Trees are remarkably resilient.  In various forms they have been arounds for millions of years.  They have survived asteroid impact (66 million years ago), and a series of successive ice ages.  However, in more recent times they have faced a new challenge, the relentless march of humankind. Early societies felled trees for timber for dwellings, boats*, wood for fire, making tools, as part of ‘flash and burn’ agriculture to create a ‘swidden’ to grow food.  The material felled to create a swidden was allowed to dry and then burnt, the ash released mineral nutrients into the soil for the crops.  As more complex civilisations / societies evolved, there were attempts to restore degraded forests / bare land, and  to protect forests.  The Zhou (Chou) dynasty established a ‘forestry service’ over two thousand years ago, and in India the emperor Ashoka (268 -232 BCE) ordered wide scale reforestation.  Much later in the Middles Ages there were efforts to restore degraded areas, for example, around Nuremberg in the C12th.  Most of these early efforts were concerned with increasing timber production or the mitigation of natural disasters.  In the last two centuries, significant areas of natural forest and woodland have been lost, increasing the risk of soil erosion, flooding and disease (as animals are displaced). In the last century, the percentage cover by forest / woodland in some countries (for example, the UK) was low so vast areas were planted with a single species. Fast growing species (conifers such as pines, spruce and larch) were often grown on what was regarded as marginal land, creating plantations.   In some parts of the Mediterranean, Eucalyptus was planted.  These were species that could cope with the challenging nature of the soil and / or the  topography.   Many of the European initiatives met with some success in terms of timber production and / or the stabilisation of degraded areas (for example, reducing erosion).  Such schemes also created jobs, contributing to the local economy.  But when grassland or heathland were used to create single species plantations, this was often accompanied by a loss in biodiversity. In places, the introduction of non-native species has been challenging as they have become invasive, for example, black cherry. The success of any scheme is dependent on Sound planting techniques and aftercare Selection of the right species for the area The co-operation / involvement of local peoples. Mass planting of a single species can also contribute to the rapid spread of disease / pests (e.g.bark beetles, pine procesionary moth).  Vast swathes of coniferous forest were affected by acid rain (associated with sulphur dioxide from the burning of fossil fuels) in the last century.  This was termed Waldsterben [Wald=forest + sterben=to die].   Problems such as these, coupled with increasing environmental awareness contributed to a rethink of the aims and objectives of forest management / renewal / restoration. However, there were examples where ecological recovery was good, for example, some spruce and black pine ‘monocultures’ were diversified through the planting of a understorey of broadleaved trees, as in Slovenia. In recent times, timber production, control of erosion and reduction of disaster risk remain relevant still, but the importance of biodiversity, resilience and ecosystem services are now uppermost.  There is a move from ‘quantity to quality’ of forest and woodland.  In many countries, a growing interest in recreation and tourism (recognising the importance of green space for mental and physical well being), coupled with growing environmental concerns and recognition of climate change has emerged.   Forest and woodlands across the world, from the boreal regions to the Equator are under threat.  Many have been lost or badly degraded, and are in desperate need of restoration.  Forests are no longer regarded as sources of timber, but are important providers of ecosystem services, such as the mitigation of flooding. So, in more recent times they have been efforts to restore and repair forests and woodlands.  Homogenous and dense plantations / forests in boreal regions had clearings created to allow light demanding species to establish.  Limitations have been placed on clear cutting, and the use of fencing, tree protectors have [caption id="attachment_41889" align="alignleft" width="300"] squirrel[/caption] helped to reduce browsing pressure (by deer / squirrels etc).  One means of promoting biodiversity is ensuring that the woodland / forests offer deadwood.  This provides a ‘home’ to species as varied as woodpeckers to saproxylic beetles. These beetles help break down wood so that it can be further broken down by fungi and bacteria, returning nutrients to the soil. Tree girdling was a technique used in Finland to create deadwood, it severs the conducting tissue (phloem) so that the supply of sugars is interrupted.  Thought is now given to the selection and introduction of tree species that are adapted and resilient to anticipated climate change impacts.   Though countries have adopted a variety of techniques in recent times, the extent of forest and woodland restoration has been largely limited by the funding available.  Restoration does not come cheap, funding over significant period of time is needed, and time itself for the effects of  the measures to become apparent. For detailed information on forest restoration see - https://link.springer.com/article/10.1007/s40725-024-00235-3 Intereesting facts : Henry V111’s flag ship, the Mary Rose , was built using oak and elm. It was the first big ship of the Tudor naval fleet and it is estimated that over 600 trees were needed for its construction,. That is equivalent to about 16 hectares of forest / woodland.  And Cver 370 species are supported in the territories of the Karen swidden farmers in northern Thailand.  

