A plant growing in the wrong place is sometimes described as a weed, but it can be more than just an inconvenience.  Plants in the wrong place can have a devastating effect on ecosystems, dramatically reducing biodiversity.  The same is true for certain animals - those that have 'traveled' from their natural habitats to 'foreign areas’ where they have no natural predators to keep their numbers in check.  Foreign or alien species are sometimes introduced to an area in the belief that they will solve local problems with pests or over-population of a native species.   A classic example of this is the cane toad.  Native to  parts of central and South America, the cane toad is preyed upon by a variety of animals such as caimans, snakes, eels and some fish species.  It was introduced into sugar plantations in various parts of the world to control beetles that were damaging sugar cane crops. Since this was a successful strategy in Puerto Rico, the toad was introduced elsewhere, notably Australia.  Just over a hundred toads were released in Queensland in 1935, with more released in 1937.  Unfortunately the toad did not effectively control the grey-backed cane beetles (the intended target), and they found other things to eat.  Their numbers grew exponentially and they spread into other areas, such as the Northern Territory and New South Wales.  These poisonous toads have significantly reduced biodiversity particularly affecting native amphibians and reptiles. Sometimes foreign species are introduced as ornamental plants or 'exotics'. During the Victorian period many plant species were brought to the UK for country estates.  Rhododendrons that were collected across Asia and the Himalayas became popular in parks and gardens.  However, Rhododendron ponticum, a species native to the southwestern Iberian Peninsula (parts of Portugal and Spain) and the southern Black Sea Basin (parts of Bulgaria & Turkey)  has been less well received.   It was introduced in the eighteenth century by Conrad Loddiges.  Loddiges grew seed and sold on young plants as an ornamental flowering shrubs for gardens, parks and estates. On country estates and heathland areas, it was planted as cover for game birds as its dense growth offered shelter and protection. It has since spread aggressively and is now considered to be an invasive species. An invasive species is a non-native species that spreads and damages its new environment. R. ponticum poses a threat to key woodland ecosystems, such as Atlantic Oak Woodland.  When this shrub ‘invades’, it comes to dominate the area.  It creates deep shade so the woodland floor becomes a dark and ‘barren’ place. Many ground flora species are lost so that only shade tolerant mosses and liverworts remain.  These plants form a ‘dense mat’ of vegetation that is a barrier to seed germination.  Additionally, there is evidence that as R. ponticum grows, it produces chemicals which inhibit the growth of other species.  This phenomenon is known as allelopathy.  Even when the Rhododendron is removed, it is difficult to reestablish the original flora.  Clearing an area of this plant is difficult and expensive. One effective method involves drilling the stems and injecting herbicide directly into the plant, a targeted approach that uses a lot less herbicide than spraying.  Mabberley’s Plant-book notes that the cost of eradicating the plant from Snowdonia was £30M and that was in 1988. Another Victorian introduction was the grey squirrel. Native to North America, grey squirrels were first released in the UK in the latter part of the 19th century.   One person associated with their spread was the 11th Duke of Bedford  (Herbrand Russell).   He was involved in various animal conservation projects, but he released and 'gifted' many grey squirrels from the estate at Woburn.  The populations of grey squirrels in Regent's Park, London are thought to have come from there. Humans may still be helping the spread of the grey squirrel, albeit unintentionally.  One squirrel was captured on the Isle of Skye (in 2010), it had traveled from Glasgow, as revealed by its genetic profile.  It had probably made the journey as stowaway under a car bonnet. It is important that we are aware of how 'easy' it is for these animals to travel with us.  Their introduction has been disastrous for the native red squirrel populations, due to competition and the spread of the squirrel pox virus.  It is vital that grey squirrels do not colonise areas where the red squirrel still survives. . More recent introductions have arrived due to increased global trade.  Parasites and pests can ‘hitch a ride’ with people, materials or goods as they move across the world.   Climate change is also altering the range and distribution of many plant and animal species.  There is an alert for the Asian or Yellow Legged hornet (Vespa velutina nigrithorax), an invasive, non-native species from Asia.  This hornet preys upon honeybees and other beneficial insects such as hover flies and bumblebees. It hovers outside bee hives, waiting to catch and then kill returning honeybees. The effect on bee colonies can be devastating. The Asian Hornet arrived in France in 2004 (through an import of Chinese pottery) and has spread rapidly. Now it is found in Italy, Spain, Portugal, Switzerland, Belgium and Germany.  Preventing its establishment in the UK is critical.  Any sighting needs to be reported, this can be done through the Asian Hornet Watch. This link downloads a PDF, which gives more information about the Asian Hornet, and contains images comparing the  appearance of the asian hornet, the european hornet, the wasp and honey bee. Other invasive species that are a cause for concern include : Himalayan Balsam Harlequin ladybirds, Signal Crayfish, Eight-toothed bark beetle Citrus long horned beetle Giant Hogweed Thanks to Anton for images.

