This is a re-post of a blog from 2023, but this time with the new film by WoodlandsTV, in which April Windle [of the British Lichen Society] examines the role of the many complex chemicals found in Lichens. Lichens are plant-like organisms that are rather unusual in that they are an amalgam of two (or occasionally three) organisms : a fungus and algae (or cyanobacterium). They are symbiotic systems, where the partners in the association work together for mutual benefit.  The fungus makes up the bulk of the lichen's form (known as the thallus), it is a complex network of fungal threads (hyphae) that surround the algal cells.  The algae (green algae or cyanobacteria) are essential to the symbiosis as they can photosynthesise, capturing carbon dioxide and providing both partners with organic carbon compounds (often in the form of sugar alcohols). Lichens produce an amazing variety of chemicals - many are secondary metabolites.  It is thought that some of these may  have medical / pharmacological properties.  Some species  of lichen are brightly coloured because of the chemicals.. The colour may vary from a golden yellow to a deep red. The pigments responsible for these colours belong to the anthraquinones.  However, these insoluble, phenolic pigments can have toxic effects. To avoid harm by these pigments, the lichen exports* the pigment from the fungal component of the symbiosis. [caption id="attachment_39795" align="aligncenter" width="675"] Moss and lichen growing together[/caption] The pigment then accumulates / crystallises on the surface of the lichen. The layer of pigment crystals reflects harmful radiation in the form of ultra-violet light and also blue light, whilst still allowing enough light to pass through for photosynthesis by the algae / cyanobacteria. Exposure to ultra-violet light can damage DNA, inducing mutations.  The pigmentl layer is effectively a ‘sunscreen’ for the lichen. * Recent work at Imperial College and RBG, Kew has identified the genes responsible for pigment production, and the transport of the pigment out of the fungal tissue. In the past, certain lichen pigments were often used to dye clothing materials.    Parmelia saxatilis, also known as grey crottle, was used to dye wool for Harris Tweed.  This lichen is often found growing on tree trunks and gives a red / brown colour to the material. For more information on the various chemicals found in Lichens, see the WoodlandsTV film below : The Chemical, Medicinal and Biofluorescent Properties of Lichen. [embed]https://youtu.be/AEc263aQ1rQ?si=00FwDTH5LljetQ0A[/embed] Curious fact : Some specimens of the lichen Rhizocarpon geographicum are thought to have lived for thousands of years.  

In 2023 the forest fires in Western Canada were so extensive that they burnt 37 million acres of forest lands, which is ten times the total area of forestry in the UK.  The carbon emissions were so great that they alone had a carbon footprint bigger than every country apart from the US, China and India.  Canada does not include emissions from wildfires in its carbon budget so the impact of its forest fires is in addition to its industrial and domestic carbon footprint. Although the total area burnt the next year - in 2024 - was smaller, the 2024 fires were particularly intense and destroyed 50% of the buildings in the city of Jasper. Forest fires affected infrastructure so badly that tourists were excluded from the whole of Jasper National Park in Alberta for many weeks.  This new intensity can also destroy trees that have been growing for hundreds of years and may have survived many other other fires.  This would have been the case for the King Arthur tree in California which had been the 9th largest Giant Redwood in the world: this huge and ancient Sequoia was destroyed in the 2020 Castle Fire. It is uncertain what is causing these intense infernos beyond climate change, to which the fires are themselves contributing. Many people believe that allowing too much dry and dead wood to build up creates the conditions for particularly hot fires which will easily jump fire breaks and natural circuit breakers, such as rivers   It may be that the First Nations [as Canadians call the native peoples who inhabited the country for thousands of years before European settlers arrived] were better at managing the land and would have reduced the fuel load in the forests, and there would have been a greater variety of tree species. Another paradox is that when the National Park authorities are most effective at putting out fires this allows a greater fuel load to build up so that there can be fewer fires but much bigger ones. To counter this, some Canadian Park managers are deliberately starting fires which they believe will be controllable - this is evident in the forests next to Lake Minnewanka. These are done in the off-season when large conflagrations are unlikely. In the past, forestry companies tried to extinguish fires by using float planes, such as the Hawaii Martin Mars dropping water.  This was put in an air museum in August 2024. The seaplane's water deposits were less well-targeted than today's helicopter drops.   Nowadays, forest blazes are usually left to run their natural course and this can take a long time.  Sometimes a fire will continue smouldering underground and it can be 18 months before a forest fire is confirmed to be finished. In cases where buildings, main roads or railway lines are threatened there will often be efforts to extinguish the fire using helicopters.  Drones are also used to survey the progress of fires. One measure which might reduce the issue is to replant burnt-out areas with  species that occur naturally and are  less flammable and better as surviving such as Eucalyptus.  However, the hotter, drier summers are creating conditions where we are in a new age of more intense forest fires and the Canadians are adjusting as fast as they can.  This means short term measures such as evacuation plans and more firefighting equipment, as well as longer term plans such as working on a better mix of trees and combating climate change more widely.

