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        

Bees and light Honey bees need to sleep.  Unlike us, they do not sleep for long periods but they take ‘naps’ during the day and the night - within the hive where it is dark.   If the hive becomes over heated, then bees will move outside the hive and beat their wings to fan cooler air into the hive.  If the bees are exposed to artificial light during the night then there is evidence that their ability to perform the ‘waggle dance’ is impaired.   The dance is important as it tells other bees where to source pollen and nectar.   Cooling of the hive may become increasingly necessary with climate warming (and heat spells), which in turn might expose bees to artificial light at night.  Hives might need to placed away from road sides (hence car lights) and street lights.  An ancient pine. The Wollemi pine is rightly described as a living fossil.  It is a plant that has remained unchanged for millions of years.    An almost identical fossil form dates to the Cretaceous period , some 145 million to 66 million years ago.  Whilst the trees were abundant some 8 to 6 million years ago, now only 60 trees exist in the wild (in a canyon northwest of Sydney) and they are at risk of wild fires. The population of these pines has dwindled as the climate in Australia became drier and warmer.   The genetic make-up of the species has recently been analysed.  It turns out that the tree's 26 chromosomes contain some 12.2 billion base pairs; by comparison, the human genome has 3.4 billion base pairs.  The research also indicated there was very limited genetic diversity within the Wollemi pine population.  The existing trees appear to  have abandoned sexual reproduction, and now reproduce mainly by cloning, suckers emerge from the base of a tree and then grow on to become ‘new’ trees. Whether this remnant population of the Wollemi pine will survive ongoing climate change (and increasing risk of fire) remains to be seen.  The wollemi pine also appears to be susceptible to disease, in particular to Phytophthora cinnamomi, a pathogenic water mold that causes dieback.  

Flowers of the woodland floor. Some woodland flowers enjoy the dappled light of the woodland floor beneath the canopy.  They grow in relatively shady, cool and damp conditions in the humus-rich soils.  Polish scientists at the Nicolaus Copernicus University have been studying four species that often grow together in European woodlands - namely Wood anemone Yellow anemone Lily of the valley Common may lily These are perennial plants that ‘come to life’ in Spring, producing a carpet  of flowers across the woodland floor.  However, as much as they share a liking for the shady, cool and moist conditions found there, they differ in their sensitivity / tolerance to rainfall / moisture levels in the summer months: which may change their distribution as summers become warmer and longer.  The team modelled various warming scenarios which suggested that the ranges of these species may change / contract with hotter and drier summers.  The common may lily is one that may be particularly affected and no longer share the same range or woodlands as the others studied.  If climate change takes a hold, it may be that ‘assisted migration’ may be needed to help such plants to find suitable ‘climatic refugia’. more on plant migration ...... With climate change, both plants and animals need to adapt.  With increasing warmth, many species may ‘need’ to move towards cooler latitudes.  Whilst many animals are mobile, they may be able [over time] to access new suitable areas, plants on the other hand are dependent on the dispersal of their fruits / seeds.  Fruit and seed dispersal may involve various animals, including birds.  If the birds are resident or non-migrating species, then it is probable that they will only disperse seeds over relatively short distances.   Migratory birds however travel great distances but often in the wrong direction.  Many birds that migrate at the end of the summer, travel south to warmer climes.  Work at the University of Exeter has studied a number of woodlands across Europe and bird species that feed on the fruits of 81 plants species (and help disperse their seeds).  They found that only about a third of the plants had fruits (seeds) that might be dispersed northwards by birds.  To benefit from this northward dispersal, the plants needed to either have a very long fruiting period (eg.holly, juniper) or a very late fruiting period (eg. Ivy). Full details of this study here Food production and food waste. As Sir David Attenborough has pointed out in a recent episode of Planet Earth III, producing food to feed the world comes at significant environmental cost.  Natural ecosystems are often burned (forests) or drained (peatlands) and then turned over to agriculture to produce crops or farm animals. The forests of the Amazon have been significantly affected by burning and logging,  with the concomitant loss of biodiversity.  But they are not alone. In Mexico, forests are being lost as the land is being turned over to avocado production.  Mexico’s neighbour, the USA has a voracious appetite for this fruit.  The forests are being turned into ‘avocado orchards’.  Avocado trees are ‘thirsty’, they need a generous supply of water.  They consume much more water than the natural species [eg. oyamel), so that natural aquifers are being depleted.  This affects local farmers growing crops such as tomatoes and corn. One particularly sad aspect of food production is that much of the food is wasted. Some is lost between harvest and reaching the retail sector, and then more is ‘lost’ in the home. Food may not be used, or not used in time so it starts to rot, become rancid etc.  A lot of food goes to land fill, where it may generate methane - a potent greenhouse gas. Sprouting sequoias. In recent times, there have been many images of the fires ravaging the forests of the west coast of the States.  Many thousands of hectares and millions of trees have been lost, including many of the giant redwoods.  However, recent studies have found that some of the burned Sequoias are producing new growth.  They are sprouting from roots and trunks, from dormant buds that have lain hidden under the thick bark for decades, this despite the loss of the canopies of the trees.  To fuel this growth, the trees are using reserve materials that have been stored for 50+ years.

