Blog - Climate Change
Trees in trouble ?
A lot of research work now focuses on the resilience of woodlands and forests in the light of climate change, that is their ability to cope with conditions like drier, hotter summers and/or warmer/wetter winters. It has generally been assumed that trees at the limit of their range in dry regions would be most affected by climate change (with rising temperatures and less water). However, a major study of some six million tree annual ring samples, (involving 120+ species) coupled with analysis of historical climate data has shown that trees in drier regions show a certain resilience to drought. Trees seemingly become less sensitive to drought as they approach the edge of their range. Trees in wetter climates are less resilient when they experience drier conditions or drought. It seems probable that many species in wetter woodland and forest ecosystems will face significant challenges if the climate does move to a drier and warmer state. Assisted migration may be needed. One idea is to ‘exploit’ the genetic diversity found at the edge of a species range. The slow natural migration of trees may not be able to keep pace with the speed of climate change. Full details of this study by the University of California can be found here : Drought sensitivity in mesic forests heightens their vulnerability to climate change The effects of climate change have become very clear in recent times. This last year witnessed:- Record breaking wild fires in Canada, with the smoke extending across to the East coast of the States. [caption id="attachment_40597" align="aligncenter" width="675"] Canadian forest fire[/caption] Heat waves in parts of America , for example, Phoenix (Arizona) suffers the best part of a month with temperatures of 43oC. Parts of the North Atlantic Ocean saw unprecedented temperatures The global temperature in July was 1.5oC above the pre-industrial average, September saw temperatures 1.8oC above the pre-industrial average. Parts of Chile and Argentina saw a ‘heatwave’ in the middle of their winter. It is clear that ‘unchartered waters’ lie ahead.
Wildlife in Scotland
NaturScot is Scotland’s nature agency. It monitors and reports on all aspects of the natural environment. It has published a report on its terrestrial bird breeding species and it is a somewhat mixed report. Some of the most ‘famous’ species associated with Scotland, such as the black grouse have declined significantly during the period of study (1994 - 2019). The grouse population has halved, and the kestrel, greenfinch and lapwing populations are also in decline. Woodland populations of Capercaillie have also fallen. The largest grouse in the world, the capercaillie was once widespread but suffered local extinction in the eighteenth century and was reintroduced in the C19th. It is now only found in old pine forests and mainly in the Cairngorms National Park. The Capercaillie are now red-listed and protected in the UK. [The Pine Marten which feeds in part on the eggs of game birds was almost lost in the nineteenth century, due to farmers and gamekeepers trapping them.] The fall in bird numbers has been associated with changes in climate, notably warmer and wetter weather coupled with extreme events (such as flooding and heat waves). Whilst some species have suffered as a result of the changing weather, others seem to have prospered, including some that do not ‘traditonally’ make their way to Scotland. The great spotted woodpecker is one such species, its numbers have increase by 500%, bullfinch and red numbers have also increased. Gold finches and magpies are now more common on farmlands in Scotland. various measures could help offset some of these declines,.such as the diversification of woodland (more tree species) restoration of peatlands Creation of habitats on farmland legal predator control deer exclusion to allow regeneration removal of deer fencing, (where feasible) as capercaillie and black grouse are known to fly into this and injured as a result. One example of the benefits of deer fencing is to be seen in the Glen Lyone woodlands. Historically, this area was part of the royal hunting grounds of Cluanie and was home to capercaillies, wildcats and lynx. Nineteenth century maps show a significant area of woodland, but by the 1990’s less than a hundred of the ancient pines were left. The oldest pine in the area dates back to the C14th century, and many others are several centuries old. However, the area was heavily grazed by deer, which reduces regeneration as young seedlings / saplings get eaten. Now “Trees for Life” have erected new deer fencing, which hopefully will allow natural regeneration of pine forest in the area. Calendonian Forest once covered much of the Highlands but now less than 2% of it survives. Full details of this project (and a video) may be found here ; https://treesforlife.org.uk/scotlands-oldest-wild-pine-saved/
Woodlands Web Notes : 30
