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. 

Wetlands. In the past, many areas of wetlands have been drained and ‘dried out’.  Now it is recognised that this is counter-productive in terms of carbon storage / sequestration and biodiversity, so there are now measures to restore wetlands. The hope has been that restoration of wetlands will do much to restore the variety of plants and animals (and help carbon storage).  However, research by the University of Copenhagen suggests that such projects might be ‘struggling’. The study examined ten wetlands (near the River Odense) that were restored between 2001 and 2011.  The restoration involved the removal of drains and ditches, and allowed streams to meander again instead of flowing in ‘straight channels’.  The aim of the project was primarily to reduce the leaching of nitrogen and phosphorus from adjacent farmlands, and hope to see greater diversity of plants (e.g. marsh orchids, globeflower, tussock-sedge and ragged-robin).   The ‘restored’ wetlands were botanically poor (whether restored in 2001 or 2011), they had only a quarter of the plant species compared to natural wetlands.  This may be due to  the continued input of nutrients (from agriculture), which encourages species that are ‘nutrient hungry’ at the expense of others. the ‘difficulty’ of wetland species to disperse from one area to another. It may be that future restoration programs will need to include planting / seeding of additional wetland species. It has been suggested  that it could take the best part of a hundred years for the restored wetlands to resemble natural wetlands. Redwoods and relatives. Previous posts have talked about the special features of the giant redwoods (their height, age etc).  Over the last 150 years, they have ben subject to the pressures of commercial logging, clear felling and more recently high intensity fires.  Indeed, the fires have been of such an intensity that seed banks in the soil have been destroyed. Now they have been subject to genomic analysis, that is their DNA has been analysed and sequenced.  The first conifer genome to be sequenced was that of Norway Spruce, then that of loblolly pine.  These suggested that conifer genomes are large (3 to 10 times larger than the human genome), with repetitive sequences.  Coast Redwoods are hexaploid, that is, they ave six copies of each chromosome (we are diploid, that is, have only two copies of each chromosome).   The DNA of a coast redwood has  27 billion base pairs of DNA, the giant sequoia has 8 billion; by contrast we have circa 3 billion.   It is hoped that the Redwood Genome project will see the restoration of areas of coast redwood and giant sequoia that have been lost over the years. The genomic analysis will help inform and guide management strategies, ensuring genetic diversity in the newly planted tree seedlings. Such a strategy will (hopefully) enable newly planted areas to survive and thrive — in the Anthropocene. More on chromosomes Just as it has recently been shown that Coast redwoods are polyploids (i.e. have extra sets of chromosomes), so recent research in the Czech Republic has shown that the common nettle [Urtica dioica] has different ecological ‘preferences’ depending on its chromosomal status.  Nettles can be diploid (2n = 26) or tetraploid (2n = 52).  The tetraploid nettles seemingly have a broader ecological tolerance and a wide geographical distribution, whilst the diploid nettles occur in a narrower range of ecological conditions. Details of this research can be accessed here (note link opens a PDF) and Plants for a future has lots of information on nettles.    

At the end of the last Ice Age, the British Isles were recolonised; plant and animal species from the continent moved across the 'land bridge’ (doggerland) that connected us to Europe.  Trees, shrubs and plants began to move into the areas ‘released’ from the ice sheets, forests formed in many places.  At first, the forests were largely coniferous and they extended across the north of the UK to swathes of Europe and Asia: they formed an enormous area of boreal coniferous forest.  This vast array of trees provided shelter and food for a variety of animals -  wolves, lynx, elk and many other species.  Since the Ice Age,  forests and woodlands have been cut down for farming; trees felled for timber, sheep and deer ate young shoots and stopped native trees (like the Scots pine) from re-growing. Read more...

Radiant energy from the sun falls on the Earth; some of this energy is absorbed by the planet and its atmosphere.  Some of the energy is radiated back into space.  The balance between the absorbed and radiated energy determines global temperature.  This balance is changed by a number of factors - the intensity of the solar energy, cloud reflectivity, the absorption of energy by various gases or surfaces. The reflectivity of the Earth’s surface  (the albedo) influences the amount of light energy that is reflected back into space. Snow has a high albedo, that is, it reflects much of the light back out into space.  Dark objects (like conifer plantations) reflect less light / radiation and absorb more thereby trapping heat that would otherwise be reflected back into space. The amount of energy that is ‘retained’ is also influenced by the presence of particular gases in the atmosphere - the so-called 'greenhouse gases', notably carbon dioxide and methane.  The amount of carbon dioxide in the atmosphere has increased dramatically from 280 ppm during the 10,000 years up to the mid-18th century to 415 ppm (as of 2019).  This increase has certainly contributed to the changes in climate that we have witnessed in recent years - extreme weather events such as heat waves and flooding.   Read more...

Having been flooded out of my house ten years ago, due to a flash flood, I know that the pain and sadness of flooding is immense.   My heart goes out to those who are battling the rising water levels caused by some of the most extreme weather for a century.   It’s not surprising that in their anger, people are lashing out at the nearest targets. Not enough dredging ?   Dredging isn’t the answer.   Increasing the capacity of the river channel by a small amount is not going to contain the huge extra volume of water spreading across the floodplain.   And it will probably just dump the water on someone else downstream. Read more...

"That's the wettest woodland in the county" is a comment people often make about their local woodland.  But this comment cannot be literally true for very many woods.  It seems that people are often surprised by how wet woodlands can be and hence are often keen to drain them.  However, wetlands are important habitats and can be home to unusual birds, invertebrates and mammals. Visiting the London Wetlands Centre recently I discovered how a former sewage works has been transformed into a wildlife sanctuary over the last 20 years.  Having become redundant as a sewage treatment plant, because of the creation of the Thames Water ring main, negotiations in the late 1980s led to part of it being developed for housing by Berkeley Homes (about 40 acres) and the remainder Read more...

No-one likes getting their feet damp, but wet woodland has its place and is certainly valuable from the perspective of diversifying habitat. Read more...