Insect pollinators are currently in decline.  This is, in part, due to the loss of habitats and foraging resources for pollen and nectar.  Pesticides, like the neonicotinoids, don’t help. Lawns and pollinators. “No mow May” has been promoted by Plantlife to  provide a feast for pollinators,  tackle pollution,  reduce urban heat extremes, and  lock away atmospheric carbon Lawns in gardens, parks, recreation grounds etc. represent a significant proportion of green space in cities, towns and villages. If these spaces and suburban lawns are managed with pollinators in mind, then they could become an important source of foraging resources.  Now, there is evidence accumulating that this is the case.  A  recent study used the lawns at Ministry of Justice prison and court sites.   Each site contained four patches,  A patch mown as normal every two weeks - the control  A patch mown every 4 weeks A patch mown every 6 weeks A patch mown every 12 weeks Weekly surveys of pollinators and flowering plants were made throughout June to late August. Butterflies, bees, bumblebees, hoverflies and beetles were recorded as pollinators.   The patches that were mowed less frequently (6 and 12 weeks) had many more pollinators [in fact 170% higher than the 2 week patch], and more flowers.  The most common plants recorded included selfheal, daisy, dandelion, creeping buttercup, and white clover.  Apart from the increase in biodiversity, the patches were ‘visually pleasant’, contributing to the wellbeing of staff / prisoners and saved on lawnmower fuel (cost). Details of the study : https://conservationevidencejournal.com/reference/pdf/12801 Farms and Pollinators. Farms and their crops, such as clover and oil seed rape, can offer a rich supply of pollen and nectar to pollinators.    The ‘richness’ of this supply can draw pollinators away from more natural areas.  However, the pollinators can go from ‘feast to famine’, when the crop has finished flowering.   A Swedish study has followed the behaviour of farmland pollinators after clover flowering.  They found that if natural areas were available after the flowering of the clover, then pollinators [like different bumble bee species] became more selective in their foraging.  This reduces the intensity of competition between the various pollinator species.  Areas of natural vegetation on farmland are therefore important in helping pollinators adapt after crops (such as clover) have finished flowering. [caption id="attachment_33904" align="aligncenter" width="650"] Oilseed rape[/caption] https://www.sciencedirect.com/science/article/pii/S0167880924005735?via=ihub Gardens and pollinators. A study In the Boston area of the US has revealed that small gardens with a diverse range of plants are important to pollinators.  The researchers first used Google Street View to identify and categorise some 86,000 front gardens (or yards, in their terminology) across the area - ranging from lawns to diverse flower gardens. They then visited 500+ of these gardens when the plants were flowering [in 2021], identifying and documenting the plants in each.   The found that : Whilst the higher income areas tended to have more cultivated flower gardens, these gardens were home fewer wild flower (weed) species. Small gardens often had the richest diversity of plants in flower as compared to those with lawns. The authors of the study conclude “Dense urban areas are a promising target for pollinator conservation.” Detail of this study can be found here : https://www.sciencedirect.com/science/article/abs/pii/S0169204624002706?via=ihub  

Gardens help out The blog has reported on several occasions on the problems bees, bumblebees and other insect pollinators face.  Now research by the Univeristy of Bristol has demonstrated the importance of gardens and urban areas to many farmland pollinators.  At certain times of years, such as early Spring and late Summer,, rural pollinators experience limited supply of nectar.   Somewhat surprisingly, a large percentage of UK farmland is within a mile of a garden, and at times of scarcity gardens can make good the lack of nectar [and pollen].  Indeed, the Bristol research (by Dr T Timberlake and colleagues) indicates that gardens can provide between 50 and 95% of the nectar during these 'lean times'.  Whilst gardens provide a relatively small amount of nectar in rural areas, nevertheless the continuity of the supply makes its contribution  particularly valuable. Full details of this investigation are reported here : https://royalsocietypublishing.org/doi/10.1098/rspb.2024.1523 Sunflowers to help bumblebees ? One of the issues that bumblebees face is infection by the parasite Crithidia bombi.  It lives in the gut of the bee. The parasite passes from host to host as cysts in faeces.  