Blog - Climate Change
Too hot, too dry.
The UK has experienced some of the highest temperatures ever recorded in recent weeks, and in some parts of the country this has coincided with very low levels of rainfall. It was the driest July on record for East Anglia, southeast and southern England, according to provisional statistics from the Met Office. July was also the first time the UK exceeded temperatures of 40°C: on 19 July during an intense heatwave. These conditions are not without their effects on wildlife. Whilst warmth can accelerate plant growth and development, and also speed up insect life cycles, but the recent very high temperatures have significant effects, for example: Drying of the soil As the soil dries, so earthworms burrow down deeper. Insects, woodlice, spiders, etc avoid the surface of soil, hiding in litter so birds like song thrushes, robins and blackbirds struggle to find something to eat. Consequently, they are less likely to produce a second brood of chicks. This scarcity of invertebrates also affects ground feeding mammals, like hedgehogs (and badgers in more rural locations). Wetland areas dry out; for example grazing pasture that floods in winter - like the Ouse Washes. This makes it difficult for birds to find food. Lack of water for plant growth Reduced rainfall and high rates of evaporation from the soil (and plants) mean that there is considerably less water available for plant growth. The growth of leaves is reduced so that there is less material for caterpillars and other insects to eat. With fewer leaves , there are also reduced surfaces for butterflies and other insects to lay eggs. High temperatures High temperatures and lack of water can affect many animals (including us). Rivers are running at very low levels and some have more or less disappeared. DEFRA’s latest assessment of principal salmon rivers, such as the River Test shows that 74% of rivers in England are now ‘at risk’. The Environment Agency has noted the flow rate in the Waveney as 'exceptionally low', while other rivers in East Anglia like the Great Ouse the Yare, and the Little Ouse are described as 'notably low'. The young of birds like swallows and swifts are at risk of fatal overheating (the young and old of various species are often more susceptible to heat stress). Bumblebees cannot forage at high temperatures. Their bodies are covered with ‘hairy coats’ so they can fly when it is cool; but these become a burden in hot spells.High temperatures also shorten flowering time, and hence the availability of pollen and nectar for pollinators (bees, bumblebees, overflies, butterflies). Wild fires. [caption id="attachment_35352" align="aligncenter" width="650"] Woodland recovering from a fire[/caption] High temperatures increase the risk of wild fires, especially on moorland and heathland. These fires can spread quickly and over wide areas. Young chicks (e.g. Dartford Warblers), eggs, snakes, lizards, small mammals, dragonflies and butterflies are lost. Accumulated nutrients and stored carbon are lost from the ecosystems. The site of Springwatch Wild Ken Hill in coastal Norfolk suffered an intense fire during the recent hot spell. The area is home to turtle doves, the grasshopper warbler and other rare birds. It is hoped that most escaped but mammals, reptiles and amphibians, late-nesting and juvenile birds may not have fared well. Grassland and woodland fires have also been reported at various sites across the country. The UK is not alone in facing these problems, Spain, Italy, Portugal, Greece, France and Germany have all lost many thousands of hectares to wildfires. [caption id="attachment_38699" align="aligncenter" width="700"] what was once was grass .....[/caption]
How does rewilding help climate change?