Willow bark and the covid virus. The Covid pandemic created great strains on health and business services, and the virus continues to impact society in many ways. It is not surprising that there is an ongoing search for anti-viral agents. Finnish scientists have found that willow bark may have a role to play. Willow bark has been used as a natural medicinal product over the centuries as an effective agent to treat pain and inflammation. The anti-inflammatory properties of the bark are generally ascribed to salicin, which was to lead to the development of acetylsalicylic acid, that is aspirin. The Finnish scientists ground up the willow bark in hot water and then sieved it to create an ‘extract’. This solution was then added to a number of cell cultures that were exposed to different viruses (enteroviruses, a seasonal coronavirus and SARS CoV2). They then monitored the viral activity, cell infection and viral replication The extract had an effect on all of the viruses. In some cases, the extract affected the envelope of the virus (a structure surrounding the viral genetic material) so the viruses essentially broke down, whereas others were prevented from releasing their genetic material and reproducing. Specifically, though the Covid-19 virus could enter cells when treated with the extract, it could not reproduce once inside. The research team analysed the extract’s chemical composition and tested some known constituents of bark but concluded the success of the extract probably resulted from the interactions of different biologically active compounds. Compounds in the extract included many complex chemicals (for example, hydroxycinnamic acids, salicylates, flavonoids, flavan-3-ols, and proanthocyanidins (polyphenols). Further work will focus on the role / interactions of these various compounds. The Hazel Dormouse in peril. The numbers of the hazel dormouse have fallen dramatically since the turn of the century. The dormouse has disappeared from Staffordshire, Northumberland and Herefordshire in the last few years. This loss is attributed to The destruction / fragmentation of their habitats Poor management of woodlands and hedgerows, leading to a loss of diversity / niches Rising deer numbers, feeding on saplings and shrubs Extreme weather patterns may also play a part Captive-bred dormice have been re-introduced to some 25 sites in 13 counties across the country, sadly nine of these reintroductions were not successful. Dormouse bridges have been created to enable the animals to move between areas dissected by major roads (such as the M1), others are planned. The dormouse (Muscardinus avellanarius) is a nocturnal animal and lives mainly in deciduous woodland, it feeds among the branches of trees and shrubs. the dormouse rarely descends to the ground. It feeds on a wide variety of 'foods' ; flowers (nectar and pollen), fruits (berries and nuts), certain buds and leaves and some insects, such as aphids and caterpillars. The hazel dormouse is regarded as a ‘flagship species’, that is to say, if the dormice are thriving then it is likely that other species are too from butterflies to birds such as the nightingale. Dormice are currently assessed as ‘Vulnerable’ to extinction in Britain under IUCN Red List criteria, but recent studies suggest a classification of ‘Endangered’ might be more appropriate. Certainly, their future is uncertain. Detailed information on the hazel dormouse is available at PTES (note this link opens a PDF). Their report details the state of hazel dormice in 2023. zsaqwa https://youtu.be/4u-yMkXOuTY Changes in the Boreal Forests. Boreal forests encircle the northern reaches of the Earth, lying just below the treeless under of the Arctic. These forest cover large areas of Alaska, Canada, Scandinavia and Siberia. These forests contain billions of trees, most are conifers but birch, poplar and aspen may also be found. The trees (and soils) contribute significantly to the cycling of carbon in nature, absorbing carbon dioxide in photosynthesis. They are also home to many species of migratory birds, plus predator species such as lynx and brown bears, and wandering herds of moose. Due to the remoteness of these forests, they have remained (until relatively recently) unaffected by human impact. Now these forests are warming at a rate above the global average. This has a number of effects: In the southern parts of the boreal forest. Conditions are becoming too warm for cold adapted trees; their growth is slowed and they may die. With the warming comes increased dryness, which leads to water stress and increased risk of insect attack / infestation. The dryness also means that forest fires are more likely and occur with increased ferocity. This year, the fires in Canada have been particularly extensive and damaging. Some 18.5M hectares went up in flames. The plumes of smoke spread far and wide. [caption id="attachment_40597" align="aligncenter" width="675"] Canadian forest fire[/caption] Scientists are now using satellites to track changes in the extent of the boreal forests. If trees are being lost on the southern edge of these forest, then it might be expected that the northern limit for tree growth might change. Indeed, there is some evidence for this in Alaska where young Spruce are now growing some 25 miles beyond the previous tree line, moving into the ‘treeless tundra’. It may be the loss on the southern edge is compensated by extension of the most northern parts of the boreal forest, but it is not clear whether tree can ‘move’ at the rate of climate change.
