Blog - Woodland Web Updates
Woodlands web updates 11
Hungry caterpillars. Many insects feed upon the leaves of the canopy in woodlands and forests. They can vary from aphids, leaf miners, sawflies to butterfly and moth caterpillars. Every few years there are significant ‘outbreaks’ of particular moth caterpillars, for example, gypsy moth caterpillars. These caterpillars feed on the leaves of many broadleaved trees but are 'partial' to oaks [and poplars (Populus species)] in woodland / forest situations. When their numbers of high, they can cause significant defoliation. A study undertaken by researchers at Cambridge has revealed that moth outbreaks can have significant effects on the surrounding ecosystem(s). As the numbers of caterpillars are so high, they eat large amounts of leaf material. This has a number of consequences The amount biomass in leaf fall in the autumn is reduced The caterpillars convert the carbon-rich leaves into nitrogen-rich frass. The caterpillars are not very good at using the leaf nitrogen for their own ends. Frass is the excrement / faecal material produced by the caterpillars. This frass can pass into streams / waterways and end up in lakes and ponds. Once in the lakes etc, it changes the chemistry of the water and it favours the reproduction of bacteria that release carbon dioxide. This happens at the expense of the algae, which remove carbon dioxide from the atmosphere. The amount of carbon entering streams and lakes is reduced in caterpillar outbreak years. Caterpillar outbreaks significantly affect the carbon and nitrogen cycles in woodlands and associated freshwater systems. Details of the work (which focused on forest and lake systems in Canada) can be accessed here. Air pollution and wood burning stoves. Tiny particles called PM2.5 (released from a variety of sources, such as road traffic) pollute the air. They are harmful to our health as they can pass into the lungs and out into the blood stream. They then circulate around the body and end up in various organs. One source of these tiny particles is the burning of wood in wood burning stoves. One recent study has suggested that wood burning may account for some 40000 early deaths in Europe each year! The biggest single source of PM2.5 air pollution in the U.K is domestic wood burning, which is said to produce three times as much pollution as road traffic. The situation is similar across Europe. Only 8% of the population use wood burners New wood burning stoves are said to be more environmentally friendly but they still emit more tiny particle pollution than an HGV truck. The ecodesign standard developed by the EU allows wood stoves to emit 375 g of PM2.5 for every GigaJoule of energy produced. By contrast, an HGV can only release 0.5 g per GJ. HGV have filters and catalytic converters that capture / reduce pollution. The burning of wood in stoves involves many factors, including air flow, fuel quality / dryness and the amount of fuel being burnt. Full details of the European Environmental Bureau report “Where there's fire, there's smoke. Emissions from domestic heating with wood” can be found here . Bees, weather and disease. It is well known that weather has a direct effect the foraging ability of honey bees, now it is known that weather / climate also affect the incidence of disease in hives. A study undertaken by Newcastle University has revealed infection / disease in hives is affected by climatic variables. For example, varroa mite infestation increased as climatic temperature increased, but was reduced during heavy rainfall and wind. Full details of this investigation can be accessed here.
woodlands web updates 10.
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 .
Woodlands Web updates 9
Bark beetles. The blog has reported on bark beetles, and efforts to curtail their spread / damage. Now comes some hopeful news. Scientists have mapped the entire genome of the Eurasian spruce bark beetle. This could pave the way for new avenues of research into bark beetles and better means of pest control. Outbreaks of the beetle can lay waste vast areas of spruce forest, One significant finding is that this beetle has an unusually large number of genes (and therefore enzymes) that help to break down the cell walls of plants. However, whilst it has many genes for breaking down cell wall components, it does not have a similarly high number of genes concerned with the removal of toxins - such as the resin, from the wood it ingests. Now that the genetic make up of the beetle is known, it might be possible to turn off particular genes (using what is termed RNA interference), allowing for a highly specific pest control measure. Researchers at Lund University (Sweden) have identified the special receptors on the antennae of the bark beetle, and the pheromones (ipsenol and ipsienol) that they respond to. It is hoped that this might allow the development of environmentally friendly control measures - through disrupting their pheromone communication. This might be achieved by finding a chemical that binds to the receptors even more strongly than the pheromones. Pollinator decline. The Synthesis Centre for Biodiversity Sciences (Stellenbbosch University) has produced a report about the loss of pollinators and the possible effects on flowering plants. Drawing together the information from hundreds of different published research papers, it is estimated that some 175,000 plant species (roughly half of all flowering plants) rely to a greater or lesser extent on animal pollinators. In fact, a third of flowering plants would be unable to produce seed without pollinators. Since so many wild plants are reliant on pollinators, the decline / loss of pollinators will affect many natural ecosystems. Without pollinators, certain weeds and other plants that do not depend on pollinators may have a greater opportunity to spread - with less competition. Fires. Forest fires have been much in the news in recent years. Wide scale fires have been recorded in the United, States, Sweden, Russia and Australia. Drought is a significant factor as material on the forest / woodland floor dries out and combustible material accumulates. In some areas, the accumulation of combustible material may be associated with changing nomadic practices and declining pastoralism. Pastoralism is based on livestock production [e.g. raising of cattle, sheep, goats, even camels]. Such animals and indeed wild ones graze on vegetation so that combustible material is reduced, and to a degree natural fire breaks form. So, one strategy to mitigate the risk of fire in forests / woodlands is ‘targeted grazing’ by either domesticated animals or indeed wild ones.
