants offered. Butterflies moved out from North America to South America and then on to other parts of the world, though they probably did not arrive in Europe until some 17 million years ago. The evolutionary expansion of the butterflies has been investigated by researchers at the University of Florida; they analysed the genetic makeup of many species (from 90 countries). They were able to build up a picture of the relationships between the various groups of butterflies and also determined their evolutionary point of origin. They also catalogued the plants eaten by the caterpillars and it was found that some two thirds of butterfly caterpillars feed on plants from the legume family (the Fabaceae - peas and beans). It is probable that the first butterfly caterpillars also fed on these plants. Research at the Georgetown University in Washington DC suggests that larger species of butterfly are ‘coping’ better with higher temperatures, associated with global warming. Bigger wings seem to offer a greater range of movement and the opportunity to find new and suitable habitats. Smaller butterflies are not faring so well. The study involved an analysis of the range of some 90 North American species between 1970 and 2010, during which period the monthly minimum temperature increased by 1.5oF. Others have analysed the butterfly collections at the Natural History Museum, using digital technology. The Natural History Museum’s British and Irish butterfly (and moth) collection is probably the oldest, largest, and most diverse of its kind in the world; some of the specimens date back over a hundred years The measurements of the various specimens were paired with the temperature that the species would have experienced in its caterpillar stage. It was found that for several species that the adult butterfly size increased as the temperature increased (during late larval stage). So, it may be that we will see a gradual increase in butterfly size as temperatures increase with global warming. Join the Big Butterfly Count ? Between Friday 14th July and Sunday 6th August , the big butterfly count will take place. For full details visit : https://bigbutterflycount.butterfly-conservation.org/about Thanks to Angus for images.
Bumblebee pollen collecting
Bumblebees (and bees) collect nectar and pollen. Pollen is a vital food, used in the various stages of a bumblebee’s life. In Spring, newly emerged queens feed on pollen, then it is used to feed its their sister workers. The workers, in turn, take over the feeding of the colony (the larvae and future queens). If not enough pollen is collected, then the colony will not thrive, which can have significant long term effects. Bumblebees are already facing many threats (from habitat fragmentation, agrochemicals and disease). The collection of pollen is a demanding process, and bumblebees will forage over a wide area. They start their pollen collecting activities earlier than many insects as they can warm themselves up by ‘shivering’, that is, rapid muscle contractions which generate heat, warming the insects up ready for flight. Bumblebees can fly in colder conditions and at higher elevations than many other insects. However, research at North Carolina State University has shown that the North American bumblebee (Bombus impatiens) can overheat when exposed to high temperatures (circa 42oC plus). So, if a bee is carrying a significant load of pollen and it is a hot day, its muscles have to work harder and the bee is at risk of overheating. A bumblebee loaded with pollen may be 2oC hotter than an unladen bee; it may be reaching its ‘thermal limit’ - a temperature at which its organs are damaged. Climate change means that many parts of the world are now experiencing extreme weather events, when temperatures can reach into the forties. [caption id="attachment_39978" align="aligncenter" width="675"] Bumblee leaving foxglove[/caption] Increasing temperatures could affect the foraging activities of bumblebees in a significant way - affecting how much pollen is collected and how much pollination takes place. If pollen collection is reduced then colony development is affected and so population numbers will be affected. Bumblebees are key pollinators in natural and agricultural systems, and if their numbers decline there will be ecological and agricultural consequences.
The Big Butterfly Count : findings
The results of this year’s Big Butterfly Count have now been published and the ‘top’ 5 butterflies are the gatekeeper, the large white, the small white, the meadow brown and the red admiral. The count is a UK-wide survey that aims to provide a measure of the state / health of our environment by simply counting the number and type of butterflies (and some day-flying moths) we see in our gardens and parks. The good news is that the Gatekeeper is making something of a comeback, being the most spotted butterfly in the count. The numbers of the Common Blue, Holly Blue and the Comma are also ‘on the up’. The Comma has been making a slow comeback for some years. This is associated with the Comma extending its range northwards. Extension of range is also seen in the Holly Blue, it is thought to be associated with climate change. Some twenty years ago, it was rarely to be seen in Scotland, but it was recorded in Edinburgh in 2006, then Ayr in 2008 and now has spread across large areas of Scotland. [caption id="attachment_24954" align="aligncenter" width="600"] Comma butterfly : photo by A J Symons.[/caption] The Jersey Tiger Moth is another species that is extending its range. Once it was to be found on Devon’s south coast, but it has spread north and east. It is now to be seen in gardens and parks in the Greater London area. These moths ‘like’ gardens, hedgerows and disturbed / rough ground. In coastal areas, they may be seen on cliffs and the upper reaches of a beach. The caterpillars of this moth feed mainly on ground ivy, white dead-nettle, bramble and the common nettle. There are differences between butterflies and moth, but there is no hard and fast rule to distinguish between them. Butterflies usually have ‘club-shaped’ antennae, whilst many moths have feathery or tapering ones. Butterflies normally fold their wings vertically over their backs, moths generally place their wings horizontally when at rest (but not all). Whilst this summer’s results offer some hope, and the warmth of this summer’s weather might be thought to have favoured butterflies, the overall trend / pattern of butterfly numbers is one of decline - for example, numbers of the Red Admiral and Meadow Brown are down, sadly a pattern seen in many insect species. The loss of suitable habitats, such as meadows and hedgerows, is thought to be a major factor in this decline.