An electric or hybrid car needs a rechargeable battery to power the electric motors of the vehicle. The batteries make use of oxides of lithium nickel manganese & cobalt. The battery of such vehicles makes up a significant portion of  the cost and  environmental impact  of an electric vehicle.  Growth in this market has created issues in securing ethical battery supply chains. The future supply of nickel, cobalt and lithium is problematical, presenting challenges both in environmental and geopolitical terms.  Much of the battery production is centred on China.  Mining of a metal such as Nickel generates significant quantities of carbon dioxide, which contributes to global warming.  The demand for Nickel is forecast to double. An alternative to traditional mining techniques for metallic ores is phyto-mining. This is possible where there is a significant quantity of the metal in the soil, and there is a plant that can take up and accumulate  the metal.  The absorption and accumulation of metals like Nickel, Cadmium and Copper is perhaps more problematic as they are toxic to many plants.  Worldwide some 450 different species can absorb and accumulate ‘toxic’ metals, growing in ‘poisoned’ or toxic soils, such as former mine workings.   Some of these plants are hyper-accumulators – noted for their ability to take up a metal to many times the level in the soil. In Albania, a project is underway to use a plant to ‘mine’ nickel.  The plant is a perennial herb with yellow flowers - Odontarrhena decipiens.  It is a member of the Brassica / cabbage family and is a hyperaccumulator.  It can take up into its stems and leaves about 2% of its dry weight as nickel.  The plant is being ‘farmed’ in Albania, where there are nickel-rich soils derived in part from the mineral Olivine.     Though olivine contains too little nickel for conventional mining, it has enough for hyper-accumulators to absorb and concentrate it.  When the olivine is ground up and spread on the field, it not only replenishes the soil with nickel [that the plants absorb] but it also reacts with carbon dioxide in the atmosphere locking the CO2 away.  This project is being developed by ‘Metalplant’ . Whether phytomining using this plant will prove to be a useful way of augmenting Nickel supplies remains to be seen.  

There are eleven thousand trees in Kew Gardens.  Each year, a few trees are lost due to natural causes, old age, disease etc.   In 2002, a drought resulted in the loss of  some 400 trees.  Such a prolonged dry spell is  likely to occur again and again as global temperatures rise, and climate change takes a hold. Modelling of future climate scenarios by Kew scientists suggests that towards the end of this century between a third and a half of Kew’s trees could be lost.  Trees like the English oak, beech, birch and holly could be vulnerable to warmer temperatures and extended dry spells.  There is a plan at Kew to replace gradually trees with species currently found in warmer areas, such the Mediterranean, Asia and Central America. Examples might include species such as the iberian alder, cherry hackberry and Montezuma’s pine.  Many of the plants in the gardens will survive, [including Kew’s ‘Old Lions’] as they were collected from in and around the Mediterranean; some of these date back to the victorian era or earlier. The ‘old lions’ of Kew are trees from the original grounds / garden that still survive. Examples include : Japanese pagoda tree (Styphnolobium japonica) Maidenhair tree (Ginkgo biloba) Oriental plane (Platanus orientalis) Caucasian elm (Zelkova carpinifolia) Black locust (Robinia pseudoacacia) The Caucasian elm dates from 1762, when an arboretum was planted.  It is thought that it might have been in a batch of plants from the Caucasus, planted in what is now the herbarium paddock.  In 1905, the height of the tree was recorded as 60 feet (18M), though they can grow to 100 feet.  A larger caucasian elm can be seen at  Tortworth. One species of oak that is common at Kew is the holly or holm oak (Quercus ilex).  This is a common, naturalised oak that was probably introduced into the country in the sixteenth century.  It is a hardy, slow growing tree and many new holm oaks were planted in 2008 to redefine the Syon Vista.  The wood of the tree is strong and, in the past, it was used in carts and farming equipment. Its acorns start off green in colour but turn a reddish brown; they are a tasty treat for pigs. The threat to Kew's trees is not unique, parks and urban spaces across the country need to plan for the future, to ensure that their trees can offer some resilience to changing weather patterns. Full details of Kew's planning here.  