We are in the midst of a climate emergency: temperatures are rising, and in February 2022 the UN warned that more than 3 billion people are living in areas that are highly vulnerable to global warming, putting their lives at risk. Scientists suggest that rewilding could be one of the best climate solutions available to offset greenhouse gas emissions and to protect our lives and ecosystems. Rewilding involves restoring ecosystems and natural processes, and though at first it will require strict ecosystem management in order for it to be successful, the aim is that rewilding nature will allow it to then be able to ‘take care of itself’ and repair the damage made by humans. It’s estimated that restoring natural ecosystems could provide 37% of the greenhouse gas mitigation that’s needed for us to prevent the warming of the planet above 2 degrees celsius by 2030, so it should not be underestimated by national governments as a strategy to offset their emissions and restore the ecosystems of their countries. Ecosystem restoration Rewilding can restore ecosystems, allowing them to reach their full potential for fixing carbon, helping to offset greenhouse gas emissions through their own natural processes. Due to the fact that trees absorb carbon through the process of photosynthesis, it’s estimated that regenerating fully establishing forests will sequester 10 tonnes of CO2 per hectare from the atmosphere. Meanwhile, restoring peatlands (which store more carbon than the world’s rainforests, but of which 80% have been damaged by draining, extracting, burning and overgrazing) will allow them to once again reach their full potential of sequestering carbon. Damaged peatlands in the UK release 23 million tonnes of carbon CO2 (or equivalent) per year, which is more than all of the UK’s oil refineries combined; restoring them will reduce this significant strain on the environment. Restoring these ecosystems will also provide habitats for a large range of wildlife, which also play a crucial role in preventing climate change. The flora and fauna of an ecosystem are essential for its maintenance and conservation— they prevent catastrophic events like species’ extinction, flooding and wildfires. In fact, herbivores can have a massive effect on atmospheric carbon levels, so restoring their populations and allowing them to roam freely will mean they’re able to trample and compact soils and sediments, and increase the amount of carbon that’s absorbed and stored in plants, as well as impacting the natural growth of flora by redistributing seeds and their grazing. In the coming decades, as the effects of climate change worsen, reintroducing native plant and wildlife species will improve both the resiliency and carbon sequestering abilities of an area. It has also been shown that biodiverse environments are able to absorb more carbon, with each additional species introduced adding up to 6% in its total carbon stocks. Rewilding will benefit humans too of course, and not just in major ways (ie. protecting our livelihoods from the effects of climate change) but also by blurring the boundaries between the human and natural worlds, which will benefit our mental and physical health. There are also economic opportunities that can arise from rewilding, such as nature-based tourism. Where is rewilding happening? There are many rewilding organisations across the world and in the UK, several of which have undertaken successful rewilding projects, restoring the carbon sequestering capabilities and increasing the numbers of species in different areas. Rewilding Europe have identified that after a decline in populations of several wildlife species, such as beavers, elks, whooper swans, and white-tailed eagles, they are finally increasing again. The Serengeti went from being a major source of carbon emissions to a sink after the wildebeest population were restored, and now sequesters between 1-8 million tons of carbon every year. Rewilding has endless potential across the world, too: restoring forest elephants to their historic levels in the Congo basin could lead to it sequestering 85 million tons of carbon each year (the equivalent to France’s annual emissions) while rewilding and conserving the functional role of vertebrate and invertebrate species could supposedly magnify carbon uptake 1.5-12.5 times or more across terrestrial, freshwater and marine ecosystems. The finance and politics of rewilding In the UK, Rewilding Britain has been calling upon the government to make a bolder ‘financial and political commitment to nature’s recovery,’ including developing policy for an ‘economy-wide carbon pricing mechanism linked to carbon emissions’ in order to raise money to fund rewilding projects. Though the Prime Minister has pledged to protect 30% of the UK’s land and sea by 2030 to allow it to recover and rewild, Rewilding Britain has suggested that there is not enough of an incentive for industries that contribute most to greenhouse gas emissions in the UK, such as the agricultural industry, and that the UK government have only attracted 2.5% of the funding that would be needed for the mitigation of greenhouse gases in this country. Instead, they propose a ‘polluter-pays’ approach whereby there is a mandatory price attributed to carbon emissions that the polluter must pay (they suggest £40 per tonne which would yield a maximum of £17.4 billion per year), which could then be reinvested into rewilding and conserving the natural environment. There would also be annual payments made to those who make efforts to offset carbon by restoring landscapes according to how much carbon (or equivalent) each landscape has the ability to sequester; woodlands would be £413 per hectare; salt marshes £322/ha; peat bogs and heathlands £292/ha; ponds and lakes £404/ha; offshore ecosystems £161/ha; and species-rich grasslands at £204/ha, with the payments being capped at 1,000 hectares per individual. How to get involved in rewilding: Rewilding has the potential to make a significant contribution towards preventing the effects of climate change, but its full potential being reached relies on our international governments stepping up to the task of making sufficiently bold policy that incentivises farmers to restore landscapes, as well as businesses to pay the costs of their greenhouse gas emissions. The question is, how can the general public get involved in rewilding? There are lots of options available, whether that’s starting small by rewilding your garden by planting native wildflowers, to buying land with the intention of rewilding and conserving it, to volunteering for organisations such as Rewilding Europe, or writing to your local council to encourage them to leave roadside verges uncut. You might even consider providing funding for rewilding projects. Education about the rewilding benefits is also severely lacking, so raising awareness about how rewilding helps climate change is another way to get involved. No matter how we get involved, it will all contribute to the fight against climate change, so let’s get to it!