Acer pseudoplatanus is known as the sycamore in the U.K, or the sycamore maple in the United States. It was first described in botanical terms by the Swedish naturalist Carl von Linné in 1753.  It is thought that the sycamore is an introduced species, as its native range is central Europe and Western Asia.  It probably arrived in this country in the Tudor period (circa 1500 CE).  That it has no old native names is perhaps indicative of its absence before Tudor times, (Some say it has been here longer and have suggested that it persisted in Scotland).  It was recorded in the wild in Kent in 1632.  The sycamore is probably best regarded as a neophyte.  A neophyte is a plant that is not native to a particular area / region and has been introduced in recent history. Whatever its background, the sycamore is now to be found spread across the country. Its spread is due in no small part to the capacity of a single tree to produce many hundreds, indeed thousands of seeds.  The seeds are ‘winged’.  The wing of each seed develops from an extension of the ovary wall.  Two seeds are joined together to form a structure termed a double samara - a 'helicopter-like' device.  The wings catch the wind and the fruit rotates as it falls from the tree. This slows the descent and enables seed dispersal over a greater distance.  The sycamore has been deliberately introduced in a number of countries as it is tolerant of air pollution, salt spray and wind and it readily invades disturbed ground (abandoned farmland, brownfield sites, roadsides etc).  It is now regarded as an invasive species in, for example, New Zealand.  The leaves of the sycamore are simple but large. Each leaf has five distinct lobes and five veins radiate from the base of the leaf into the lobes. The edge of the leaf is somewhat ‘ragged’ with rounded 'teeth'. The lower surface may bear some hairs. The leaves are arranged in opposite pairs around the twigs / stem. In Autumn,  heavy leaf fall can mean that the ground under a sycamore tree can be smothered with a significant layer of the leaves, consequently the diversity of the ground flora underneath the tree may suffer. In spring and summer, the leaves can support large populations of aphids. Evidence of aphids on the leaves may be seen in the form of honeydew; this is the sugary waste of their feeding.   It may fall onto lower leaves (and cars); it provides food for flies and other insects.  The aphids themselves are a food source for ladybirds.  Sometimes the leaves are covered with small, red 'blobs' / projections - these are galls caused by a mite (a small spider-like creature).  The female mite lays eggs in these structures. Sycamores can be coppiced, that is, cut down to a stump which will rapidly produce new growth - for poles etc.  The timber of the sycamore is close grained, white to cream in colour that turns ‘golden’ with age.  It can be used in making musical instruments (violins), furniture, wood flooring There are many other species in the genus Acer, for example, Acer platanoides - the Norway Maple, Acer campestre - the Field Maple, Acer palmatum - Japanese Maple, and Acer saccharum - the Sugar Maple.  All of these have a (diploid) chromosome number of 26. Interestingly, the sycamore has a chromosome number of 52 - the number of chromosomes per cell has doubled.  The sycamore is a polyploid. A couple of interesting historical points about sycamore ;  The Tolpuddle Martyrs' Tree is a very old sycamore. The tree was used as a meeting point (in 1833) for six local agricultural labourers to discuss low wages and their poor living / working conditions.  They are associated with the birth of the trade unionist movement.  The 'Tolpuddle Martyrs' (as they came to be known) were sentenced to seven years of penal labour in Australia and were transported to Botany Bay. Dule trees were used as gallows for public hangings and also used as gibbets for the display of the corpse after such hangings.  One such dule tree lies within the grounds of Leith Hall, near Huntly, Aberdeenshire. This tree is a sycamore. The strong timber of sycamore made it a favoured tree for this purpose. [caption id="attachment_36329" align="aligncenter" width="645"] emerging leaves[/caption]  