The parasites develop in the digestive tract, interacting with the intestinal lining using a flagellum.  Infection with this parasite seems to affect the bee's ability to learn and they struggle to recognise nectar-rich flowers, and consequently are at risk of starvation. Recent research has shown that if bumblebees are offered sunflower pollen to feed upon, then the Crithidia infection is significantly reduced. As bumblebees are often used in commercial glassshouses, it could be that if sunflower pollen was offered within this 'closed' environment then the incidence of Crithidia infection could be controlled.  The sunflower pollen does not have to be 'fresh', indeed stored, frozen pollen is effective.  A 1:1 mixture of sunflower and wildflower pollen also gives the desired 'medicinal effect', and ensures the bees are receiving enough protein and sodium from this supplement. Full details of this investigation are reported here : https://academic.oup.com/jee/article/116/5/1939/7234927        

Last week's woodlands’ blog talked about the fall in insect numbers across the UK.  This is not just a UK problem, it is far more widespread.  Insects,  bees and bumblebees as pollinators aside,  are important in ecosystems;  there are armies of other insects that are providing ‘services’ for us. When a tree dies in a woodland, bacteria and fungi are important agents in the decay of the tree and the recycling of elements, but they are assisted by beetles. If the dead tree was a veteran, during its lifetime it will have provided  a variety of micro-habitats.  Holes and crevices would have been used by bats,  birds,  insects etc.  Now, the the decaying wood will be support different organisms, from microbes to larger fungi, such as bracket fungi that can erupt from surface of the dead tree.   As the wood decays,  the material may become a ‘home’ for saproxylic beetles. For example, Stag beetle larvae feed on decaying wood (building up fat reserves, which the adults later rely on. it adds humus and fertility to the soil as its nutrients are released. Though bees and bumblebees (members of the order Hymenoptera) are important as pollinators (of many fruit and crop plants, so are the hoverflies key to  the pollination of many wild flowers.  Hoverflies belong to a different group of insects - the Diptera. There are several thousand hoverfly species spread across the world. They are found on every continent with the exception of Antarctica.  Work by Dr. Wotton and his team at Exeter University suggests they are situations where hoverflies may be more effective pollinators than bees and bumblebees, and the role of hoverflies in crop pollination may have been under-estimated.  Hoverflies can carry pollen over considerable distances, and may  visit isolated plants.  The common drone fly (Eristalis tenax) has been known to travel some 100km and carry the pollen of eight plant species.  Hoverflies (or Syrphidae) are also known to migrate over considerable distances.  The female marmalade hoverfly can migrate from Scandinavia to Spain and North Africa, migrating in the autumn to lay their eggs.  In the following Spring, succeeding generations migrate north again.  Some American hoverflies are known to migrate from Canada to the southern states. Insects are not just important in terms of facilitating decay or aiding pollination, some are involved in seed dispersal.  Scientists at Kobe University studied the dispersal of seeds from the fruit of the silver dragon plant.  Using  time lapse photography techniques, they watched to see which animals feed on the plant’s fruit at night. Whilst crickets (order : Orthoptera) ate much of the fruit, earwigs (order : Dermaptera) and woodlice (not insects, but terrestrial crustaceans) also consumed significant amounts of the tiny seeds of the fruit.  Further work demonstrated that many of the seeds survived the passage through the gut of these animals.  So apart from being seed predators, small invertebrates may also help their dispersal, depositing them away from the parent plant. Woodlice are interesting land based crustaceans that generally feed on dead and decaying plant material, helping in the recycling of nutrients. Further examples of the importance of insects in nature can be seen in fig production.  The fig wasp 'gives its life' in the process of pollinating the fig, in return the fig provides a safe ‘nursery’ for the young on the wasp, seed the woodland blog on the fig.  There are many types of fig and each has its own wasp, to ensure successful pollination.  Full details of the life cycle of fig wasps can be followed here.  The association between the wasps and figs is an example of mutualism. This co-dependence probably had its origin some seventy million years ago, and the wasps and figs have co-evolved since then. .

