The blog tends to write about trees in the context of woodlands and forests, but the trees to be found in hedgerows, parks, streets and gardens are important in many ways.  London is sometimes referred to as an urban forest, as it has some eight million trees within its boundaries.  Though their individual contributions of any given tree may be small, collectively the trees help with : Carbon storage  Carbon sequestration Air pollution removal Removal of pollutants (e.g nitrogen and sulphur oxides) Capture / removal  of particulates Reducing runoff, helping with flood mitigation  Noise réduction temperature regulation. The role of trees in temperature regulation has received some attention recently.   With climate change, many parts of the world have experienced periods of extreme hot weather / heatwaves.  Whilst it is true that extreme cold weather is associated with more deaths than hot, heat waves and the associated deaths are a significant problem.  Heatwaves, such as that experienced in 2015, have been associated with cardiorespiratory problems and premature deaths.   Cities, in particular, record higher temperatures than the surrounding countryside or the suburbs. the so-called urban heat island effect.  The lack of vegetation, the use of air conditioning systems, coupled with the dark asphalt of roads means that heat is retained / trapped; giving rise to the urban heat island effect.  On a summer’s day, some city centres may be some 10oC hotter than the surrounding countryside.  Europe saw its hottest summer last year, and its second warmest year.  Cities in southern and eastern Europe were particularly affected by recent heat waves. They tended to have significant urban heat island effects and low tree coverage.   In contrast, 27% of Gothenburg is covered by trees.  Studies / modelling by the Barcelona Institute for Global Health have indicated that increasing tree cover to 30% of the urban space could decrease the deaths associated with heatwaves / extremes of hot weather (perhaps by a third).  A number of cities, like Barcelona and Seattle have committed to increasing tree cover.  Indeed, Barcelona’s Trees for Life Master Plan is making progress towards its goal of covering 30% of the city with trees,  Barcelona is also encouraging green roofs.  Studies have also shown that ‘green spaces’ can have other benefits from reducing cardiovascular disease, poor mental health, and helping to improve cognitive functioning of children and the elderly.

In recent times, peatlands and areas of blanket bog have been recognised as important parts of our landscape.  Blanket bog is mostly found in wetter and more northern regions - in parts of Ireland and Scotland; in England a lot is to be found in Yorkshire.  Peatlands and bogs play an important part in controlling the run off of water from hillsides, plus they also represent an enormous store of ‘sequestered carbon’. The remains of plants (and animals) have been buried in wetlands but have not decomposed fully (usually due to the acidic conditions). Sometimes large chunks of trees are found in peat bogs, and occasionally even human remains (for example Tollund man) have been found.  Some of the peat deposits are incredibly thick and the material stored in them may be many thousands of years old.  Moorland ‘management’ techniques have been implicated in the severe erosion of certain areas, and the peat (that has accumulated over thousands of years) is being washed away. [caption id="attachment_32147" align="aligncenter" width="650"] Water logged conditions are ideal for peat formation[/caption] The UK has lost many areas of wetland habitat in recent times. A research team lead by Dr Swindles (Leeds University) examined many peatlands and looked at the changes that have occurred over the last two millennia.  They found that the majority of peatlands have become drier.  This drying out changes the role of a peatland from carbon sink to carbon source; i.e. releasing carbon into the atmosphere - contributing to global warming and climate change.  The streams and rivers that permeate these areas often turn a deep, rich brown as this organic material is washed out. [caption id="attachment_34388" align="aligncenter" width="650"] Stream flowing through peat moorland[/caption] Various efforts are being made to help stabilise these valuable ecosystems and a number of techniques to have been tried. At Fleet Moss, a North Yorkshire moor between Wharfedale and Wensleydale, the Yorkshire Peat Partnership project has been working to restore areas of degraded peatland by creating dams and reintroducing wildlife.  The conservationists have been using grass seed to try and stabilise the peat, hoping that as it grows and extends its roots, it will stop the peat from being washed away while allowing bog plants and sphagnum to flourish.  Sphagnum moss can hold 26 times its weight in water.   Their work is already bearing fruit,.  Originally, the land was largely acres of heather, with little variety in terms of the animals and plants that had made a home there. But over time, owls, frogs, foxes and weasels have appeared.  With time, the grass should stabilise the peat and allow bog plants to establish themselves. However, it has not been an easy process. Whilst the scattering of grass seed has worked in some areas, this does not always work everywhere, particularly on exposed sites; seeds can be battered by rain and wind.   Even at the height of summer, the weather on some of England’s highest terrain can be fierce, and scattering grass seeds on areas that are battered by wind and rain has proved to be problematic. So now in some areas a hydroseeder is being used where grass colonisation has failed. This is where green sludge and the bioengineering company TerrAffix come in. TerrAffix uses a hydroseeder to spray the mix of brash (chopped heather), grass seeds, fertiliser and a special adhesive (or tackifier), to areas facing particular challenges.  This equipment has been used to reseed prairies in the States, and can also be used on the steep slopes of motorways,   It will be some time before it is known whether this technique is successful in boggy and peatland areas.  If it does show signs of success then plugs of plants such as bog asphodel and sphagnum will be added, in the hope of recreating a more natural and diverse flora for the areas.   Further information on the restoration of peatlands can be found on Dr. Emma Shuttleworth's web pages and in articles such as this. Featured image is a 'book' made from bog oak.  