The plight of the bumblebee
We know that insects (especially, bumblebees, bees, hover flies) are the world’s top pollinators, and we also know from many reports that many insect species are in decline. Crops such as tomatoes, blueberries, peppers, cocoa, coffee, almonds and cherries are dependent on these pollinators. Climate change, increasing temperatures and extreme weather events are affecting plants and animals across the world, and it seems that social insects, like bumblebees, are particularly impacted. Research with bumblebee colonies (at Stockholm University) has indicated that if the colonies are exposed to higher temperatures (than normal) then the workers in the colonies were smaller. This decrease in body size could affect their foraging behaviour and the collection of pollen, which would mean less food brought back to the colony and reduced pollination of plants. Studies in the United States looked at some 20,000 bees (bumblebees, leafcutter bees, mason bees etc) along the Rocky Mountains, a region which is vulnerable to climate change. It was found that the larger bees (particularly bumblebees) and those that built nests with combs were affected most by increases in temperature. On the plus side, smaller (soil nesting) bees fared better. Bumblebees would seem to have a lower heat tolerance. The loss of bigger bees, which generally can fly and forage further may again mean reduction in long distance pollination (which promotes outbreeding in plant populations). One reason why hot or hotter weather affects bumblebees is that it influences the nectar that the bumblebees collect. The balance of the various micro-organisms (bacteria and yeasts) in the nectar changes. Whilst bumblebees are attracted to nectar with some microbes in it, a small change in temperature can speed up the metabolism / growth of the microbes so that they use up more of the sugar - with the result that it is less palatable / less nutritious for the bees. Experiments conducted at the University of California have shown that bees did not ‘like’ the nectar rich in microbes, nor a sterile one - with no microbes at all. There seems to be a 'happy medium' in terms of the composition of the nectar. There seems to be a growing consensus that climate change, increasing temperatures and extreme events are pushing bumblebees (in particular) beyond their physiological limits. [caption id="attachment_38081" align="aligncenter" width="650"] Bumblebee visiting foxglove[/caption]
The opening of the woodland canopy.
Certain woodland plants are found in the understory. Plants like wood anemones, woodruff and lungwort bloom early in the year. These plants make use of a ‘window of opportunity’ when the light levels are good as the tree canopy has not developed, the leaves have not yet expanded. They use this ‘window of light ‘ to flower. However, climate change is affecting many ecosystems - including woodlands. With warmer temperatures, leaf buds tend to open earlier and the leaves begin to expand. If the window for growth is reduced, how can the wood anemones and others cope ? [caption id="attachment_38093" align="aligncenter" width="700"] wood anemone[/caption] To investigate this question, scientists based the Universities of Tübingen and Frankfurt examined thousands of preserved herbarium specimens of early flowering plants, dating back over a hundred years. The sheets not only hold specimens collected when they were flowering but also have information on ‘when and where collected’. Each sheet is a a moment in time from over a century ago. Collectively, the 6000+ sheets allowed the scientists to establish historic flowering times of woodland plants over large areas of Europe. [caption id="attachment_38094" align="aligncenter" width="700"] Woodruff[/caption] The information extracted from the herbarium records revealed that plants like wild garlic and wood sorrel now bloom some six days early than at the beginning of the twentieth century. For each 1oc rise in (Spring) temperature, their lowering has advanced by more than 3 days. This means that they have gained time in the light - in an open canopy. Whilst they may have gained time, these early flowering plants are at greater risk of frosts. It may also be that their pollinating agents may not be around - unless they too have brought forward their development / life cycle. There is some evidence that such changes are taking place. Recent work at Wytham Wood (outside Oxford) has shown that blue tits have moved forward their egg laying to 'match' the development of the oak canopy, and the appearance of caterpillars (on which the young are fed). Essentially, the timing of the food chain has changed.. Hopefully, such changes will occur in different ecosystems across the country.
Spring is on the move.