The plight of the bumblebee
We know that insects (especially, bumblebees, bees, hover flies) are the world’s top pollinators, and we also know from many reports that many insect species are in decline. Crops such as tomatoes, blueberries, peppers, cocoa, coffee, almonds and cherries are dependent on these pollinators. Climate change, increasing temperatures and extreme weather events are affecting plants and animals across the world, and it seems that social insects, like bumblebees, are particularly impacted. Research with bumblebee colonies (at Stockholm University) has indicated that if the colonies are exposed to higher temperatures (than normal) then the workers in the colonies were smaller. This decrease in body size could affect their foraging behaviour and the collection of pollen, which would mean less food brought back to the colony and reduced pollination of plants. Studies in the United States looked at some 20,000 bees (bumblebees, leafcutter bees, mason bees etc) along the Rocky Mountains, a region which is vulnerable to climate change. It was found that the larger bees (particularly bumblebees) and those that built nests with combs were affected most by increases in temperature. On the plus side, smaller (soil nesting) bees fared better. Bumblebees would seem to have a lower heat tolerance. The loss of bigger bees, which generally can fly and forage further may again mean reduction in long distance pollination (which promotes outbreeding in plant populations). One reason why hot or hotter weather affects bumblebees is that it influences the nectar that the bumblebees collect. The balance of the various micro-organisms (bacteria and yeasts) in the nectar changes. Whilst bumblebees are attracted to nectar with some microbes in it, a small change in temperature can speed up the metabolism / growth of the microbes so that they use up more of the sugar - with the result that it is less palatable / less nutritious for the bees. Experiments conducted at the University of California have shown that bees did not ‘like’ the nectar rich in microbes, nor a sterile one - with no microbes at all. There seems to be a 'happy medium' in terms of the composition of the nectar. There seems to be a growing consensus that climate change, increasing temperatures and extreme events are pushing bumblebees (in particular) beyond their physiological limits. [caption id="attachment_38081" align="aligncenter" width="650"] Bumblebee visiting foxglove[/caption]
The opening of the woodland canopy.
Certain woodland plants are found in the understory. Plants like wood anemones, woodruff and lungwort bloom early in the year. These plants make use of a ‘window of opportunity’ when the light levels are good as the tree canopy has not developed, the leaves have not yet expanded. They use this ‘window of light ‘ to flower. However, climate change is affecting many ecosystems - including woodlands. With warmer temperatures, leaf buds tend to open earlier and the leaves begin to expand. If the window for growth is reduced, how can the wood anemones and others cope ? [caption id="attachment_38093" align="aligncenter" width="700"] wood anemone[/caption] To investigate this question, scientists based the Universities of Tübingen and Frankfurt examined thousands of preserved herbarium specimens of early flowering plants, dating back over a hundred years. The sheets not only hold specimens collected when they were flowering but also have information on ‘when and where collected’. Each sheet is a a moment in time from over a century ago. Collectively, the 6000+ sheets allowed the scientists to establish historic flowering times of woodland plants over large areas of Europe. [caption id="attachment_38094" align="aligncenter" width="700"] Woodruff[/caption] The information extracted from the herbarium records revealed that plants like wild garlic and wood sorrel now bloom some six days early than at the beginning of the twentieth century. For each 1oc rise in (Spring) temperature, their lowering has advanced by more than 3 days. This means that they have gained time in the light - in an open canopy. Whilst they may have gained time, these early flowering plants are at greater risk of frosts. It may also be that their pollinating agents may not be around - unless they too have brought forward their development / life cycle. There is some evidence that such changes are taking place. Recent work at Wytham Wood (outside Oxford) has shown that blue tits have moved forward their egg laying to 'match' the development of the oak canopy, and the appearance of caterpillars (on which the young are fed). Essentially, the timing of the food chain has changed.. Hopefully, such changes will occur in different ecosystems across the country.
