Blog - climate change
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.
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 .
In a previous woodlands.co.uk blog, Professor Dave Goulson (University of Sussex) has written about the problems that bees and bumblebees face. Recently, he joined with Clipper teas (who produce organic tea products) to again emphasise the problems that bees and other pollinators face, and to explain how our lives would be affected if they were to be lost. Bee, bumblebee and other pollinator populations are at risk or in decline. Professor Goulson estimates that there are some 6,000 different species of pollinating insects in the U.K alone, but they face risks as a result of Habitat loss Pollution Climate change Use of pesticides (insecticides, herbicides, fungicides) [caption id="attachment_36158" align="aligncenter" width="650"] Hoverfly foraging[/caption] Whilst it is true that insecticides such as neonicotinoids are directly toxic to bees and bumblebees, many other compounds used as herbicides and fungicides are also harmful to these insects. Obviously herbicides get rid of weeds, but weeds or wild flowers are a food source for these pollinators. Pesticides can have what are termed ‘sub-lethal effects’, so that the learning ability of the insects is reduced. Bees and bumblebees can learn which flowers are best as food sources, they can navigate to and from their nests / hives through open countryside. Also these compounds can affect their resistance to disease, and their fertility / reproduction. It is a concern that that bees’ honey stores may contain a cocktail of several pesticides that the bees have encountered during their foraging. In collecting pollen and nectar, a single bee may visit / pollinate four thousands flowers in a day. Not only are many thousands of wild flowers species dependent on bees for pollination but some three quarters of our food crops also need bees and other insects. Without them, the range and availability fo fruit and vegetables in our supermarkets would be substantially reduced. Whilst going organic and reducing reliance on the many forms of pesticide agriculturally is great help to pollinators, there is also good news in that small growers and even domestic gardeners can have a positive impact on the numbers of bees and others pollinators, such as : Planting a range bee-friendly plants in their gardens Creating a wild flower area in the garden or Allowing the lawn to grow up to form a small meadow like area Reducing the use of all pesticides - insecticides, herbicides, fungicides etc.
Woodland plants, on the move?
As a result of climate change, the physical characteristics of many ecosystems are changing. These changes may be in terms of humidity, temperature, soil moisture etc. As a result, plants and animals may no longer be suited to the new conditions, to survive they need to 'move on'. For a species to stay in its ‘comfort zone’, it may need to move ‘northwards’ or ‘upwards’ as climate change continues. Animals can walk or fly to new locations, even crossing inhospitable areas as long as the journey is brief. However, plants have a problem; they can only move by their seeds being dispersed, by wind, water or animals (including humans), though occasionally by underground stems or rhizomes. Not only that but the availability of suitable habitats to 'migrate to' is limited by the expansion of urbanisation and agriculture. Forests, woodlands and meadows have been reduced to a patchwork of islands, separated by roads, housing, vast monocultures of oil seed rape etc. Connections between natural areas are referred to as wildlife or biological corridors. These 'patches' of natural features enable wildlife to disperse / migrate, acting as 'stepping stones'. In a countryside that is becoming increasingly fragmented (across the UK and Europe) the role of wildlife corridors assumes greater importance. Read more...
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...
“tropical nights’ and greening our cities
Much of England experienced a series of ‘tropical nights’ last summer, when night time temperatures were 20oC or above. These tropical nights were associated with the heat wave that affected most of south east England. Central London experienced its longest stretch of extreme daytime temperatures since the 1960’s - temperatures of 30+oC were recorded on six consecutive days. A number of experts have said that such heatwaves and associated tropical nights are likely to become more common as a consequence of climate change. We were not alone in experiencing high temperatures by day and night, much of western Europe sweltered in the heat this August. The problem was most marked in urban areas and large cities. Some three-quarters of the population of Europe now live in urban areas. Extreme heat affects our health causing general discomfort, malaise, respiratory problems, headaches, heat stroke, heat cramps and heat-related mortality. Read more...
Woodland and hedgerow plants – the primrose.
Primroses were said to be the favourite flower of Benjamin Disraeli, indeed he wrote of them that he liked primroses so much better for their being wild “they seem an offering from the fauns and dryads of the woods”. On his death, Queen Victoria sent a wreath of primroses to his funeral with a note ‘his favourite flower’ (though it is not clear whether this referenced Disraeli or her late husband - Albert). Primroses are generally regarded as the harbingers of Spring, indeed the name Primrose comes from the latin for first rose - Prima Rosa. In different parts of the country, the primrose sometimes has other names such ‘Easter Rose’, ‘Lent Rose’ and ‘Early Rose’. Its scientific name is Primula vulgaris. Read more...
Woodlands web updates (2)
Holly and ivy have seasonal connotations, and due to climate change they are probably looking quite lush and vigorous at present. Studies have shown that in recent times, holly has spread further north in Europe than ever before - ‘pushing forward’ by some eighty miles since the 1960’s. Ivy too is on the move, growing vigourously. However with both plants, their growth can come as a threat to other woodland species, smothering some (Ivy can grow to great heights using its tiny adventitious roots) or when growing horizontally it can affect the herb layer. https://www.theguardian.com/science/2020/dec/16/plantwatch-holly-ivy-and-how-warmer-weather-boosts-christmas-plants Read more...