The short lives of many urban trees
The woodlands blog has reported on urban forests, the trees in our cities, lining our roads and in our gardens. This green infra-structure in our towns and cities provides a range of economic, environmental, and social benefits. The importance of green, leafy spaces was emphasised during the early days of the Covid pandemic, helping with mental and physical wellbeing of many people. Urban trees offer Valuable habitats for wildlife and can provide biological corridors / stepping stones that enable birds and other animals to move through the urban environment. Shade and cooling in streets and parks. They can help reduce the risk of flooding, allowing more water to enter the soil rather than running off hard surfaces of tarmac and concrete. The capture of pollutants, improving local air quality by capturing fine particles from the air (mainly through deposition on leaf surfaces). Trees and shrubs seem particularly effective in removing ozone. Through their photosynthetic capacity, trees can take up carbon dioxide into organic form - carbon sequestration. The amount of carbon taken up by London’s urban forest each year has been estimated at 77,200 tonnes. However, recent studies suggest that many urban trees are under threat : Trees are subject to heat stress as many cities experience the heat island effect, the ambient urban temperature is significantly above the surrounding countryside. Many struggle to get sufficient water as they are planted in small square of soil and surrounded by tarmac, concrete or paving stones. Soil compaction is often an issue, affecting water permeability. They may experience an ‘excess of nutrients’ - due to dog’s urine, this is a source of urea and other nitrogen compounds. Once planted, young trees may not receive after-care / management. This point is significant. Many trees die within the first few years of planting. In Boston (USA), some 40% of trees are dead within seven years of planting. Similar figures are true for New York. Both rural and urban trees suffer significant mortality when young but whereas the death rate of rural trees tend to decrease after a few years - urban trees are more likely to die as they age. [caption id="attachment_40541" align="alignleft" width="300"] Young urban tree[/caption] There is a struggle to reach maturity. Most trees need two or three decades to offset the carbon emissions associated with their planting / maintenance etc, and they then sequester carbon at a significant rate. Work at Boston University (in Professor Lucy Hutyra’s lab) and Harvard has focused on the problems that urban trees are facing, and another issue (apart from those mentioned above) has been identified - the microbiome of the root [that is the variety of micro-organisms that surround / inhabit the root tissues]. Urban trees seem to have fewer symbiotic fungi in their root systems when compared to rural trees. Roots often develop mycorrhizal associations with fungi. Such systems allow the roots to access more water / minerals and in return the tree ‘offers’ the fungal network a supply of carbohydrates. Jenny Bhatnagar (Harvard) has investigated the soil microbiome in eight different plots, some urban and some rural in Massachusetts. Interestingly, the investigation found that whilst there were more fungi in urban plots, they ‘seemed more reluctant’ to establish symbiotic associations with the roots of the trees. This failure could be due to the excess nitrogen / nitrates in the soil (from animal urine / faeces?). When there is an excess of nitrogen available, trees tend to dispense with their fungal partners. The hotter temperature of urban soils might 'favour' a bacterial population (some bacteria ‘fix’ nitrogen). [caption id="attachment_40526" align="alignright" width="300"] Once, there was a cherry tree ...[/caption] It is not clear as yet why so many urban trees fail. It could be that the loss of the symbiotic fungi renders the trees more susceptible to certain disease-causing microbes. The hotter and drier soils at the edges of fragmented forests have more pathogens and not so many symbiotic fungi. A number of simple aftercare / management measures would help young trees to establish : Watering the trees in their early years Preventing soil compaction to allow water to percolate, and oxygen to diffuse to the roots. Mulching around the tree base (helps water availability and slows nutrient input from urine etc.) An interesting article on mycorrhizae and urban trees may be found here. [caption id="attachment_40537" align="alignleft" width="220"] Olive[/caption] The importance of soil micro-organisms is also indicated by research in Australia, where shrublands / woodlands have been invaded by African olive trees. The olives have disrupted the partnerships between the Acacia trees (hickory wattle) and symbiotic soil bacteria (Rhizobia ssp). This is another symbiotic association, where the partners exchange materials for mutual benefit, Where the Olives have grown, the Acacia have problems establishing root nodules with the bacteria. To restore these scrublands, a full understanding of the soil / root microbiome will be important. Full details of this work can be found here. Postscript : In today’s Guardian (03/11/2023), Helena Horton’s article “Ministers should target tree survival ‘rather than planting’” reinforces the points made in the blog about the early mortality of young trees - urban or rural. Increasing woodland cover will only occur if young saplings survive.
After-effects of forest fires.