In recent times, we have heard much about various initiatives to plant more trees, such as The Queen’s Green Canopy tree planting project to mark the platinum jubilee. Tree planting is part of the government’s plan to mitigate certain aspects of climate change as the trees will absorb carbon dioxide from the atmosphere, which is one of the principal greenhouse gases.  Once absorbed and used in photosynthesis, much of this carbon is then locked away for many years in the form of complex compounds, such as cellulose and lignin. The peak of carbon dioxide uptake by UK woodlands and forests was estimated to be just under 20 million tonnes in 2009.  However, since that time the amount has actually declined.  Many of the conifer plantations that were planted back in the 1970’s and 1980’s have now been felled / harvested, so they no longer contribute to the uptake of carbon dioxide.  It is important that these clear felled areas are replanted and tree cover restored; indeed, in places increased.  Planting rates have risen in Scotland but the performance by the rest of the UK is somewhat limited.  Even with new planting, it takes time for such new forests / woodlands to reach the CO2 absorption levels seen in the 2000’s. Continuous cover forestry (CCF) is a different approach to woodland forest management; it seeks to avoid clear felling and  promotes a mosaic of trees by age and species. There are a number of factors that influence new planting, such as the availability of land.  Using high grade agricultural land for tree planting would affect targets for increased agricultural productivity and domestic food supply.  Also, with climate change and the increasing number of extreme weather events (storms, flooding, drought etc) greater thought needs to be given to risks such as forest fires.  Recent months have demonstrated the ferocity of forest fires in France, California and Portugal.  We cannot assume that the UK will be exempt from such events.  Similarly, we have witnessed powerful storms (such as Storm Arwen) which felled many thousands of trees (and impacted on public services such as electricity and train travel).  The warming climate is also associated with ‘new’ diseases and parasites in our woodlands and forests. New planting needs resilience ‘built in’ to the plan. The Environment, Food and Rural Affairs Committee in its recent report (2021/2) has made a number of important comments in relation to tree planting in the UK, notably : It noted that the Forestry Commission had said that nurseries in the UK will struggle to expand production to deliver the number of young trees required for the Government to achieve its planting ambitions. There is a lack of a sufficiently skilled and large workforce to achieve England’s tree planting ambitions. To meet the Government’s tree planting goals, the UK will need to import seeds and young trees (until domestic capacity increases); and this carries the risk of the introduction of pests and diseases.  

