JAcross Europe, the red squirrel is recognised as an endangered species.  The U.K populations are at risk due due to :- Habitat loss Competition with Grey Squirrels The effects of the squirrel pox virus The last two are a result of the introduction of the grey squirrel from America in the 19th century. Red squirrels are at home in all types of woodland and may even be seen in parks and gardens, but they 'like' mixed conifer forests best.  Scotland is home to many of the U.K's red squirrels. The number of squirrels is quite small – estimates of their number vary, perhaps there are less than 300,000* across the whole of Britain.   The status of red squirrel populations is a matter of considerable interest. [caption id="attachment_42416" align="alignleft" width="300"] Screenshot[/caption]  In 2014, it was noticed that some members of the Scottish red squirrel populations had abnormal growths on their ears, snout and limbs. Further investigations found that the squirrels were suffering from leprosy.  Leprosy  is a bacterial infection,  caused by two different species of mycobacteria: Mycobacterium leprae and Mycobacterium lepromatosis.   The two types of  bacteria have slightly different distributions in the squirrel populations of the U.K.  Whilst leprosy in squirrels was first reported in 2014,  it is likely that the disease has been around in squirrel populations for much, much longer, probably hundreds of years. Profesor Verena Schünemann,  Christian Urban et al have studied bacterial DNA extracted from human skeletons, dating from 400 CE to 1400 CE with deformities associated with leprosy.   They 'reconstructed' the genetic makeup of mediaeval forms of the bacterium.  Leprosy was not uncommon across Europe in mediaeval times - indeed up to the sixteenth century.   Disease, in its many forms , was a common part of life -  dysentery, diphtheria, typhoid, smallpox, and plague meant that life expectancy was limited. The last indigenous case of leprosy in the UK dates back to 1798.  In humans, leprosy causes muscle and nerve damage, which lead to deformity, blindness and disability.   Interestingly, research by Dr. Sarah Inskip has revealed that a pre-Norman skull [found in Hoxne in Suffolk] had a leprosy strain related to a form known to affect squirrels.  The same strain has also been found in medieval scandinavian skeletons.  It is possible that the  trade in squirrel pelts (and meat) could have contributed to the spread of the disease. Strong trade connections with Denmark and Sweden were in full flow in the medieval period.  Squirrel fur was also used as a lining for fine clothes and squirrels were kept as pets by some. The historical spread of leprosy is not fully understood.  The disease may have passed from squirrels to humans or vice versa in historical times.  Further study of the microbes that cause this disease (and that in squirrels) will help determine how the disease is acquired and transmitted.    The risk to human health is low. (Even so, good hygiene should be followed during any contact with wild animals). Professor Anna Meredith  (University of Edinburgh) is researching into this disease in squirrels.   Further reading / articles: https://www.newscientist.com/article/mg14819991-200-virus-blamed-on-invading-squirrels/ https://www.science.org/doi/10.1126/science.aah3783 https://www.theguardian.com/science/2017/oct/25/medieval-love-of-squirrel-fur-may-have-helped-spread-leprosy-study-reveals https://www.sciencedaily.com/releases/2017/10/171025103109.htm

The terms veteran tree or ancient tree are often used. But what is a veteran? A veteran tree may be defined by a combination of factors: its age its size; its condition; its history; its position. Read more...

The fact that UK is an island has kept many potential pathogens and pests ‘at bay’.  However,  in recent times the growth volume of international trade has become a cause for concern.  Pests and pathogens can ‘hide’ in important plants and plant products (for example, timber that has not been debarked or suitably treated). The Great Spruce Bark Beetle is likely to have arrived here in wood that had not had its bark fully removed.  The beetle breeds under the bark of trees, creating tunnels resulting in the destruction of the cambium.  The cambium is a highly active tissue, producing new cells that will go on to form xylem and phloem tissue.  These tissues distribute nutrients and water around the tree.  With a damaged cambium, a tree is weakened and more susceptible to other pests or pathogens. In the case of the Great Spruce Bark Beetle, a bio-control measure was allowed; a natural predator of the bark beetle has been introduced (Rhizophagus grandis).  Consequently, the numbers of bark beetles have fallen.  Wherever the bark beetle goes, its predator sooner or later follows.  It is thought that its predator ‘finds’ the bark beetles due to the volatile chemicals released from the bark as a result of the beetles' burrowing activities. The U.K.’s control measures generally proceed by four steps : Try to prevents pests and pathogens arriving in the country eg. Inspection of plants etc at ports of entry If a foreign organism arrives then the authorities try to eradicate the pest / infected plants / trees, hopefully the organism does not become established If a pest or pathogen has become established then a containment policy is put in place If all of the above fail then the Forestry Commission and other bodies operate in a way that mitigates the effects of the pest or pathogen.   Phytophora ramorum is a disease of many plants that probably arrived here through the plant import trade.  It has persisted at a relatively low level for many years but from 2009 onwards it affected commercial stands of larch in South West England.  Felling of infected trees helps restrict the spread of this fungus-like pathogen; and a map is available to show where outbreaks of this disease have occurred. Clearly, these introduced species of pest / pathogen could significantly affect the make-up of our woodlands over the coming years, if diseases like acute oak decline / ash dieback are not controlled or contained.  Fortunately, the spread of disease-causing organisms and pests is monitored by both national and international organisations such as these : EU Plant Health Directive this requires nations to report new outbreaks or new pathogens, t the European Mediterranean Plant Protection Organisation is an intergovernmental organization responsible for cooperation in plant health within the Euro-Mediterranean region and  the International Plant Protection Convention, a plant health treaty signed by over 180 countries.  