The British Dragonfly Society has produced a report “State of Dragonflies, 2021”.  Dragonflies display the usual characteristics of insects, three pairs of jointed legs, three clear divisions to the body, compound eyes and a pair of antennae.  They also have two  pairs of (transparent) wings.  The hindwings are broader than the forewings so they belong to the group - Anisoptera (from the greek unequal wings).  They can fly fast and manoeuvre well.  Their ancestors were some of the first winged insects to evolve. The report notes that Many species have increased their distribution (since 1970), for example, the emperor dragonfly,  the ruddy darter. Though some like the black darter seem to be in decline; this may be associated with a lack of heathland management and the drying of blanket bog areas. Several species have arrived in Britain from Southern Europe for the first time, with others returning after long absences.  The vagrant emperor is a long distance migrant from Africa and the Middle East. It is thought that it might now be breeding more regularly in Southern Europe so that some now migrate northwards more often. Dragonflies are moving northwards across Britain and Ireland (associated with warming temperatures and climate change) Whilst the distribution of species has increased, the actual numbers of different species is not known so it is not possible to say if dragonfly numbers have increased overall. However, compared to many reports on the collapse of insect numbers, it would seem that that many dragonfly species are responding to climate warming and an increase in the number of ponds (for example, see the woodlands blog of the restoration of ghost ponds in Norfolk), lakes, gravel pits in recent years. The larval stages of dragonflies (nymphs) are spent in water. Apart from changing the distribution of various animals (and plants), climate change can have other effects.  Some homeotherms ‘warm blooded’ animals (birds and mammals) are undergoing changes in their body form or ‘shape shifting’.  Sara Ryder et al of Deakin University, Australia has studied several species of Australian parrot and has found that their beak size has increased since the nineteenth century:  this increase in beak size is thought to be associated with better heat exchange.  Other research has reported on changes to tail length in wood mice, also tail and leg size in masked shrews.  The changes are generally less than 10% but they do seem to be responses to changing climatic conditions. Pampas grass (Cortaderia selloana) is a tall, clump forming grass with attractive plumes that can find a home at the coast, in town or in your garden.  It was originally a species native to South America. However, it now has a much wider distribution, mainly due to its use as an ornamental plant though it was also used in South Africa to control erosion on dumps around mines. Each plume can produce tens of thousands of seeds.  Consequently, it is now regarded as an invasive species in many countries. It has expanded across industrial and urban areas, squeezing out native species in coastal regions of France, Spain and Portugal, Now the IUCN (International Union for the Conservation of Nature) has introduced a system to recognise the threats posed by harmful species (such as Pampas Grass)  - The Environmental Impacts Classification of Alien Taxa.

The woodlands blog has previously reported on the danger that the Tree of Heaven presents.  Whilst its foliage and fruits are attractive, it can be a highly invasive plant.  it can overwhelm natural vegetation / species because It grows extremely rapidly It can produces thousands and thousands of seeds in any given year It can spread by underground suckers It produces chemicals that inhibit the germination and growth of other species - a phenomenon known as allelopathy. Read more...

Hawkweeds are wild flowers of dry, grassy places, but also to be found on walls, rocky places, and pavements. Some are regarded as invasive species in some parts of the world. The botanical genus Hieracium is known by the common name : the hawkweeds.  It is thought that the common name derives from the writings of Pliny the elder, who believed that hawks sprinkled sap from the plants into their yellow eyes to dispel dimness.  The genus is a member of the sunflower / daisy family: the Asteraceae. They are closely related to dandelions (Taraxacum) and sow thistles (Sonchus). There are thousands of different Hawkweeds;  but botanists classify British hawkweeds into about 340 “species”, many of which are quite rare. Identifying them is difficult and best attempted when there is fresh growth and new leaves.  The classification of the hawkweeds is difficult, partly because the plants use apomictic reproduction. This means that seeds that are formed without the usual processes of pollination and fertilisation.  Read more...

It seems that the UK is losing the battle to eradicate the giant hogweed.  It is an invasive species which has been described as the country’s most dangerous plant. Many efforts have been made to eradicate this plant.  Local authorities can make use the Wildlife and Countryside Act 1981 and The Anti-social Behaviour, Crime and Policing Act 2014 to enforce control of the weed.  Sadly though Plant Tracker has recorded hundreds of sightings across the four nations of the U.K. Its scientific name is Heracleum mantegazzianum and it belongs to the same family as the wild parsnip, the Apiaceae. It is sometimes referred to as the giant cow parsnip, the giant cow parsley or the cartwheel flower. Read more...

Nearly every report that one comes across says that many plant and animal species are under threat.   The causes are many but may be broadly summarised as  Fragmentation, loss or destruction of natural habitats (as a result of intensive and extending agriculture, roadways, railways etc) Pesticides and pollution (e.g. neonicotinoids, eutrophication as a result of fertiliser use) Impacts of climate change Some of the changes are more obvious in every day terms than others, for example, the drop in insect numbers is revealed by the car windscreen ‘test’ : the splatometer.   A survey of insects hitting car windscreens in rural parts of Denmark [using data collected between 1997 to 2017] found a decline of some  80%. There was a similar decline in the number of swallows and martins, (they depend on insects for their food). Read more...

Atlantic oak woodland is often referred to as the Celtic Rainforest.  It is characterised by lichen covered trees, together with a rich moss and liverwort flora.  The environment is damp and humid, with streams and waterfalls contributing to this. These woodlands have evolved under the influence of the Gulf Stream,  which helps keeps the area warm (and wet). The difficult access and rugged terrain (in some areas) has helped to preserve these woodlands, plus they have not proved suitable for agriculture or ‘industrial forestry’.  Consequently, in many areas,  they have remained in their 'ancient state', going back to the last ice age.  Their sessile oaks are very important for wildlife but as they are not always productive of good timber, they have often been left to grow to maturity.  By the same token, Birch trees have relatively low timber value - which has been their salvation.  Woodlands like this were more extensive in the past covering the Atlantic fringe of Western Europe from North West Scotland down to the South of Portugal.  This type of woodland is rich in terms of biodiversity (primroses, violets, wild garlic, ferns and grasses) and some species are only to be found here and nowhere else in the world. Read more...