Light in the darkness
Compared to past centuries, we live in a bright, highly illuminated world where even our nights are bright. Apart from the lights in our homes and offices, there are thousands of street lights. In many places, the natural 'night time' environment is no more. This 'artificial light' pollution has increased significantly in recent times (as indicated by research led by the University of Exeter). Street lights, especially the newer LED ones, may be affecting various night flying insects. It is a fact that insect populations in general are under threat from The loss of woodlands, forests, heathlands and meadows (often to agriculture) The intensive use of pesticides Climate change / extreme weather events Pollution of rivers / lakes (eg. Nitrate / phosphate pollution leading to eutrophication). Now the intensive use of artificial light is thought to be affecting night flying insects, such as moths. Moth populations are in decline, for example, the Buff Arches population, has declined in number by 62% since the 1970s. However, the effects are not limited to moths but also birds, bats and wildlife that feed upon them (or their caterpillars). The UK Centre for Ecology and Hydrology suggests that streets bathed in light may:- Deter nocturnal moths from egg laying. Make the night flying moths ‘easier targets’ for predators (such as bats). Affect the feeding habits of moth caterpillars. A number of investigations have been initiated by CEH, Newcastle University and Butterfly Conservation. The work involved surveys of grassland and hedgerows in southern England (Thames Valley) some lit by streetlamp, others unlit. The areas that were exposed to night time lights had roughly half the number of caterpillars as compared to the unlit areas; (the hedgerows reduction was 47%, and 33% in grass margins). In another investigation, LED lighting was set up in fields, caterpillars numbers in such fields were reduced. It would seem that night time light affects the feeding behaviour of caterpillars. Quite how and why is to be determined. LED lights are being using more and more, as they are brighter, cheaper to run and more energy efficient. LEDs emit more blue light than older forms of lighting. It is likely that the impacts of light pollution on night flying insects will increase. This, in turn, will effect of other species, such as hedgehogs which need many, many caterpillars to feed themselves and their young. The loss of insects, such as bees, ants and beetles is occurring at a worrying rate, indeed faster than the loss of mammalian, avian or reptilian species. The loss of insects has far reaching consequences for ecosystems - as they provide food for many vertebrate species and they acts as pollinating agents for many flowers and crops. https://youtu.be/Rnsz7JtBmJw
Drought and pollinators
Climate change is affecting all parts of the world, from the melting of the ice caps in Antarctica, to droughts in Australia and California. On a more local level, we may see changes in our rainfall pattern. Certainly for many parts of the UK, it has been a very dry start to the Spring, coupled with some very cold nights. Cold and dry weather affects plant growth in significant ways. Warmth is needed for a plant’s enzymes (catalysts) to work, speeding up reactions and allowing growth. Similarly, if water is in short supply, growth is stunted; plants do not realise their full ‘potential’. They are smaller overall as is the number and size of flowers that they produce. Flowers attract visitors by colour, size and scent; or combinations thereof. Smaller and fewer flowers, in turn, have ‘knock-on effects’ for their pollinators - bees, bumble bees, hoverflies etc. The effects of drought on pollination has been recently investigated by researchers at Ulm University in Germany. They studied the effect of drought on field mustard (aka Charlock) : Sinapsis arvensis. This is an annual plant that is to be found in fields, waysides and field margins across Europe. It has bright yellow flowers, with four petals. It is visited by many different pollinators (it cannot self-pollinate). The researchers compared the number of visits by bumblebees (Bombus terrestris) to drought-stressed plants to well-watered ones. The data showed that as the number and size of the flowers decreased so did the number of pollinator visits. [caption id="attachment_21589" align="aligncenter" width="600"] Bumblebees also favour the teasels[/caption] The ‘attractiveness’ of the plants / flowers to pollinators was reduced, and it is possible that the smaller flowers were more difficult for relatively large pollinators (like the bumblebees) to ‘deal with’. If pollen movement is reduced, then fewer fruits / seeds will be set and (insect pollinated) plant populations could decline. The effects of reduced rainfall and water stress need to be considered alongside the declining number of pollinators. The reduction in pollen movement has lead some to speculate that it might lead to a selective pressure for self-pollination / self-fertilisation, with plants dispensing with the need for visiting insects. Other Woodlands blogs have reported on the falling numbers of insects / pollinators. Featured image : garlic mustard.
woodlands web updates 10.