In 2018, the blog reported on the extensive fires in Sweden, a country noted for its forests and woodlands, which cover approximately half of the country. Once the trees were mainly broad leaved species, but then oaks and alders began to decline. By the middle of the twentieth century, Spruces and Pines were dominant. This was mainly due to forestry management, to produce wood for fuel, charcoal [used in iron smelting], potash, tar and timber (for building). Fires burnt from the extreme north down to Malmo in the south. These fires affected some 20,000 hectares and destroyed woodlands valued at [circa] £50 million. Now work by scientists at Uppsala University, the Swedish University of Agricultural Sciences (SLU), and the Swedish Meteorological and Hydrological Institute (SMHI) have examined the effects of the fires (of 2014) in the Vastmänland province, where the fires were ferocious, burning down into the soils. They have found that the 'forested areas' continued to lose carbon for several years after the fire, and that nitrate and phosphate input to streams and rivers increased after the fires. This spring and summer have again witnessed intense and widespread fires across the Mediterranean region, Canada and the United States. Fires are a problem not only because of their immediate destructive potential, but because they result in the release of carbon dioxide - which further contributes to global warming and climate change. The United Nations Secretary-General said recently “The era of global warming has ended; the era of global boiling has arrived.” Data on these fires is not available as yet, but studies of the boreal fires in 2021 suggest those fires released some 1.76 billion tonnes of carbon dioxide into the atmosphere. The fires contributed nearly one quarter of world wide carbon dioxide emissions from fires in that year. [caption id="attachment_35352" align="aligncenter" width="650"] Woodland recovering from a fire[/caption] Boreal forests store roughly twice as much carbon in their trees and soil as tropical forests. These forests (often referred to as the Taiga) surround the Arctic Circle and research suggests the Taiga is warming faster than the global average, so areas like Northern Canada and Siberia now experience more heat and drought than in the past, and consequently are more likely to suffer from fires. Clearly, when there is a fire, carbon dioxide (and many other carbon compounds eg soot / small particles) are released by the burning of the trees but there is also the effect of fire on the soil and its organic content - the humus. Research indicates that during the fires in the boreal area some 150 tonnes of carbon dioxide may be released into the atmosphere per hectare. Furthermore, even after the fire, carbon continues to be lost from the soil. It may take some three years for carbon uptake by the soil to be recorded. Fires also lead to the rapid loss (leaching) of nutrients (e.g. phosphate) to local lakes and rivers - as there is little or no vegetation to absorb the nutrients. Rainfall is not intercepted by vegetation and so the flow of streams increases ( sometimes by 50%). A research paper produced by the Desert Research Institute (in Nevada) has indicated that smoke from the burning of pines has the effect of making soil particles more water-repellent. This repellency of smoke-affected soil particles could help explain the increased flooding, erosion, and surface runoff in fire damaged areas.
Losing woodlands and forests.
Across the world forests and woodlands are under threat, suffering fragmentation and shrinkage. This is not good news for the plants and animals that rely on these habitats for their survival. In a large forest or woodland, animals can move around over considerable distances in search of food / partners - without having to leave the area that supports them. Similarly, plant seeds when dispersed are more likely to find the micro-climate that they need for germination and subsequent growth (humidity, shade, soil type etc). Some species have very ‘exacting’ requirements that can only be met in the heart of a forest or woodland. For example, there is a frog that is restricted to undisturbed mountainous forests in Borneo. Sadly, recent surveys suggest that many forests continue to suffer from fragmentation / loss of area. The two main reasons for this loss are : clearance for agriculture (palm oil plantations etc) - this has mainly affected tropical and sub tropical area. Sometimes fires are used as a deliberate ‘tool’ to clear an area of forest so that the area can then be used for agriculture. wild fires - these have affected the Boreal Forests but also regions of the Amazon Basin. In areas like Siberia and Canada, drought and high temperatures have lead to extensive fires. (Zombie fires are underground peat fires that smoulder in the winter months but reignite when the ground dries in the Spring or Summer.) Recent times have seen extensive fires across Siberia, Canada, parts of the West Coast of America and Australia. Woodlands have experienced fragmentation due to the expansion of agriculture, the building of motorways & roads, and the expansion of housing. Wild flower meadows have suffered even more dramatically - with some 90+% lost in relatively recent times. Obviously fires are devastating locally, killing vast numbers of animals and plants. Fire also destroys the organic content of the soil and its complex microbial population. The plumes of smoke released by fires (such as those seen in Canada and Australia) spread extensively. The Canadian fires (883 fires raging at one point) left mile after mile of blackened forest, and forced hundreds of people from their homes. The smoke spread far beyond Canada’s borders, as far away as parts of Europe. New York City was ‘bathed’ in an ‘orange haze’ and experienced a hazardous level of air pollution. The plumes from such fires are rich in black carbon soot. The soot particles absorbs solar radiation, keeping heat in the atmosphere. Recent analysis of smoke plumes indicates that there is also ‘dark brown carbon’. This consists of a previously unknown type of particle and whilst these particles absorb less light per particle than black carbon, they are approximately four times as many brown carbon particles in wildfire smoke (compared to black soot particles). There is also the suggestion that these brown particles retain capacity to absorb solar radiation for longer.