In recent decades, signs of Spring have occurred earlier and earlier, indeed the early flowering of crocuses and daffodils in our gardens is one such sign. Now a detailed analysis of such ‘signs’ has been undertaken by using the information held in Nature’s Calendar. This is an enormous database * of records of seasonal changes; it has records of some 400+ species of plants, from trees, to shrubs and herbs. Nature’s Calendar includes records from organisations like the Royal Meteorological Society, plus those of scientists, naturalists and gardeners. Recording when things happen (such as when horse chestnut and ash trees come into leaf, or when the first swifts or bumblebees are seen) is known as phenology. These timings vary from year to year. Phenology is not a new discipline. One of the first phenologists was Robert Marsham, who recorded ‘indications of spring’ starting back in 1736. He catalogued some 27 different natural events on his family’s estate in Norfolk. In 1875, the Royal Meteorological Society set up a national recorder network. Nature’s Calendar includes thousands of these historical observations and enables scientists to look for trends and see if they correlate with changes in temperature, rainfall, weather phenomena. The research team from Cambridge University looked at FFDs - first flowering dates and temperature records. They found a difference in flowering dates from the 1750s and the most recent years of almost a month. Professor Ulf Büntgen has said that rising global temperature has brought Spring forward by several weeks. This raises concerns. For example, if a plant grows and comes into flower earlier in the year what happens to insects that are dependent upon it? For example, some bees collect from only one species of plant. Or to put it another way, suppose the plant flowers earlier but its pollinating agent (an insect such as a hover fly) is not about, has not emerged from its over-wintering stage? What if there is a ‘late’ frost? * Nature’s Calendar : The Woodland Trust joined forces with the Centre for Ecology & Hydrology to collate phenology records into Nature’s Calendar; this has some 3.5 million records- some going back to eighteenth century.
The loss of animal species, and the effects on fruit and seed dispersal.
Sadly, the world is losing species, both plant and animal, at a significant rate. Indeed, some claim that we are now experiencing the sixth mass extinction. In contrast to previous extinctions (the Permian extinction is thought to be due to an asteroid impact), the present loss of species is largely associated with a mix of direct and indirect human activities. These include :- destruction and fragmentation of habitats, Exploitation fishing stocks and hunting (think dodo), chemical pollution, invasive / introduced species, and human-caused global warming The loss of animal species has knock-on effects in terms of food chains and biodiversity. Plants are also affected as many rely on animals for the dispersal of their fruits and seeds. In times of global warming, it is essential that plants can reach new areas that are suitable for their growth. If not, they are stuck in areas where they may not be able to survive in the changed / changing conditions. This could mean that plant species are lost, together with the ‘ecosystem services’ that they provide (be it food, timber, carbon storage, flood mitigation etc). Seed dispersal is also important in terms of recovery from ecological disasters, like wildfires. Natural forest regrowth usually happens through seed dispersal. If an ecosystem is rich in species, it is generally more resilient to environmental change. The relationship between fruit / seed dispersal and animals has been significantly affected by the creation of roads, motorways, farms, and the development of cities - essentially habitat fragmentation. Animal dispersal is often associated with fleshy fruits. Whilst this is particularly true / obvious for many tropical fruits, it is also the case for many plants in temperate regions. Berries, hips and haws are dispersed by animal means, with birds being particularly important agents. Several pines produce large seeds and attract corvids such as nutcrackers and jays. The birds, sometimes called scatter hoarders, collect seeds and bury them in areas away from the parent trees but in habitats suitable for the next generation of trees Mammals also play significant roles. In Africa, elephants are important seed dispersers for numerous species; they have an extra-ordinary sense of smell and will search out ripe, fleshy fruits. Some seeds have been shown to be distributed 60+ kilometres from a parent plant. Not only this, but the journey through the gut of the elephant seemingly increases the chance of germination, and being deposited in the dung reduces the chance of the seed being eaten by beetles. Some monkeys in South and Central America eat as many as fifty different types of fruit in a day. carrying some off in their stomachs and dropping others to the ground. In Britain, as part of their diet, foxes will eat various wild fruits, like blackberries; squirrels eat nuts; and mice / voles eat grass and other seeds. Even invertebrates, like ants, disperse seeds. This may be through the activity of harvester ants, which, like squirrels and other ‘gatherers’, forage the ground of the wood or forest (collectively) gathering large quantities of seeds and then transport them back to their nests / colonies. As they transport the seeds, some get dropped or lost on the way. Others may be ‘cached’ in or near the nest for later consumption but then are ‘forgotten’ or ignored. Some fruits contain seeds covered with a sticky substance as is the case of Mistletoe. When birds feed on the fruits, the seeds often stick to the beaks of birds. Then, they may wipe the sticky seed off on a branch; or it may be eaten and pass out in the bird’s droppings. The ‘glue’ (viscin) around the seed helps fasten the seed in place. Even humans carry seeds far away for plants, for example, by taking an apple on a picnic and throwing the core with its seeds into the bushes. Or seeds may transported in the mud sticking to boots and shoes, or indeed on tractors, cars or other machinery. The loss / extinction of animal species from any given habitat will sooner or later effect the plants. We are only beginning to fully appreciate the interdependence of life. The loss of any species - plant or animal - will undoubtedly have unintended and unforeseen consequences which can only be to the detriment of all life on earth.