Much has been written about the explosion of the UK deer population in recent times, and the damage to woodlands through their browsing activities.  However, the grey squirrelis associated with tree damage.  The grey squirrel is not just the 'cheeky chap' who steals the bird food in the garden, it is a serious pest.    The grey squirrel is a non-native species.  It was introduced in the 19th century.  The squirrels have spread across the country and have displaced the native red squirrel from many areas (either through competition or disease).  The grey squirrel's bark stripping activity now poses a threat to the sustainable management of woodlands. Gnawing of the bark means that they can get to the sweet, sap filled tissue (phloem) just beneath the bark. This tissue is responsible for the movement of sugars and other organic molecules around the plant (known as translocation). If the gnawing extends around the stem then the tree is ‘ringed’ [i.e a complete circle of bark and underlying tissue is removed]  then the tree us likely to die.  The squirrels tend to take bark from the main stem (and branches). The bark stripping may : Lead to the loss of particular tree species (for example, beech) Lead to the loss of insect / spider and fungal species associated with the loss of tree species, i.e. a loss of biodiversity allow fungal infection of the tree Reduce carbon capture Reduce the economic value of timber Act as a disincentive to creating new woodland for timber In order to reduce squirrel damage, it is important to Start inspecting for damage in late February as damage typically occurs in early Spring.  Examine the base of trees for damage. Look for ‘tester patches’ made by squirrels (to which they may well return later). Check young, broadleaf trees as they are particularly favoured by the squirrels.  Oak and beech are quite vulnerable to damage (see image of damaged beech trunk below). Recent research* at Bangor University has investigated the microbiome of the squirrel in relation to its bark stripping activity.  The microbiome of the gut refers to the various micro-organisms found with the intestines.  Analysis of bacterial DNA found in the colon of great (and red) squirrels revealed that grey squirrels had 'oxalobacter' bacteria in their colons.  These bacteria are able to 'release / access' calcium from the tree bark to the squirrels.  Calcium is an important nutrient in terms of bone building and is also involved in muscle contraction. had  a more diverse bacterial population in the colon. These findings may help explain why the grey squirrel 'outcompetes' the red squirrel.  Their more diverse gut microbiome may mean that they can access a greater range of resources. For example, grey squirrels can digest acorns, which red squirrels cannot;  this is possibly associated with tannin content of acorns. In order to reduce damage in a woodland, the number of grey squirrels may need to be managed.  This can be done though trapping or shooting.  Trapping is a legally acceptable and effective way of controlling grey squirrels in most situations. Grey squirrels can be trapped throughout the year though March to September is a good time as food is less abundant. Through autumn, berries, nuts and seeds [natural foods] are available so trapping is less successful.  Details of the various types of traps and their use / placement may be found at: https://greysquirrelcontrol.co.uk/trapping-method.php https://www.britishredsquirrel.org/wp-content/uploads/2016/07/Grey-Squirrel-Best-Practice.pdf https://basc.org.uk/pest-and-predator-control/grey-squirrel-control-with-live-capture-traps/ https://www.britishredsquirrel.org/wp-content/uploads/2016/09/Trapping-Protocol.pdf  https://bpca.org.uk/a-z-of-pest-advice/squirrel-control-how-to-get-rid-of-squirrels-bpca-a-z-of-pests-/188983 To go down the ‘shoot to kill’ route then there are a number of rules and regulations to observe.  Details may be found in the link below : http://www.britishredsquirrel.org/grey-squirrels/grey-control/ It is hoped that eventually a form of oral contraception will be developed, which will offer a non-lethal and humane means of population control. Full details of this research work may be found here