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.  

Trees for a longer life? Researchers from US Forest Service has completed a survey of tree planting in Portland, Oregon and concluded that the more tres are planted in an area, the longer people live. The Portland “Friends of Trees” have planted some 50,000 oaks, dogwoods and other trees around the city over the last thirty years.  After adjusting for factors such as race, income, age and education, the team found that where more trees had been been planted, fewer people died.    This was true for all areas - wealthy or less so. Furthermore, as the trees aged, the mortality rates of the people nearby went down.  Trees generally improve air quality and moderate extreme high temperatures.  A recent report in the medical journal The Lancet suggested that many of the premature deaths from the 2015 heat wave in Europe could have been avoided with 30 percent more tree cover. Birds in decline. UK bird populations are in decline.  Much of the decline occurred in the 1970’s and 80’s, and was particularly noticeable in populations of farmland and woodland birds.  However, the losses have continued in recent times, with a 5% decline between 2015 and 2020. Again, woodland birds have fared poorly with a 12% decline in this period.   The steepest decline in population numbers are seen in species such the Tree Sparrow, Willow Tit, Lesser Spotted Woodpecker and Nightingale.  These have all declined by 90% or more since the late 1960’s. The Turtle Dove shows the biggest decline of any species. Habitat loss is thought to be the main driver of population decline for many species, but oil and plastic pollution are also factors, as is disease - such as trichomonasis and avian flu  Certain species typically associated with urban areas / habitats (Swift, House Martin, Starling and House Sparrow) are also declining. Predation by cats might be a factor, the Mammal Society estimates that cats in the UK catch some 92 million prey items over Spring and Summer, of which around 27 million are birds. Disease such as avian malaria is another factor, one study found 74% of sparrows were infected with the parasite Plasmodium relictum; the changing nature of urban gardens may also be a consideration.  Bees and sunflower pollen grains Bees and bumblebees are struggling with various parasites /infections.  One parasite is the gut pathogen Crithidia bombi.  This is known to affect the ability of bumblebees to create a successful colony. Previous studies have indicated that the the gut microbiome of the bees can help protect against infection by this parasite.  Now a study at the University of Massachusetts Amherst has found that sunflower pollen can help bees resist infection.  It was not known why sunflower pollen was effective, it could be that the shape of the pollen grains was important or the chemical makeup within the grains, or a combination of the two. To test the ‘anti-parasitic nature of the pollen’, an experiment was set up so that some bees received the outer shell of the sunflower pollen (the sculptured exine), whilst another group received the materials from the centre of the pollen grains (but no outer coverings), and a third group received whole pollen.   Bees that received whole pollen grains or just the spiny shells had far less of the parasite in their gut compared to those eating the ‘soft centres’ .  The pollen grains and pollen shells reduced infection by 80 to 90+%.  So it is the spiny shape of the pollen grains that is important in reducing infection in the bees.  'Physical removal' of pathogens is known in other animals, for example, great apes infected with certain nematodes or tapeworms will consume bristly leaves.   These 'irritate' the gut and increase the expulsion of the parasites.