Bees and solar parks As the country tries to move towards carbon zero, so we see more and more solar parks  / farms ‘springing up’.  Whilst they do create clean energy, they also take up a lot of land, and it is important to see if such solar parks can offer other commercial or environmental benefits.  One suggestion is to place honeybee hives on such parks.  The bees could provide a pollinating service to surrounding crops / farmland.  Researchers at Reading and Lancaster Universities have studied detailed land cover maps / crop distribution patterns to estimate the economic value of deploying honeybees in solar parks.  Their investigations suggest that a variety of crops from oil seed rape, soft fruits to apples and pears could benefit from such an arrangement.  The benefits would vary across the UK, with the benefits being greatest in the East and South of the country.  Care would need to be exercised though to ensure the placing of hives did not disturb the foraging of wild pollinators, such as carder bees, hoverflies etc. Are plants sulphur deficient? Much has been written about the importance of plants nutrients, especially NPK; that is to say nitrogen, phosphorus and potassium.   However, little is said about sulphur.  However, researchers in Groningen, Graz and Cologne have been looking at the effects of sulphur deficiency, particularly in relation to the colour and shape of the flowers formed.  The work focused on Brassica rapa, a member of the mustard family.  When it was subject to ‘mild’ sulphur stress (by limiting the sulphate in the growth medium), the flowers that formed were smaller and paler - not the usual bright yellow.  They were also likely to be mis-shapen. Colour and shape are features by which pollinators recognise flowers and then visit them. Pollen production by the flowers was also affected; smaller pollen grains were formed.  This may in turn affect the pollinators who visit the flowers foraging for food. In the relatively recent past, sulphur deficiency may not have been a problem due to acid rain, which would percolate through the soil, forming sulphates.  [In the twentieth century, acid rain formed as a result of the release of sulphur dioxide (and nitrogen oxides) into the air through the burning of fossil fuels.  However, various clean air acts have ensured that there is now much less SO2 in the air.] Annual rings, water availability and earthquakes. Christian Mohr (scientist from the University of Potsdam) was studying the transport of sediments in rivers in Chile in 2010 when a massive earthquake shook coastal areas of the country.  When he was able to return to his studies, he noticed that streams in the valleys were flowing faster.  He reasoned that this was because the earthquake has literally shaken up the soil, so that it was now more permeable and ground water could more easily flow down from the ridges.  As a result of increased water supply, he thought that trees down in the valleys would grow more than those on the ridges. He and colleagues drilled out plugs of wood from valley trees and ridge trees, and back in Potsdam they examined the tree rings under a microscope.  They also looked at the uptake of different isotopes of carbon as a measure of photosynthesis.  They found that trees from the valley floor experienced a small but noticeable growth after the earthquake, and this lasted for weeks or months, whereas the trees of the ridges grew more slowly.   It is possible that analyses like these, when combined with other information, could help identify significant historic disturbances. Rising temperatures. Recent years have seen periods of very hot temperatures, Such extreme weather events have been seen not only in the UK but across the globe (Arizona , Victoria Australia, Indonesia).     Extreme heat (and drought) have been known throughout history, but it would seem that extreme events are now more common.  The first two decades of this century are among the warmest on record; this warming is associated with increasing levels of greenhouse gases (due to human activity). Prolonged heat is not without its effects on us, it leads to sweating, teaches, fatigue, dehydration and heat exhaustion.  The very young and the elderly are most at risk from ‘heat waves’.  A 2003 heatwave across Europe is said to have caused several thousand  'excess' deaths’, mainly of the elderly.  Even gradual but sustained warming of the climate can have its effects.  For example, Silwood Park (Imperial’s research station) has commented that though it is now November, they have not recorded a single frosty night - normally they would expect to have three in a ‘normal’ October.  Snowdrops are appearing earlier, and some migratory species are changing their pattern / timing of migration. Across the world, different species are being affected in different ways.   Thick billed murres (type of guillemot, found in and around the Hudson Bay) have a high metabolism to deal with the cold waters into which they dive - they are cold adapted animals. On warm days (when the temperature is 21cC or above) they are dying whilst sitting on their nests - incubating their eggs.  They struggle to keep cool, if they spend more time in the water then they leave their eggs exposed to predators (like gulls and arctic foxes).  Similarly boreal and arctic bumblebee species are sensitive to heat stress, succumbing to stupor; other work indicates that some European / mediterranean species are now to be found in areas of the arctic circle - as a result of changing climatic ‘norms’.  Wild dogs are adapted to deal with heat, but if the temperature goes beyond a certain point they stop hunting, consequently their pups / offspring are less likely to survive. Warming temperatures not only affect animals but they also contribute to the increasing number of harmful algal blooms (in lakes and off shore regions).  These blooms can be dangerous to many animals (including humans) and when they die back they ‘suck’ oxygen out of the water - creating ‘dead zones’.  One species of alga (Karlodinium veneficum) which is known to produce toxins has been shown to acclimatise to higher temperatures (up to 30cC). As climate change and research continues, we will no doubt see further examples of how animals and plants are being affected by changing temperatures / climate .