The DiversiTree Project and Woodland Diversity
Rapid onset climate change, and the spread of new pests and diseases are creating unprecedented challenges to the long-term survivability of UK woodlands. This looming threat is becoming ever more tangible, and the need for strategies of resilience building is urgent. Promoting diversification within and amongst woodlands has been identified as one such strategy with the potential for significant, positive impact. DiversiTree is a UKRI-funded project led by the James Hutton Institute which is measuring the impact a more diverse mixture of tree species has on building resilient woodland ecosystems, as well as how woodland managers and others understand woodland diversity, and what they are CURRENTLY doing to promote resilient woodlands. The project also hopes to generate practical advice and results which managers can use to make better informed decisions regarding the species mix of their woodlands, especially with regard to conifers. A key question which often accompanies discussions of woodland diversity is the planting of non-native species within British woodlands. The DiversiTree project is taking an evidence-focussed approach to its assessment and are investigating how ecological resilience interacts with woodlands with different priorities or objectives and what this might mean for the longer-term ecological sustainability of the forests of the UK. In actuality, many native woodlands are rather species poor, and could potentially benefit from a period of managed diversification with native species, non-natives, or a mixture depending on local objectives and context. What is critical here, is understanding the ecological role ANY tree can serve in a complex landscape, and planting in a manner which enhances and strengthens a woodland’s biodiversity. If you’d like to learn more about our work and keep updated with our progress, please follow us on Twitter @DiversiTree_UK (https://twitter.com/DiversiTree_UK?s=20) or email [email protected] with any questions. Seumas Bates (Environmental Anthropologist, Bangor University)
Where do butterflies come from?
An obvious answer to this question would be - caterpillars. But when did butterflies first appear? There are now some 160,000 species of moths and butterflies -worldwide. Seemingly, they appeared some 100 million years ago - in North America. They evolved from nocturnal moths in the period when flowering plants were undergoing a major expansion (in the Cretaceous period). Butterflies may have become diurnal to avoid predation by bats, or it may have been to take advantage of nectar production and availability [using the proboscis]. The butterflies and their caterpillars were able exploit the diverse range of food resources that these ‘new’ plants offered. Butterflies moved out from North America to South America and then on to other parts of the world, though they probably did not arrive in Europe until some 17 million years ago. The evolutionary expansion of the butterflies has been investigated by researchers at the University of Florida; they analysed the genetic makeup of many species (from 90 countries). They were able to build up a picture of the relationships between the various groups of butterflies and also determined their evolutionary point of origin. They also catalogued the plants eaten by the caterpillars and it was found that some two thirds of butterfly caterpillars feed on plants from the legume family (the Fabaceae - peas and beans). It is probable that the first butterfly caterpillars also fed on these plants. Research at the Georgetown University in Washington DC suggests that larger species of butterfly are ‘coping’ better with higher temperatures, associated with global warming. Bigger wings seem to offer a greater range of movement and the opportunity to find new and suitable habitats. Smaller butterflies are not faring so well. The study involved an analysis of the range of some 90 North American species between 1970 and 2010, during which period the monthly minimum temperature increased by 1.5oF. Others have analysed the butterfly collections at the Natural History Museum, using digital technology. The Natural History Museum’s British and Irish butterfly (and moth) collection is probably the oldest, largest, and most diverse of its kind in the world; some of the specimens date back over a hundred years The measurements of the various specimens were paired with the temperature that the species would have experienced in its caterpillar stage. It was found that for several species that the adult butterfly size increased as the temperature increased (during late larval stage). So, it may be that we will see a gradual increase in butterfly size as temperatures increase with global warming. Join the Big Butterfly Count ? Between Friday 14th July and Sunday 6th August , the big butterfly count will take place. For full details visit : https://bigbutterflycount.butterfly-conservation.org/about Thanks to Angus for images.