The last century saw the destruction of many hedgerows, particularly in farming areas like East Anglia.  The logic behind this was : to increase field size and  allow ease of access of machinery, like combine harvesters that were coming available at that time.   Whilst the loss of the hedgerows and the associated wildlife is well documented, the loss of ponds during this time has not attracted the same level of attention.  Many hundreds of ponds were filled in, to give a few more metres of arable land.  The whereabouts of some of these ponds can sometimes be found on old ordnance survey maps.  Many were located on farmland and their origins may extend back centuries to when they were created as marl or clay pits, sometimes for the watering of livestock.  Some were formed in depressions (pingos) left after the last ice age. There are still  thousands of ponds across the UK but many are polluted to a greater or lesser extent, or drained.  The pollution may be associated with the the surrounding land use or agricultural runoff. Runoff may take the form of nitrates / phosphates from the use of fertilisers.  In freshwater systems, these nutrients can cause eutrophication. Other agricultural chemicals may enter ponds and water courses - insecticides, fungicides, herbicides etc. Consequently, out of the thousands of ponds, only a very small number provide a suitable habitat for pond organisms such as the medicinal leech.  Leeches are rarely found for the reasons cited above but also because, as agriculture became more mechanised and less reliant on ‘animal power’ [horses, oxen], the ponds  (or wetlands) are no longer visited by these animals, which leeches would have fed on.  Leeches used to be abundant, but their number declined when their use in blood letting was largely abandoned, and their natural habitats were drained or damaged.  The medicinal leech is one of the largest leeches found in the UK, it can grow to a length of ten centimetres, and may have stripes / patterns on its body.  Some of the ponds that are home to medicinal leeches have been designated  Sites of Special Scientific Interest.  Since historic times, the extraction of blood by leeches was deemed to be a ‘healing process’ for patients. This practice of hirundotherapy / bloodletting spread widely and the collection of leeches resulted in the over-exploitation of many populations.  The leeches were used widely in the treatment of many conditions and  diseases such as cholera, regardless of whether or not they were effective.  At one stage, leeches were in such demand that there were ‘leech farms’, and  people could earn a living as leech collectors.  Indeed, so commonplace was leech collection that Wordsworth wrote about it in his poem Resolution and Independence : “He told, that to these waters he had come To gather leeches, being old and poor: Employment hazardous and wearisome! And he had many hardships to endure: From pond to pond he roamed, from moor to moor; Housing, with God’s good help, by choice or chance; And in this way he gained an honest maintenance.” Although the use of medicinal leeches was discredited and virtually abandoned for many decades, they are medically effective in certain circumstances.  The leeches produce a saliva which  contains a number of different proteins. These help the leech to feed by keeping the blood from clotting, and actually increasing blood flow to the leech at the point of attachment.  Some of these proteins act as anticoagulants (notably hirudin),   It is also possible that the saliva contains an 'anaesthetic / antiseptic' as leech bites are generally not painful. These leeches have now found a use in microsurgery.  They are used to stimulate the circulation in tissues which experience post-operative congestion.  They are helpful in finger reattachment and reconstructive surgery of the ear, nose, lip, and eyelid. The creation of a network of new or restored freshwater ponds across the landscape will be needed if natural populations of the leech are to expand. 

Images of deer in a woodland clearing may seem charming, but quite how deer and woodlands interact is not fully understood. It is certainly the case that deer affect tree regeneration;  they browse on saplings and can cause extensive damage to bark (through territorial behaviour / antler rubbing) to larger trees.  The lower levels of the plant communities are also affected by deer.  By changing these, deer also can change the animals to be found in this lower layer of a woodland. Research by Dr. Simon Chollet and colleagues showed that deer interaction can influence soil water availability,  and soil fertility. Their study looked at the role of Sitka black-tailed deer on the plant communities in forests in parts of western Canada. Chollet et al. examined twenty areas where deer were excluded for some two decades. An exclosure is a limited area from which browsing animals, such as deer, are excluded by fencing or other means. Unsurprisingly, they found that deer did have a significant effect on the plant communities. The exclusion of deer resulted in an increase in vascular plant richness and cover, though bryophyte (mosses etc) cover declined. They also found that with the deer gone,  the exclosures started to develop broadly similar plant communities.  There was no increase in beta diversity - that is the development small, localised communities of varying character. It was suggested that the dominance of certain species within the exclosures was linked to historic over-browsing.   Consequently, those plants that are able to withstand the presence of deer over time are best placed to achieve ‘dominance’ once this grazing pressure is removed.  This might explain why the different enclosures developed similar vegetation and plant species.    Biotic homogenisation has been seen in the UK woodlands, as was discussed in a previous blog.  It can be the result of introduced species, pollution (eutrophication - increased nitrate and phosphate levels), which allows botanical thugs (like nettles) to dominate, or poor woodland management.