Stinging nettles grow in a wide range of natural habitats, river banks, swamps, meadows, wastelands, floodplains, disturbed areas and gardens. They are are particularly effective colonisers of disturbed, bare or ‘waste’ ground. They flourish in nitrogen-rich soils.  Their seeds can lie dormant in the soil for some five years (and can even survive soaking in salty water), plus they spread using their underground rhizomes. Nettles may not be the most friendly plants to us, as their leaves and stems are ‘armed’ with special ‘hairs’. The hair-like structures are termed trichomes and each trichome has a hollow tube-like structure. At the bottom of the tube is a swollen base, which is filled with a number of chemicals, (including histamine, serotonin, formic acid and acetylcholine). The tip of the tube is easily broken, leaving a sharp point that can penetrate the skin and deliver the ‘biochemical cocktail’. [caption id="attachment_7154" align="aligncenter" width="600"] Trichomes - loaded with their chemical 'cocktail'[/caption] [NB: there is a video on YouTube that shows this mechanism here.] This collection of chemicals gives the characteristic rash/inflammation of a nettle sting.  Nettles may be found near to dock leaves which, if crushed and rubbed where you have been stung by the nettle, may take away some of the pain. More detailed information on the chemistry of the 'chemicals' in the nettles can be found here.  The hairs / trichomes probably evolved as a defence mechanism to limit grazing by sheep, deer or rabbits. Despite their ‘weaponised hairs’, nettles are in fact very good for wildlife, particularly in urban / sub-urban areas.   This is also true in areas under intensive farming practices.  The spread of farming, urban sprawl, habitat fragmentation and pollution have all contributed to the loss of natural habitats (for plants and animals), and that’s without mentioning climate change. Stinging nettles are the food plant for the caterpillars of comma, painted lady, peacock, red admiral and small tortoiseshell butterflies. The presence of nettles in our gardens and urban areas has allowed these butterflies in. And it’s not just butterflies that rely on nettles. For example,  ladybirds often lay eggs on nettle leaves. This insect might be termed a “gardener’s friend” as it has a voracious appetite for aphids - greenflies and blackflies that suck the sap from plants, ravage the vegetables in our gardens / allotments, Some aphids spread plant viruses, for example, virus yellows on sugar beet. Having nettles in our gardens and near farms give ladybirds and other insects somewhere to shelter, ready to feast when the aphid population rises. Aphid populations can rise very quickly as females give birth to live young, without fertilisation. Nettles can be used to make tea, soup, flavour beer, wrap cheese (Cornish yarg) or make cloth.  Using nettle fibres to make fabric / clothing is a very old practice, dating back to the Bronze Age.  Nettles can also be used to dye fabric [caption id="attachment_34107" align="aligncenter" width="650"] stinging nettle[/caption]

Ragworts are a group of daisy-like flowers.  The flowers are actually composites, that is, they are made up of many smaller flowers held together in a structure called a capitulum.  The family of daisy-like flowers is known as the Asteraceae (previously called the Compositae).  There are several different species of ragworts, for example : Common Ragwort (Jacobaea vulgaris, previously Senecio jacobaea) Oxford Ragwort (Senecio squalidus)  Hoary Ragwort (Senecio erucifolis) Marsh Ragwort (Senecio aquaticus) Silver Ragwort (Senecio cineraria) Perhaps, the Common Ragwort and the Oxford Ragwort have attracted the most attention in recent times.  The story of the Oxford Ragwort is interesting. The plant is actually native to Sicily, growing on volcanic ash and scree.  It was grown in the Oxford Botanic garden around 1690.   After some years, it ‘escaped’ and could be seen growing around Oxford.  Later, with the advent of the railways, it was able to spread along the railway tracks and then across the country. The genetics of this plant and related species have been the subject of various research projects in recent years, and has resulted in the ‘reclassification’ of some ragwort species. However, it is the Common Ragwort (Jacobaea vulgaris, previously Senecio jacobaea) that has been the focus of much attention.  This is a native, biennial plant, but can be perennial. Its seeds are spread by wind and a single plant can produce thousands. Consequently, it can become a problem on waste land or other uncultivated areas. Ragwort may be seen in coppiced woodland,  particularly in the years immediately after cutting the coppice when there is lots of light and the ground flora 'comes alive'. The plant is a good food source for a wide range of insects and it is much 'loved' by pollinators.  