Bees and solar parks As the country tries to move towards carbon zero, so we see more and more solar parks / farms ‘springing up’. Whilst they do create clean energy, they also take up a lot of land, and it is important to see if such solar parks can offer other commercial or environmental benefits. One suggestion is to place honeybee hives on such parks. The bees could provide a pollinating service to surrounding crops / farmland. Researchers at Reading and Lancaster Universities have studied detailed land cover maps / crop distribution patterns to estimate the economic value of deploying honeybees in solar parks. Their investigations suggest that a variety of crops from oil seed rape, soft fruits to apples and pears could benefit from such an arrangement. The benefits would vary across the UK, with the benefits being greatest in the East and South of the country. Care would need to be exercised though to ensure the placing of hives did not disturb the foraging of wild pollinators, such as carder bees, hoverflies etc. Are plants sulphur deficient? Much has been written about the importance of plants nutrients, especially NPK; that is to say nitrogen, phosphorus and potassium. However, little is said about sulphur. However, researchers in Groningen, Graz and Cologne have been looking at the effects of sulphur deficiency, particularly in relation to the colour and shape of the flowers formed. The work focused on Brassica rapa, a member of the mustard family. When it was subject to ‘mild’ sulphur stress (by limiting the sulphate in the growth medium), the flowers that formed were smaller and paler - not the usual bright yellow. They were also likely to be mis-shapen. Colour and shape are features by which pollinators recognise flowers and then visit them. Pollen production by the flowers was also affected; smaller pollen grains were formed. This may in turn affect the pollinators who visit the flowers foraging for food. In the relatively recent past, sulphur deficiency may not have been a problem due to acid rain, which would percolate through the soil, forming sulphates. [In the twentieth century, acid rain formed as a result of the release of sulphur dioxide (and nitrogen oxides) into the air through the burning of fossil fuels. However, various clean air acts have ensured that there is now much less SO2 in the air.] Annual rings, water availability and earthquakes. Christian Mohr (scientist from the University of Potsdam) was studying the transport of sediments in rivers in Chile in 2010 when a massive earthquake shook coastal areas of the country. When he was able to return to his studies, he noticed that streams in the valleys were flowing faster. He reasoned that this was because the earthquake has literally shaken up the soil, so that it was now more permeable and ground water could more easily flow down from the ridges. As a result of increased water supply, he thought that trees down in the valleys would grow more than those on the ridges. He and colleagues drilled out plugs of wood from valley trees and ridge trees, and back in Potsdam they examined the tree rings under a microscope. They also looked at the uptake of different isotopes of carbon as a measure of photosynthesis. They found that trees from the valley floor experienced a small but noticeable growth after the earthquake, and this lasted for weeks or months, whereas the trees of the ridges grew more slowly. It is possible that analyses like these, when combined with other information, could help identify significant historic disturbances. Rising temperatures. Recent years have seen periods of very hot temperatures, Such extreme weather events have been seen not only in the UK but across the globe (Arizona , Victoria Australia, Indonesia). Extreme heat (and drought) have been known throughout history, but it would seem that extreme events are now more common. The first two decades of this century are among the warmest on record; this warming is associated with increasing levels of greenhouse gases (due to human activity). Prolonged heat is not without its effects on us, it leads to sweating, teaches, fatigue, dehydration and heat exhaustion. The very young and the elderly are most at risk from ‘heat waves’. A 2003 heatwave across Europe is said to have caused several thousand 'excess' deaths’, mainly of the elderly. Even gradual but sustained warming of the climate can have its effects. For example, Silwood Park (Imperial’s research station) has commented that though it is now November, they have not recorded a single frosty night - normally they would expect to have three in a ‘normal’ October. Snowdrops are appearing earlier, and some migratory species are changing their pattern / timing of migration. Across the world, different species are being affected in different ways. Thick billed murres (type of guillemot, found in and around the Hudson Bay) have a high metabolism to deal with the cold waters into which they dive - they are cold adapted animals. On warm days (when the temperature is 21cC or above) they are dying whilst sitting on their nests - incubating their eggs. They struggle to keep cool, if they spend more time in the water then they leave their eggs exposed to predators (like gulls and arctic foxes). Similarly boreal and arctic bumblebee species are sensitive to heat stress, succumbing to stupor; other work indicates that some European / mediterranean species are now to be found in areas of the arctic circle - as a result of changing climatic ‘norms’. Wild dogs are adapted to deal with heat, but if the temperature goes beyond a certain point they stop hunting, consequently their pups / offspring are less likely to survive. Warming temperatures not only affect animals but they also contribute to the increasing number of harmful algal blooms (in lakes and off shore regions). These blooms can be dangerous to many animals (including humans) and when they die back they ‘suck’ oxygen out of the water - creating ‘dead zones’. One species of alga (Karlodinium veneficum) which is known to produce toxins has been shown to acclimatise to higher temperatures (up to 30cC). As climate change and research continues, we will no doubt see further examples of how animals and plants are being affected by changing temperatures / climate .