Stinging nettles (Urtica dioica) are widespread across the UK.   They are found nearly everywhere; in woodlands, hedgerows, gardens and on disturbed ground. Nettles have been found in and around human settlements since the earliest of times; they probably formed part of the diet in Stone Age times.  Nettles also provided fibre for clothing.  A piece of nettle cloth has been found in Denmark's richest known Bronze Age burial mound (Lusehøj). It is associated with the burial of a rich and powerful man - after the burning of his body, his bones were wrapped in a cloth made from stinging nettles and then placed in a bronze container. Stinging nettle pollen is often to be found in soil sample cores, suggesting it is one of our native plants though human activity and movement may helped it to extend its range.  Nettles can tolerate a wide variety of soil conditions, though they seem to like moisture, and soils rich in nitrate and phosphate. In favourable conditions, they can grow to a metre or more in height. There are patches of stinging nettles that mark phosphate-rich debris from abandoned villages and sites of human occupation from more than 1500 years ago. Nettles have the potential to grow and expand in woodlands, perhaps aided and abetted by the increasing levels of eutrophication (nitrate / phosphate enrichment from air borne pollution).  Indeed, they can become 'botanical thugs' overwhelming other members of the ground flora  / herb layer. 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...

Most regard woodlands as a beautiful and important part of our countryside, and feel that they can exert a profound and positive influence on our emotional state.    Time spent wandering through the woods can have a relaxing and calming effect. Woodland only forms a small percentage of our countryside (about 13%), and some of that is dominated by conifers planted in the post-war period for timber production; however, the area covered by broad leaved trees is now increasing.    Despite this, our woodlands do harbour a wonderful variety of wildlife (think of the red squirrel, the nightingale, the dormouse) but there is concern that woodland plants and animals face a number of threats - many species are in decline.   Why is this ? Read more...

Many parts of the UK have recently experienced the driest October to March period for a long time.  This was followed by two relatively dry Spring months - April & May.  The Met Office Map of the UK found here - shows the rainfall pattern across the country as a percentage of the average rainfall for a 30 years period. This has not only affected gardeners and farmers but river systems across the United Kingdom.  This is bad news as many rivers have already had too much water taken from them (abstracted) - for farming & industry.  The problem of over-extraction of river water is not helped by the fact that one fifth of all piped water is lost through leaks.  Thames water was recently fined millions for failing to reach its leak reduction targets. Read more...

Biotic homogenization has been defined as follows "the process by which species invasions and extinctions increase the genetic, taxonomic or functional similarity of two or more locations over a specified time interval. Biotic homogenization is now considered a distinct facet of the broader biodiversity crisis having significant ecological, evolutionary and social consequences."   Basically, it refers to an increasing similarity in the make-up of the plant communities found in different places - a bit like High Streets, each of which used to have a special character or 'signature', now it is difficult to distinguish one from another. In many cases,  biotic homogenization involves the replacement of local floras and faunas with 'introduced species', sometimes referred to as aliens.   Examples of plants that have been introduced and spread are himalayan balsam and japanese knotweed.   Read more...

Nitrogen is an important plant nutrient.  Generally, it is taken up in the form of nitrate (NO3) and it is used in the formation of amino acids, proteins and the constituents of the genetic material (DNA).  Some plants fix atmospheric nitrogen through the use of symbiotic bacteria in root nodules. However, modern / intensive farming involves the addition of nitrogen compounds in the form of manure, sewage sludge and chemical fertilisers. Couple this with the aerial deposition of nitrogen compounds, estimated at 400,000 tonnes / yr from car exhausts etc. (in the form of ammonia, nitrogen oxides) to give the total burden of nitrogen pollution. Pollution from such widespread sources is referred to as diffuse contamination. Read more...