Though some insects are problematic in that they are carriers of disease (for example, mosquitos and malaria, ticks and Lyme disease); it is nevertheless true that without insects food chains and ecological systems would collapse.  Insects act as  pollinators not just of garden flowers, but of crops,  natural pest control agents (ladybirds eat aphids), Decomposers, breaking down waste products of other animals, remains of dead plants and animals (dung beetles). Their activity ensures the recycling of nutrients in complex biogeochemical cycles. However, as the woodlands’ blog has reported previously, insects (like so many wildlife species) are under threat.  They are in decline due to loss and damage of habitats,  climate change,  pollution and  pesticide use. The decline in insect numbers (in the UK) is ‘monitored’ through BUGLIFE and Kent Wildlife Trust.  Each year a survey is undertaken using the ‘splatometer technique’, in which motorists are asked to record the number of flying insects (e.g. moths, flies, aphids, bees and flying beetles) that are squashed on their front number plate (after a journey).  The length of the journey is recorded, a photo taken and count details uploaded via the BUGLIFE APP, the app includes a tutorial and some safety advice.  Comparing this year’s results of over 6000 journeys with those gathered in 2004 (by the RSPB, who used the same method) reveals a dramatic fall in flying insect numbers.   London, for example, showed a dramatic fall in numbers of 91%.  The fall across England was 83%, Wales saw a 79% drop and Scotland a 76% fall.   Whilst figures for Northern Ireland were limited they suggest a 54% decline. [caption id="attachment_21589" align="alignleft" width="300"] bumblebees favour teasels[/caption] Insects [and other wildlife species] can be helped by: Creating larger areas of natural habitats (many have been lost to roads, agriculture, urban expansion) Creating wildlife corridors to join up similiar habitats/ecosystems throughout the landscape Creating wild flower ‘meadows’ by road sides, verges etc Reducing the use of pesticides and other chemicals which have significant effects on wildlife.  The effect of neonicotinoids on bees and bumblebees is well documented.       

The period since WW2 has seen urban areas and, indeed farms, expand across the UK. The number of places where wildlife can thrive has been eroded.  Gardens and lawns have been changed to provide parking for cars, lawns are mowed and ‘weed-killered’, or worst still replaced with artificial grass so there is not a weed in sight.  Fortunately there are now initiatives like No Mow May that promote the growing of wild flowers in lawns and public spaces, like roadsides and verges.  Many common weeds are simply wildflowers by another name. Wild flowers / weeds (like dandelions, ragworts, clovers) are a lifeline for bees and bumblebees - who are facing so many threats [pesticides, habitat loss, invasive species] so adequate food is important. The flowers of these wild flowers / weeds offer food for a wide range of endangered bees, and at times when other resources are limited.  Dandelions, for example, offer an abundant source of nectar and pollen for bees & bumblebees when other options are limited - especially in urban settings. They produce their flowers (and therefore nectar and pollen) from early Spring right through to the onset of Winter. Recent studies have shown that the diet of bees has changed over the years.   In the past, the bees were able to forage and collect pollen and nectar from a wide variety of plants but with the loss of ‘natural’ wild areas their diet is now often dominated by brambles, clover and dandelions.  In the case of dandelions, their simple, open flowers makes for ease of collection.  They are visited by honey bees, bumblebees and carder bees.   Some studies have indicated that dandelion pollen, whilst it is rich in the amino acid proline,  has low levels or lacks certain amino acids (such as valine and isoleucine).  Bees need the same ten essential amino acids as us.  Without a supply of these particular amino acids, the development and growth of bees is impaired, as is their disease resistance and ability to raise the brood.  So, it is important to find ways to offer our pollinators a range of plants / pollen to provide all their essential nutrients. interesting related papers Food for Pollinators: Quantifying the Nectar and Pollen Resources of Urban Flower Meadows: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158117 Shifts in honeybee foraging reveal historical changes in floral resources: https://www.nature.com/articles/s42003-020-01562-4

The diet of bees has changed over the years.   In the past, bees were able to forage and collect pollen and nectar from a variety of plants.  With the spread of highly mechanised agriculture, increasing urbanisation and road network - now their options are somewhat limited.  Large fields of monocultures, for example, of oil seed rape are now common. Whilst oil seed rape is a good source for foraging bees and bumblebees, they need to collect nectar and pollen from a variety of sources so that they get a range of nutrients, such as the essential amino acids.  Without these particular amino acids, the growth and development of bees is affected, as is their resistance to disease and their ability to raise the brood.  It is important that our pollinators are able to find a range of plants / pollen to provide all their nutrients. Whilst wild flowers [aka weeds], like dandelions, ragworts, and clovers are a lifeline for bees and bumblebees, recent research at the University of East Anglia has shown that woodlands can offer important habitats for bees, isuch as the leaf canopy.  The research team studied 15 woodland sites in agricultural areas across Norfolk (in Spring).  Within the woodlands, they looked at the bee activity in  the understorey  the woodland edge  and at different levels in the tree canopy.   They found that bees were active high up in the sunlit tree canopy, and their activity was particularly high near flowering sycamore trees.  Red tailed bumblebees (Bombus lapidarius) were busier in the canopies than elsewhere.  The understorey and woodland edges were also significant contributors to bee activity.  This study emphasises the importance of woodland habitats for the wild bee community.  