The autumnal fall of leaves in deciduous trees is a well recognised event; their changing colours prior to being shed often make for spectacular displays - the New England Fall. Evergreens (with certain exceptions) do not undergo a similar loss of leaves but that is not to say that their leaves are forever green or permanent.  Indeed, each year, evergreens have a seasonal drop of their needle-shaped leaves, it is normal part of the tree’s cycle.  The leaves / needles of conifers have varying life spans; they are not a ‘permanent fixture’.  Many conifer needles will turn yellow then as they age, falling off the tree after one to several years. This change can be gradual or in some species quite rapid.  White Pines (Pinus strobus) typically retain their leaves for 2 to 3 years, whereas Scots Pines (Pinus sylvestris) usually retain their needles for three years. Larches, which are conifers (Larix sp) are somewhat unusual in that they shed their leaves every autumn.  The stress that a tree experiences through drought may result in more rapid browning and greater loss of leaves. Read more...

Phenology is about the observation of natural events, recording when things happen, for example, when horse chestnut and ash trees come into leaf, or when the first swifts or bumblebees are seen. These timings vary from year to year. Through the recording of natural events over many years, one can look for trends and see if they are correlated with changes in the weather or other phenomena. Recent studies by researchers at Rothampstead, the Centre for Ecology and Hydrology, and the British Trust for Ornithology suggest that a number of different phenologies are changing.   They looked at various insect and bird populations in a variety of different habitats (urban gardens, agricultural systems, sand dunes, grassland, woodlands etc).  The broad conclusion was there was a “trend towards earlier phenologies for UK bird, moth and butterfly species across habitat types” . For example, aphids (which breed rapidly and can adapt to changing temperature quite quickly) now take flight some 30 days earlier in the year than fifty years ago.   Such phenological changes have ‘knock on’ effects.  For example, the earlier arrival of aphids can affect potato crops.  Aphids spread plant viruses and young potato plants are more susceptible to viral disease than older, more mature plants. Read more...

Climate change means that we are likely to experience more extreme weather events from intense and prolonged rainfall to severe drought and heat.  The plants and trees of woodlands may experience periods of flooding, during which their roots may be deprived of oxygen (as the soil is waterlogged) and consequently - die.  Similarly trees and other plants may be subject to drought - resulting in the stunting of growth or even death.  It had been thought that most trees had roots that penetrated deep into the soil (in search of water and minerals) but the aftermath of the Great Storm of 1987 revealed that this was not the case for many types of tree.  The root systems of many trees are, in fact, relatively shallow - the root plate may only reach down some five to six feet. Read more...

Over the centuries, our woodlands have experienced (to a degree) a relatively stable environment - both in terms of climate and biological ‘incursions’.  There have been occasional ‘perturbations’ some climate or weather related - such as the Great Storm of 1987 and some biological such as Dutch Elm Disease in the 1970’s. Our woodlands have been managed largely on the basis of this stability - a relatively constant biological and physical environment.  However now, climate change is an established fact and the number of biological threats to our native flora and fauna has increased significantly in recent times.   Climate change has seen the advance of Spring and more ‘extreme weather’ [for example, drought, high winds] plus the large scale movement / importation of trees, timber and plants from many different parts of the world has lead to the introduction of various pathogens and pests.  Read more...

We come across tannins in various foods and drinks.   They contribute to the taste of a cup of tea, a mug of coffee or a glass of wine.  Tannins contribute an astringent taste - a sensation of “dryness” in the mouth. Tannins are molecules made by plants - they are complex polyphenols built from several phenolic molecules.   A phenol is  made from a hexagon-shaped carbon ring with one or more hydroxyl groups (-OH) attached to it (see diagram). They are generally water-soluble molecules and they can combine with proteins, cellulose, pectins etc.  Tannins are generally stored in the vacuole of plant cells (as are various oils, resins, crystals of calcium oxalate etc).  Collectively, these materials are sometimes referred to as ergastic substances. Read more...