In 1820, John Keats famous poem “To Autumn’ was published.  Its opening line often serves to describe autumn as ‘The season of mists and mellow fruitfulness’.  Indeed, Autumn has arrived here.  Woodlands have been transformed into a 'tableau' of red, yellows, and oranges as the leaves are shed and the woodland floor has become a veritable fungal jungle, (as Jasper has described).  Hawthorn and other bushes are laden with berries, conkers and acorns are generously strewn across woodland floors, squirrels are eating hazelnuts (and hiding them as a winter food store).  But this cornucopia of fruits and seeds may be in response to the long, hot and very dry summer we have experienced.  Trees and shrubs have been stressed by the heat and drought. Some have responded by mobilising their reserves / efforts into producing more fruits and seeds, to ensure that they pass on their genes to the next generation.   Different trees are responding in other ways. Some are ‘holding on’ to their leaves for longer, whilst others (like some birches and rowans) have already shed theirs - in order to limit the damage from wilting and water loss during the intense heat and drought of summer.  [caption id="attachment_39130" align="aligncenter" width="675"] Autumnal colour[/caption] Blackberries appeared early this Summer and few are to be seen this Autumn, some animals (like the dormouse) will search in vain. [caption id="attachment_39026" align="aligncenter" width="675"] Black Bryony berries (photo by Art Symons)[/caption] Will this Autumn be long and mild? It may extend into the traditional winter months. There is also the threat of extreme weather events (like Storm Arwen that brought severe winds across the UK last November).  Whilst we might welcome mild weather (with the high price of gas and electricity), it could be mean an increase in bacterial and fungal infections, not only of plants but also affecting overwintering insects - tucked up in cocoons and pupal cases. Prolonged cold periods, coupled with frosts limit the spread of such infections.  The cold of winter is also the traditional signal for animals like hedgehogs to hibernate.  If they are still active in winter when food is scarce, then they will lose condition and possibly starve to death.  Milder weather in Autumn and Winter also affects the migratory behaviour of birds, some birds may choose to overwinter here.  Some seeds need to experience cold temperatures before they will germinate in the following Spring. Climate change and severe weather events are here to stay until there is a coordinated and concerted effort to reduce greenhouse emissions on a global scale.  On a local scale, our gardens (which represent some 400,000 hectares of land) can make a contribution by encouraging wildlife / pollinators and promoting biodiversity.  Gardens can also help to some extent with extreme rainfall.  During heavy rain, water runs off hard surfaces and into the drains, these may also deal with sewage.  When the drains are overwhelmed by storm water, sewage is discharged into our rivers (and the sea).   Gardens can help by  reducing hard landscaping, so that rain can soak into the soil instead of running off into the drains making use of water butts.  They capture water, so it does not enter the drainage system.  It is also there to use when the garden needs water (and there is a hose pipe ban) mulching the soil with a layer of plant material. It is an effective method of conserving water in the soil and it reduces surface runoff, increasing the infiltration / penetration of water into the soil.  It helps keep the soil moist in times of drought, and helps reduce run off during heavy rainfall.  Particularly important when planting young trees / shrubs. [caption id="attachment_38957" align="aligncenter" width="675"] a light mulch (in Art's garden)[/caption]  

It is depressing to pick up a paper or turn on the news to be met with a catalogue of distressing and difficult stories.  There is also the overarching problem of global warning and climate change.  Only recently, there have been reports of flooding in Sydney after torrential rain, fires are springing up again in Colorado and other States, and India experienced a heat wave (combined with a drought), with some cities experiencing temperatures of 40o+C.  This has resulted in the deaths of individuals, and as the heat wave occurred in the final weeks of the wheat growing season it has killed many crops before harvest.  In Balochistan, the peach and apple harvest has been severely impacted. Here in the UK, there are a number of problems, indeed we have been described as “one of the most nature-depleted countries in the world”.  We have lost plant and animal species, such losses could lead us into an ‘ecological recession’. This occurs when ecosystems systems lack the diversity needed to function well. Much of the damage to (or loss of) our ecosystems is associated with the industrial revolution followed by the  intensification of mechanised farming. The 1950’s and 1960’s witnessed the loss of vast tracts of hedges and the removal of small copses to increase the area for farming / food production, and allow the use of heavy duty mechanised machinery.  There was also the extension of road networks - motorways etc. and urban sprawl /development.  Though woodlands and forests were being eroded long before the industrial revolution; woodland, forest and pasture covered much more of the land than now. There were areas of ‘wilderness’ that were home to animals and plants that have long since gone or are now very rare - ranging from wolves, bears, to beavers and red squirrels. Whilst woodlands were and are havens for many plant and animal species, meadows and pastures have suffered too.  The PlantLife charity has suggested that the UK has lost some 97% of its wildflower meadows during the course of the last century and what remains could be under threat. Lowland meadows are rich sources of biodiversity, both plant and animal, they also store carbon in the soil and ‘knit’ the soil together, so that it is not subject to erosion. [caption id="attachment_38489" align="aligncenter" width="700"] A meadow, partly mown and partly 'wild'.[/caption] Many species are dependent on these habitats, but with the expansion of agriculture and construction of motorways - the landscape has become fragmented and many species cannot across the formidable barriers.  The Scottish primrose is now only to be found on the north coast of Scotland and Orkney, and some orchids are described ‘as just hanging on’.  Species like the common blue butterfly is reliant of bird’s foot trefoil, Greater Bird’s-foot-trefoil, Black Medick and white clover for food for its caterpillars.  The great yellow bumblebee is sadly now one of the rarest British bumblebees. It is limited to flower-rich areas in the Orkneys, Caithness and Sutherland. It is particularly associated with red clover. It is a large species, and was once widespread across the U.K. Creating space and opportunities for wild flowers has been PlantLife's foremost objective from “No mow May”, “Save nature on our roadside” (see the woodland blog here and here) ’Fight for sites” all of which aim to increase the number of sites for wild flowers and their pollinators to flourish.  The Scottish Government has been helping establish wildflower meadows at some of its national nature reserves - notably St Cyrus, Flanders Moss and Forvie, and they are working with PlantLife to create an action plan for Scotland’s grassland.  It is keen for farmers to be involved, offering areas of wild flowers on their farms.  By increasing the areas in which wild flowers (and their associated insects) can flourish, the connectivity can be restored (at least in part).  The creation of biological corridors allows plants and animals to move, which is particularly important in these times of climate change.  