On the Red List! The capercaillie is threatened.  Its numbers in Scotland have roughly halved (between 2010 and 2020).  It was once widespread, but now it is found in the pine forests of the Highlands - notably the Cairngorms National Park.  It is a red listed species. The decline in numbers is associated with poor breeding success, poor weather in early summer when the chicks are developing, another problem is predation by species such as the pine marten, foxes and crows.  The Game and Wildlife Conservation Centre (GWCT) has identified another issue that these birds face - namely collisions with deer fences.     These fences are created to keep deer out of particular areas.  However, when the capercaillie (and black grouse) impact on these fences, they are injured or killed.  Marking these fences, reduces the number of collisions but does not stop them.  Unmarked fences are still killing adult birds.  Marking of these fences or their removal would help with the survival of the capercaillie, though removal would  mean trees and shrubs would be unprotected from deer. Mosquitoes! There are some 36 different species of mosquitoes to be found in the UK, which  are generally harmless (though they bite).  But that may change.  With longer and warmer summers, the UK may become a venue for other species such as the tiger mosquito.   This insect has been found in ‘traps’ (monitored by the UK Health Security Agency) at ports and rail terminals.  This insect is known to transmit various diseases, such as dengue fever.  The mosquito was found in Italy in 1990 and it is spreading on the continent. A species of Culex has also been found in some areas of the Thames estuary - which can spread the West Nile Virus. This virus can result in flu-like symptoms.  Outbreaks have been been mainly in the warmer areas of the Mediterranean, but with climate change and the potential for very hot summers here - vigilance will be needed. Floral defences. Many flowers release a distinctive scent.  The scent serves to attract pollinators like bees and butterflies, or  it may ward off pests that would feed upon the plant.. Many of the chemicals that contribute to scents are terpenes.  Recent research has investigated how these chemicals can affect the growth and development of butterflies - using painted lady butterflies.  These butterflies feed on a wide range of plants and hence are exposed to a variety of scents / terpenes. For these experiments, the researcher (at the University of Centra Florida) used four common floral terpenes  Limonene :  which has a fresh, citrus like smell Linalool. : has a floral scent, reminiscent of lavender Cineole : has a camphor-like smell, slightly medicinal contributes to eucalyptus oil. β caryophyllene : this has a spicy / woody fragrance. Different amounts of these terpenes were fed to caterpillars of the painted lady butterfly, and the subsequent development of the caterpillars was monitored and the size of the adults recorded.  The experiment was also conducted at different temperatures.  Temperature affects scent release by flowers. Higher levels of terpenes has significant affects on the survival of the caterpillars, especially when combined with the higher temperatures.  The caterpillars took longer to enter into pupation when given high levels of terpenes, though the size of the adults that emerged from pupation was unaffected.  If longer and warmer summers become more common, the combined effects of terpenes and heat could become important determinants of development. `

Tree survival and drought. Researchers at the University of California have been working on a method that helps predict whether forests / woodlands can survive periods of drought.  As climate change is altering patterns of snow and rainfall, so periods of drought are likely to become more common. Forests are important in terms of carbon sequestration, that is, they take up carbon dioxide from the air and convert it into sugars, starches etc that are stored in the leaves, branches, stems and roots.  However, in order to assimilate and convert carbon dioxide (in photosynthesis), trees (indeed all plants) need a supply of water.  When water is limited, trees need to make use of their reserve materials.  Just as we make use of body reserves of fat and glycogen when food / diet in inadequate. However, reserves can only sustain a tree for a finite period of time.  If drought persists, the tree reaches a ’tipping point’ and it will die.  The researchers studied a forest in the Sierra Nevada that experienced a period of drought between 2012 and 2015.   