In recent times, new or different threats have emerged to upset the balance of woodland and forest ecosystems.   In the 1960’s and early 70’s concern focussed on the effects of air pollution, particularly the effects of acid rain.  This type of pollution was characterised by the deposition / assimilation of sulphur dioxide and its derivatives (sulphuric & sulphurous acid), plus various nitrogen oxides.  This air pollution was largely due to industry and traffic. Some of the most striking effects of ‘acid rain’ pollution were seen in the coniferous forests of Germany - where it was termed : Waldsterben [Wald=forest plus sterben=to die].  Read more...

The woodlands blog has previously reported on the havoc being wreaked by bark beetles.  Such beetles may be small (about half a centimetre in length) but their effects on the western forests of North America is colossal - indeed some parts have lost 90% of their conifers.   Outbreaks of these beetles have been increasing in size and severity. The beetles onward march was generally kept in check by long and cold winters, but with warmer temperatures (especially in the winter months) and a longer season for reproduction bark beetle populations have been gaining ground, even making their way into parts of the boreal forest of North America. Read more...

Nitrogen pollution, in the form of nitrates, ammonia and various oxides of nitrogen, is a threat to ecosystems, ecosystem services and biodiversity.   Monitoring and measuring such pollutants in rain and air borne particles is expensive and, ideally, needs frequent samples. It has been estimated that some 400,000 tonnes of airborne pollution are deposited over Britain each year.  Research by Dr H Harmens et al at the Centre for Ecology and Hydrology (Bangor) has indicated that there may be a simpler and cheaper way of gauging nitrogen pollution  - through the assessment of the state of local moss populations. Read more...

The wholesale destruction of ancient woodland through farming and forestry has diminished but new roads,  bypasses and the installation of infra-structure & services (such as utilities & power lines) can still be a problem.  In recent times, new or different threats to ancient woodlands have emerged to upset the balance of woodland ecosystems. In the 1960’s and early 70’s concern focussed on the effects of air and acid rain pollution .  Such pollution was characterised by the deposition of sulphur dioxide and its derivatives (sulphuric & sulphurous acid), plus various nitrogen oxides. Read more...