Earlier flowering times. A survey has shown that plants are flowering earlier in the year.  Cambridge University researchers compared the dates of flowering of some four hundred plus species before and after 1986. They found that plants are now flowering roughly one month earlier.  More recent decades have been associated with rising air temperatures. This change in flowering time may have profound consequences for the plants.  The vast majority of plants are dependent on pollinating insects (bees, bumblebees, hoverflies) to set seed and complete their life cycles.  By flowering early their cycle, plants may not match up  with the activities of their pollinators. They may flower but their pollinators bee ‘missing’. Their pollinators need to emerge from their overwintering stage earlier. Earlier flowering may not matter for those plants that are visited by several pollinators but for those that are dependent on one or two specific visitors - it may critical.  For example, Sainfoin.  Sainfoin is host to a particular (solitary) bee Melitta dimidiata (remote image here).   It is a monolectic bee; i.e., a bee that collects food (nectar and pollen) from only one species of flower - the sainfoin.  If the sainfoin flowers earlier in the year and the bee does not match the shift in flowering, then the bee has a problem. Work on the effects of climate change on pollinators has been somewhat limited to date, but studies in Japan suggest that bees / bumblebees are somewhat behind plants in their response to environmental changes. Bee and bumblebee news. Recent research data provide evidence that (buff tailed) bumblebees are not able to detect or avoid concentrations of pesticides [imidacloprid, thiamethoxam, clothianidin, or sulfoxaflor], as used ‘on the farm’ - from signals sent by their mouthparts. The mouthparts are covered with tiny hairs and these hairs have ‘pores’ in them. Chemicals pass through these ‘pores’ to sensory cells; this is how the bee tastes and smells. It seems likely that the bumblebees are at considerable risk of consuming pesticides in their search for nectar when visiting pesticide-treated crops. [caption id="attachment_19675" align="alignleft" width="300"] Bumbles foraging in artichoke[/caption] Another agrochemical,  Roundup,  has been found to affect the learning and memory of bumblebees. Roundup, which contains glyphosate, affects their ability to learn and memorise connections between colour and taste.  Impaired colour vision is likely to affect the foraging and nesting success of the bees.  The research was conducted in Finland by researchers at the University of Turku. In yet another concerning study, researchers at the University of Maryland have found that the life span of laboratory-raised honey bees has reduced considerably.    Five decades ago, the lifespan for a worker honeybee (Apis mellifera) under controlled laboratory conditions was about 34 days. Now it is some 17/ 18 days - according the report in Nature.  The study also reviewed the scientific literature [from the 1970s to now] and noted a trend in the life span of bees.   Shortened worker bee lifespan has implications for colony health and survivorship.  The work at the University of Maryland is ongoing. Methane release. Ghost forests are found in coastal areas.  As a consequence of climate change, sea water has ‘invaded’ low laying areas and trees have died. The dead trees are sometimes referred to as ‘snags.  A  number of woodland / forest communities along the eastern coast of the United States have been affected.  Recent work by North Carolina State University has shown that these ghost forests release methane.  The methane is generated by bacteria in the soil but then ‘escapes’ by means of the ‘snags’.  As it passes through the wood of the ‘snags’, microbes may consume and alter the methane.   As methane is a potent greenhouse gas, understanding the nature and extent of these methane emissions from ‘ghost forests’ is important. Tree rings The study of tree rings has been invaluable in dating many historic objects ./ archaeological sites.  Now, it seems that they could play a role in estimating the amount of carbon that trees are actually absorbing (carbon sequestration), if woodland / forest inventories are coupled with core samples of the trees. The measurement of the annual rings from such cores could create a record of ‘tree growth across space and time’, yielding a more accurate estimate of the amount of carbon being taken up by woodland and forests. Forests, soils and oceans are major ‘carbon sinks’.

Electric bees ? Both bumblebees and flowers carry an electric charge.  Flowers have a weak negative charge, whilst the bees have a positive charge.  The attraction between these two opposing electric fields may help the bees sense flowers.  The electric charge of a bee may even stimulate a flower to release a burst of scent, aka volatile organic compounds.  This was true for petunias, but not snapdragons.  When a bee has visited a flower, the negative charge is briefly lost - maybe a signal to tell other bbees not to visit? Other work by Bristol University has indicated that synthetic fertilisers and pesticide can interfere with a flower’s electric charge for some time after spraying, and that this can modify the foraging of bumblebees. "Black bees" The black bee, Apis mellifera mellifera, faces a number of threats like the domestic honey bee.  It is also known as the European Dark Bee or the Black German Bee. It has been present since the retreat of the last Ice Age, but its distribution has become restricted as a result of habitat loss, parasitism by Varroa mites and viruses. The black bee can be distinguished from other honey bees by its stocky body and sparse abdominal hair (which is brown), and overall dark coloration - so they appear black or dark brown. Recent research (using DNA analysis) has shown that black honeybees can be found in many locations in Ireland and are not extinct, as previously suggested  Black bees are noted for their longevity and hardiness (ability to cope with winter temperatures); it is possible that if winters become shorter / milder that this change may not favour black bees. Weird weeds? It seems that our gardens may be home to ‘new’ or unusual species of plants.   The Royal Horticultural Society would like gardeners to report on interesting ‘weeds’ that might find as they could be rare plants or plants growing in unusual places / areas.  You are asked to take photographs of anything that you find interesting, and upload the images to iNaturalist. Reporting on unusual plants is not the only thing that the RHS is interested in. There are other garden projects that one can contribute to, for example, reporting sightings of garden pests such as the berberis sawfly, cellar slug, hemerocallis gall midge, lily beetle, rosemary beetle and spittlebug. Mycorrhizal networks. A common mycorrhizal network (CMN) is when fungal hyphae connect the roots of many plants (either of the same or different species) below ground.  They have attracted considerable attention in recent times (woodland wide webs), with claims, for example, that resources are transferred through CMNs to increase seedling performance and mature trees send resources / defence signals to offspring etc.  However, a recent report in Nature has suggested that there is a ‘bias’ towards citing the positive effects of CMNs and that, to date, knowledge of common mycorrhizal networks is limited.