During this period, millions of trees died.  The team recorded rainfall, soil moisture and temperature in the forest AND the amount of carbon dioxide that the trees absorbed, and their reserve materials.  They found that the trees were able to maintain function / health after the onset of the drought but with the passing of time, the trees exhausted their reserves and were unable to use / convert carbon dioxide into food.  They had reached the tipping point and died.   The methodology of this study was called CARDAMON (carbon data assimilation with a model of carbon assimilation); it is hoped that it can be used to evolve strategies to enhance forest and woodland resilience in the face of climate change. Pollinators. [caption id="attachment_35902" align="aligncenter" width="675"] hoverfly[/caption] University researchers from the UK and Finland have been trying to determine the most effective pollinators of crop plants, like strawberries (and other fruits).  Plentiful and effective pollinators are needed to ensure a good harvest of the fruits. The researchers studied the pollinators at three strawberry farms through the (long) growing season for the fruit.  They adopted two approaches : They caught the insects that visited the strawberry flowers and analysed the pollen they carried in detail (pollen load and type). They also counted the number of flower visits by the different insects, (a quick way to identify key local pollinators). Many insects were identified, including :-  European drone fly :           Eristalis arbustorum Honeybee :                               Apis mellifera Levels drone fly :                   Eristalis abusivus Buff tailed bumblebee :     Bombus terrestris White tailed bumblebee :  Bombus lucorum Common drone fly :             Eristalis tenax Red tailed bumblebee :      Bombus lapidarius Early bumblebee :                Bombus pratorum Bent-shinned Morellia :   Morellia aenescens Hoverflies are true flies, that is, they belong to the order Diptera or true flies, as they have a pair of wings and a pair of halteres (balancing  / orienteering organs used when in flight). Several of the flies in the genus Eristalsis are known as Drone Flies (due to their resemblance to honey bee drones).  The larvae of Eristalis  species are commonly found in putrid / stagnant water and sometimes referred to as “rat-tailed maggots”. It was noted that pollinators also made use of the wild plants to supplement their diets, as strawberries alone cannot meet the nutritional needs of pollinators.  ‘Elsanta’ strawberries have a relatively low sucrose and protein content in both their nectar and pollen. The precise  order of importance of pollinators varied between farms.  Bee (Apis and Bombus) species  and hoverfly (Eristalis) emerged as key pollinators. The European drone fly was the most important pollinator at two of the three farms studied, evidence that hoverflies can be effective pollinators.  One farm had commercial hives of the honey bee but they were less significant than the activities of of the hoverflies and bumblebees. The abundance of a particular insect, coupled with its active period were /  are important determinants of pollinator importance.  Sawdust and plastics - a possible use?. Plastics represent a relatively new, but persistent and major form of pollution (on land, in the sea, indeed everywhere).  Whilst many plastic objects are instantly visible in the form of discarded bottles, fast food containers, many plastic pollutants are in the form of very small particles of plastics  - nano and microplastics.  The concern is that we and other organisms are taking these microscopic particles into our bodies from our food / drinking water. However, it is possible that plant materials may offer some ‘solutions’.  Water that contains micro and nano plastics can be filtered through sawdust that has been treated with tannic acid.   Tannic acid is large molecule, its molecular formula is C72H52O46 .  Tannic Acid is found in certain plant galls (swelling of trees caused by parasitic wasps) and in the twigs of certain trees, such as Chestnut and Oak.  The wood sawdust contains fibres of cellulose, combined with hemicelluloses and lignin.  Water can flow through this material by capillary action.  This plant-based filtration (known as bioCap) of plastic-laden water is capable of dealing with a wide range of nanoplastics (PVC, PET, polyethylene etc), and tests with mice suggest that the filtered water may be sufficiently free of plastic to pose little risk.