If bumblebees are exposed to heat stress during their development (they go through four stages : egg / larva / pupa / adult or imago) their bodies develop asymmetries.  The wings in particular are affected, so the left and right wing are shaped differently.  This asymmetry can be measured and has been used by a team from the Natural History Museum and Imperial College to investigate how changing climate over time has affected bees. They investigated four species of bumblebee [Bombus hortorum, B. lapidarius, B. pascuorum and B. muscorum] in museum collections that dated back to 1900 CE.  The bees were ‘held’ in collections at various museums  [Natural History Museum (London), National Museums Scotland (Edinburgh), Oxford University Museum of Natural History, Tullie House Museum and Art Gallery Trust (Carlisle) and World Museum (Liverpool)].   [caption id="attachment_38920" align="alignleft" width="300"] Landing[/caption] Using digital images of many bees collected at different times over the last 130 years, they measured the asymmetry of their wings.  The data from these measurements were then correlated with information about annual rainfall and mean annual temperature in the year the bee was collected.  It became clear that wing asymmetry was associated with hotter and wetter years; and that each of the bee species displayed greater asymmetry, hence stress, in the second half of the twentieth century.  As hotter and wetter conditions are predicted to become more frequent with climate change, it is probable that bumblebees will experience greater stress, indeed they may be in for a ‘rough time’ as this century progresses. Apart from investigating wing asymmetry, the team used a leg from some of the historical specimens to analyse the DNA / genetic make-up of the bumblebees (B. lapidarius).   With the DNA data from these bees (dating aback over a century),  the Natural History Museum and the Earlham Institute were able to construct a ‘reference genome’ - a standard against which they can see how bee genomes change over time.  This may ultimately reveal how bees are adapting (or not) to a changing climate / environment.

In recent years, there have been a number of initiatives to plant millions of trees, both here in the UK and in many other countries.  For example, http://www.stumpupfortrees.org/bryn-arw-common-pilot-plant/ https://www.nationaltrust.org.uk/press-release/national-trusts-plans-for-20-million-right-trees-in-right-places-take-root https://queensgreencanopy.org https://onelifeonetree.com https://earthwatch.org.uk/get-involved/tiny-forest?gclid=EAIaIQobChMIiqyVxOvA9w https://earthwatch.org.uk/get-involved/tiny-forest The trees are not being planted to increase timber production. They are to help offset global warming as trees take up carbon dioxide through photosynthesis, so they remove this greenhouse gas from the atmosphere thus helping to offset global warming. However, planting just ‘any old tree’ is not going to solve anything, so scientists from Kew Gardens (RBG Kew) and Botanic Gardens Conservation International (BGCI) have set out ten ‘golden rules’ for reforestation. The "Kew" guidelines have been summarised as below : Protect existing forests first Put local people at the heart of tree-planting projects Maximise biodiversity recovery to meet multiple goals Select the right area for reforestation Use natural forest regrowth wherever possible Select the right tree species that can maximise biodiversity Make sure the trees are resilient to adapt to a changing climate Plan ahead Learn by doing Make it pay However, fast as trees are being planted in many places, there have been substantial losses of forests and woodlands in recent times.  The blog has reported on the extensive fires in Sweden, and the Mediterranean.  The recent fires in boreal regions have been extensive and worrying - they have affected Canada, Russia and Alaska.  In the last year, Russia lost some 6.5 million hectares of tree cover.  Boreal forests are often portrayed as vast tracts of ancient, untouched wilderness. Whilst it is true that the boreal region is in itself ancient, the boreal forests are generally composed of relatively young trees trees (as compared to the oaks etc. found in temperate forests and woodlands). Historically speaking, boreal forests have renewed themselves through natural regeneration, after fires.  But now with climate change and rising temperatures, conditions are drier and the fires are more frequent and more intense.  