Woodland web updates- 8.
Migrating hoverflies. Hoverflies are important pollinators, plus they also act as important predators of crop pests such as Aphids. Some hoverflies (like the pied and yellow clubbed hoverflies) spend the summer in the U.K. but then fly to the Mediterranean or North Africa come the autumn. They begin these migrations on sunny days but simply flying towards the sun would take them on a rather long winded route. A study by a research team at Exeter University suggests that they are able to account for the sun’s movement using their circadian rhythm - an internal clock. If the circadian rhythm of the hoverfly is disrupted, then so is its flight path. Migrating cuckoos. Like many other birds, cuckoos are in decline. Some time back, the BTO set up a research unit to learn more about the decline and behaviour of cuckoos. The work of this group has revealed details of the cuckoos’ migration routes and its winter homelands. Cuckoos have two routes out of the UK : They migrate out south west via Spain and Morocco - the WEST route, or They take a south east route via Italy and the Balkans (the EAST route) but Both routes ultimately converge on the Congo Basin in Central Africa. However, the birds that take the WEST route leave some eight days later than those taken the EAST route, but were more likely to die en route. Most of the mortality of the birds occurs in the European section of the migration path. This may be a reflection of the status of their stop-over sites. Problems might include : Habitat change, droughts and wildfires Decline in food sources (e.g. large moth caterpillars). A lot more detail / information on this project can be found here. VOC’s The air around us is a mixture of different gases / particles / and aerosols. An aerosol is itself a ‘mixture’ of very small particles (solid or liquid) in air. These particles can come from a variety of sources :such as volcanoes, cars, trucks and wood fires. Examples of aerosols include mist, cigarette smoke, fires volcanoes car exhaust fumes. Some trees and plants also release volatile organic compounds (VOCs), for example Pine trees release alpha-pinene. Recent research has established that these volatile compounds / vapours are not only responsible for the characteristic scent, but are also important in the formation of aerosols found in the air in and around such woodlands and forests. Atmospheric aerosols scatter and absorb light, and also influence the formation of clouds, though these processes are not fully understood. Recent research by the University of East Finland has showed that biogenic aerosols (formed from VOCs) can reduce the amount of solar radiation that reaches the earth’ surface. They help scatter the radiation back into space. These biogenic aerosols increase the number of cloud droplets and make the clouds more reflective.
Woodlands web updates 7
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.
Woodland web updates 6.