Over a hundred insect species feed on its nectar  (bees, flies, moths and butterflies).  Not only is it a good source of nectar, it also provides a home and / or a food source for many invertebrate species.  Some insects feed on the ragwort exclusively.  [caption id="attachment_40185" align="alignleft" width="300"] Cinnabar moth caterpillar[/caption] One species that is particularly associated with this plant is the cinnabar moth, whose status is described as ‘common and widespread, but rapidly declining”.  The caterpillars are distinctive with yellow and black stripes. They feed on the ragwort absorbing its alkaloids, which make the caterpillars distasteful to predators.   Alkaloids are organic compounds produced by plants and many of them have potent medical uses - such as quinine (for malaria) or morphine (pain relief).  Most alkaloids have a bitter taste.  Many alkaloids are toxic (for example, atropine from the nightshade family of plants).  The alkaloids present in ragwort can make it a problem when present in fields / areas grazed by horses or cattle, though it is not usually a problem in gardens.  Horses do not normally eat ragwort due to its bitter tasting alkaloids but if consumed in any quantity then the alkaloids can cause liver damage (a form of cirrhosis). [caption id="attachment_40489" align="alignleft" width="300"] Tweet from Prof Goulson[/caption] Ragwort poisoning is relatively uncommon and may arise through feeding with hay that contains dried ragwort.  In U.K., the common ragwort is classed as an injurious weed under the provisions of the Weeds Act 1959, and there is the Ragwort Control Act 2003.  The latter provides for a code of practice relating to ragwort.  Removing common ragwort from an area is not without its problems.  Sometimes, other species are ‘identified’ as ragwort and sprayed with weedkiller.       Friends of the Earth have produced a ‘briefing’, which notes that Ragwort has been blamed for animal deaths which are unproven Scare stories have been based on poor or irrelevant statistics, and biased surveys Ragwort has been falsely labelled as a threat to human health / the countryside As a result, unnecessary measures have been used to control ragwort (in nature reserves or areas like the New Forest, and indeed roadside verges). The briefing, entitled  “Ragwort: problem plant or scapegoat?” which can be accessed here offers a number of solutions to the ‘ragwort problem’ Further information about controlling ragwort is available on WoodlandsTV - see below: [embed]https://youtu.be/esfLW0nIvNo?si=DQ2Uokq7U1pAJYMZ[/embed]

The honey bee, Apis mellifera, stores food in the form of bee bread. Bee bread is formed through the fermentation of a mixture of pollen, nectar and bee saliva.   It is 'inoculated' with a range of bacteria and yeasts that ferment the material after storage in the comb cells of a hive.  Bee bread is the chief protein resource for bees, particularly for the feeding of larvae [and adults].  As it is a nutrient-rich material, it ‘supports’ various microorganisms, despite its acidic nature and low water content. Bee bread is also coated with propolis.  Propolis (sometimes called ‘bee glue’) is a resinous substance collected by bees from tree bark and leaf buds. This resin is ‘chewed’, mixed with salivary enzymes and the partially digested material is mixed with beeswax.  It is an antimicrobial substance.  It is used by bees to seal holes in their honeycombs and help in the construction of the hive. The very nature of bee bread and the coating of propolis create a ‘challenging environment’ for microbes to grow and survive.   However, despite the ‘unwelcoming’ nature of bee bread, several species of fungi and bacteria form a microbiome within a hive, and are thought to play an rôle in the life of the bees. Recent studies have revealed that the fungus Aspergillus flavus is well adapted to survive in bee colonies.  A strain extracted from a hive was found not only tolerate low pH (which other strains of the fungus could not cope with) but could also deal with the low water content of bee bread, and with the propolis - which is thought to have anti-fungal properties.  Further work demonstrated that this strain of the fungus had mutations that allowed it to develop within the ‘bee bread environment’.  That this fungus can live with the bees suggests that there might be some form of mutual benefit to both fungus and bee, but the relationship (if there is one) is not as yet understood. Full details of this study can be found here