There is also a problem of  damage by insects. The loss of forests in tropical and sub-tropical regions has been a cause for concern for many years, not only because of their importance in generating oxygen and removing carbon dioxide but also as they represent areas of great biodiversity.  Sadly, the loss of such forested areas continues, despite the commitments made at COP26  (where some 141 countries committed to "halt and reverse forest loss by 2030.").   [caption id="attachment_38123" align="aligncenter" width="700"] clear felling in progress[/caption] Forest / tree clearance occurs as a result of clearance for activities such as cattle ranching or the production of palm oil.  However, as a result of the events in Ukraine / Russia the availability / prices of certain oils is now high.  This is also true for palm oil so the ‘temptation’ to convert forested areas into palm oil plantations is significant.   Whilst there is clear evidence that various countries and governments are involved in the creation of woodlands & forests through tree planting initiatives, and working to reduce the loss of primary forests to agriculture or timber extraction, there is concern that nature itself is beginning to work against us. Changing weather patterns, increasing temperatures and extreme climate events are already affecting many forested ecosystems.  

Looking around the garden this morning one might be forgiven for thinking that autumn is already here.  Several trees seem to think the short days of autumn have arrived and are preparing to shed their leaves. Certainly the walnut and hazel are of this opinion.  However, other signs indicate that this is not the case, my twenty year old cedar has died, as have several Cryptomerias and other conifers - this despite assiduous trips with the water can.  In fact, the plants are responding to this summer’s weather, a long period without rain (or very little) plus the very hot weather that we have experienced; particularly in the South and South East.  The plants are not reacting to any changes in day length but to drought. Plants detect changes in the photoperiod they experience through their phytochrome system; under normal circumstances their biological clock will tell them when to prepare for winter.   Whilst many well established trees and plants with extensive root systems can withstand a period of drought, younger plants or those in poor or freely draining soil are likely to die.  Such plants simply cannot take up enough water to replace that lost through transpiration; that is, water evaporation through the stomates (pores) in the leaves.    The intensity of the heat this year coupled with the reduced rainfall has affected many plants and trees and it may be some time before we see the full effect of this summer’s weather.  Beech trees suffer more during periods of droughts because they have shallower roots, while oaks reach moisture deeper in the soil and continue to grow.  In the drought of 1976, many beech trees died and survivors often exhibited reduced growth some 40 years on*. Some plants respond to drought stress by bringing forward their reproductive process, so that fruits and seeds are produced early.  This is an attempt to ensure the survival of the species for when conditions are more favourable to growth.  The Woodland Trust, noted for its phenology records, recorded ripe blackberries in late July (lots of reports on its page on Facebook).  Hawthorn, Rowan, Holly and Elder have all been recorded as fruiting earlier this year.  This was true of the filbert in my garden this summer.  This earlier production of fruits and seeds may have ‘knock on’ effects on the wildlife that feed upon them.   Whilst the effects of the extreme weather are obvious in our parks, gardens etc, the effects on rivers and streams are dramatic.   Chalk streams, in particular, have been affected; they are unique habitats.  The River Ver is a chalk stream in Hertfordshire.  The summer has seen large sections of its upper reaches reduced by several kilometres due to the hot weather (and water abstraction).  The effects in and around such streams may be felt for many years as the water levels fall so the habitats for fish, amphibians and invertebrates (such as dragonflies / mayflies) are reduced or lost.  Recolonisation of such drought impacted systems can be slow and prolonged.   An accessible and detailed paper on Beech trees and drought is available here : research gate.net [caption id="attachment_22186" align="alignright" width="300"] Mature Beech on Box Hill, Surrey.[/caption] [caption id="attachment_10575" align="alignleft" width="300"] Mature beech[/caption]