Creating diverse woodlands and forests
We know that forests are important to all life on the planet. They have often been referred to as the ‘lungs of the earth’, a reference to the fact that they produce vast quantities of oxygen - which is essential for respiration for so many forms of life. They also take up carbon dioxide and ‘fix’ it into complex organic molecules - from starches, to cellulose and lignin. Thus, the carbon is locked away for months, years or even millennia. The equatorial forests of Brazil and Sumatra are species rich, incredibly diverse, but deforestation and the expansion of agriculture are threats to many biodiverse, forested areas across the world. As so many forests and woodlands have been felled, there is now a movement to plant millions and millions of trees (across the world) in an attempt to mitigate climate change and in the UK to increase our percentage tree cover from a pretty low base. Sadly, twentieth century forestry in the U.K was largely based on monocultures (for timber production). The trees planted were large stands or plantations of conifers - using Scots Pine, Larch and Spruce. These plantations not only lacked biodiversity, but were / are susceptible to wide scale pest infestation and extreme weather events. Woodlands and forests that have a diverse range of tree species are not only healthier but show greater growth and carbon fixation. They are more resilient. The diversity of trees ensures the each species accesses slightly different resources from the environment - from soil minerals, water and light. Diversity means that trees of the same species are less likely to be clustered together so pest and pathogen outbreaks are less common or less severe. One area that has undergone an extensive and diverse planting regime is Norbury Park Estate (near Stafford). Since 2009, over 100 different tree species have been planted, and the woodlands can now produce 1500 tonnes of new wood each year, and harvest 5000 tonnes of carbon dioxide from the air. Not only can diverse woodlands / forests fix carbon, supply harvestable timber but they also offer areas for rest and relaxation. Whilst it is not possible to plant an 'instant' forest or woodland, it is possible to plant a range of tree and shrub species that will in time grow and mature to form a diverse and species-rich area. As Charles Darwin said many years ago “more living beings can be supported on the same area the more they diverge in structure, habits, and constitution” [On the Origin of Species by means of Natural Selection, 1859] Managing woodlands for wildlife - see here. N.B. Opens a PDF.
Drought and pollinators
Climate change is affecting all parts of the world, from the melting of the ice caps in Antarctica, to droughts in Australia and California. On a more local level, we may see changes in our rainfall pattern. Certainly for many parts of the UK, it has been a very dry start to the Spring, coupled with some very cold nights. Cold and dry weather affects plant growth in significant ways. Warmth is needed for a plant’s enzymes (catalysts) to work, speeding up reactions and allowing growth. Similarly, if water is in short supply, growth is stunted; plants do not realise their full ‘potential’. They are smaller overall as is the number and size of flowers that they produce. Flowers attract visitors by colour, size and scent; or combinations thereof. Smaller and fewer flowers, in turn, have ‘knock-on effects’ for their pollinators - bees, bumble bees, hoverflies etc. The effects of drought on pollination has been recently investigated by researchers at Ulm University in Germany. They studied the effect of drought on field mustard (aka Charlock) : Sinapsis arvensis. This is an annual plant that is to be found in fields, waysides and field margins across Europe. It has bright yellow flowers, with four petals. It is visited by many different pollinators (it cannot self-pollinate). The researchers compared the number of visits by bumblebees (Bombus terrestris) to drought-stressed plants to well-watered ones. The data showed that as the number and size of the flowers decreased so did the number of pollinator visits. [caption id="attachment_21589" align="aligncenter" width="600"] Bumblebees also favour the teasels[/caption] The ‘attractiveness’ of the plants / flowers to pollinators was reduced, and it is possible that the smaller flowers were more difficult for relatively large pollinators (like the bumblebees) to ‘deal with’. If pollen movement is reduced, then fewer fruits / seeds will be set and (insect pollinated) plant populations could decline. The effects of reduced rainfall and water stress need to be considered alongside the declining number of pollinators. The reduction in pollen movement has lead some to speculate that it might lead to a selective pressure for self-pollination / self-fertilisation, with plants dispensing with the need for visiting insects. Other Woodlands blogs have reported on the falling numbers of insects / pollinators. Featured image : garlic mustard.