Pesticides problems. The effect of pesticides on bees and bumble bees is now well documented. However, the combined effect of different pesticides is less well known. If pesticide A is known to kill 10% of the bees in an area that has been treated, and pesticide B kills another 10% then it might be reasonable to assume that 20% of the bees would be killed - IF the effects are additive. However, evidence is beginning to indicate that the effects of the pesticides is more than the sum of the parts - the pesticides work together / synergistically. Pesticide formulations that are sold to farmers are often ready mixed ‘cocktails’ so exposure to more than one pesticide is often the norm, so it is important that these co-operative effects are understood and known. Honey bees have been affected by not only pesticides but also varroa. Varroa is a mite, which lives and feeds on honeybees and their larvae. Fortunately, bees have complex hygienic behaviours, for example, removing dead larvae or pupae. Research indicates that honey bees are modifying this behaviour to deal with varroa mites. Helping pollinators Researchers at the University of Freiburg have recently published work establishing the importance of semi-natural habitat regions next to orchards and other agricultural landscapes for pollinators. Such areas (ditches, banks, overgrown fences etc) help ensure that flowers (and therefore nectar and pollen) are available over a significant period of time. This is important for pollinators such as hover flies, solitary bees, bumblebees etc. as nectar / pollen provided by crops is only available for a short and limited period. Such areas are also important for overwintering, nesting sites, providing food for larval stages etc). Their work focused on orchards near Lake Constance in Southern Germany. Soil remediation with lupins. There are many sites around the world where the soil is contaminated with metals (such as arsenic) as a result of past mining / industrial activities. Such arsenic contaminated soil might be ‘revived’ by using the natural mechanisms that some plants have evolved to deal with certain contaminants. The white lupin (Lupinus alba) is an arsenic-tolerant plant that might be a candidate for phytoremediation of soil. The tolerance of the white lupin to arsenic is thought to be due to the release of chemicals by the roots into the soil. Staff at the University de Montréal placed nylon pouches close to the roots to capture the molecule released. The chemicals were then analysed to see which could bind to the arsenic (phytochelatins). Phytochelatins are known to be used within plants to deal with metals but here they seem to be used externally. Quite how they work is yet to be determined.
Woodland web updates (5)
Humidity and bumblebees Recent research at the University of Bristol has shown that bumblebees are sensitive to the humidity of the air that surrounds flowers. Being able to detect this sensory information affects the bees’ behaviour. Just as bees learn to recognise patterns, colour and the scent of particular flowers so they can distinguish humidity patterns. How effective these humidity patterns are will depend on the immediate micro-environment of a flower - which may be affected by climate change. Full details of this work can be accessed here : Willows and waste water Read more...
Woodland web updates 4
Beavers Two decades after were first returned to the UK, in Scotland, and 400 years after the species was hunted to extinction in Britain, counties across England and Wales will also become home to new beaver families. Beavers were hunted to extinction in the UK some 4000 years ago. A number have been reintroduced in Scotland and the South West, but this year should seen more re-introduction in Wales, the Isle of Wight, Derbyshire and Nottinghamshire. It is hoped the beavers’ activities will help restore/create wetland habitats, boosting biodiversity and reducing flood risks. Further details of these reintroductions can be found here. Peatlands As the woodlands blog has reported, peatlands are often under threat, for example, by fire. The Wildlife Trusts has called on the Government to do more to protect and restore our carbon rich habitats. The peatlands of the UK are estimated to store 3.2 billion tonnes of sequestered carbon - more than UK woodlands. Greening cities. London is to introduce a green space system in the coming months - termed the Urban Greening Factor (UGF). The Green Space Factor is an innovation of the City of Berlin in 1994, The plan calls for the various boroughs to implement urban greening practices. Ideas behind the plan have also come from the Swedish city of Malmö. Here, the Western Harbour (20-minutes from Malmö’s centre), was essentially 175 acres of contaminated soil and deserted docklands, subsequent to decline of the city’s shipbuilding industry. But now, it has been redeveloped with new apartment blocks - each of which is complemented by a green space area. There are parks, social courtyards and meeting spaces which offers beds planted with a native herbs and wildflowers. There are also stormwater drains and ponds that offer opportunities for wildlife. The impact of the road network. Our road network is extensive. There are nearly 700,000 km of road across the UK, which cover some 0.8% of the land. Roads permeate nearly every part of the country. Roadless areas are in short supply; they are mainly upland regions (peat bogs, moors, heathland and grasslands). Pollution from roads can take many forms Light pollution, Noise pollution, Heavy metals, Nitrogen oxides Particulates (PM2.5 & PM10) Whilst high levels of pollution are localised and associated with the busiest roads, a recent study (by researchers at Exeter University and the CEH) suggest that low levels of pollution from road networks are pervasive, and may extend over 70% of the land area of the UK. As the woodlands blog has reported, hedges can help block pollution to some degree and this has been substantiated by work done by Dr Tijana Blanusa et al at the Royal Horticultural Society. They investigated the effectiveness of hedges in ‘soaking up’ pollution, comparing different types of shrubs/trees - such as hawthorn and western red cedar. They found that on roads with heavy traffic that a species of Cotoneaster (franchetti) was 20% more effective than other species; though shrubs with ‘hairy’ leaves were generally effective in ‘trapping’ particulates.