The UK is home to a single native species of crayfish – the white-clawed crayfish Austropotamobius pallipes. This attractive freshwater crustacean has a bronze-coloured body and white-undersides to its claws, for which it is named. They require clean freshwater habitats such as streams, rivers and lakes where they can rest under stones and rocks during the day and then spend the night foraging for food. Their diet is omnivorous and they feed on a range of foods including plants, carrion and invertebrates. They will also eat other white-clawed crayfish when the opportunity arises!
Threats to native UK crayfish
The white-clawed crayfish was once widespread and common throughout England and Wales, but since the 1970s populations have declined by 50–80%. Without intervention it is expected that they will become extinct over the next 20 years. Their decline is in large part due to the introduction of the North American signal crayfish which outcompetes the native crayfish for food and habitat. The signal crayfish also carries ‘crayfish plague’, a fungal disease that the white-clawed crayfish has no natural resistance to. Declining water quality and loss of suitable freshwater habitats have also contributed to their decline.
How are crayfish protected in the UK?
White-clawed crayfish are fully protected under the Wildlife and Countryside Act 1981 and The Conservation of Habitats and Species Regulations (2017). As a result, it is an offence to kill, injure or disturb them and their habitat cannot be destroyed or damaged. Any development which will, or is likely to, impact white-clawed crayfish and their habitat will only be allowed if it provides a net benefit to the crayfish through a combination of mitigation, compensation and enhancement strategies. This may involve habitat restoration projects or the modification of existing freshwater areas to make them more suitable for crayfish to survive and thrive.
When and how are crayfish surveyed?
Crayfish surveys are required if a development is being planned in an area that currently supports, or has the potential to support, white-clawed crayfish. They can be surveyed using a variety of methods including relatively new eDNA technology, which analyses water samples to detect the presence of DNA specific to the white-clawed crayfish. eDNA studies, however, cannot provide information on population size and so follow-up surveys are usually required should eDNA be detected. Most commonly crayfish are surveyed by manually searching likely refuges. If this isn’t possible due to access issues or water depth then crayfish traps can be deployed. These traps are of the live-catch variety – trapped individuals are returned to the water unharmed once they have been recorded.
What else is being done to conserve the white-clawed crayfish?
As well as being afforded a high level of protection in UK legislation, there are a number of conservation projects which aim to conserve or bolster existing populations of white-clawed crayfish. As part of the South West Crayfish Project, Bristol Zoo are breeding white-clawed crayfish in captivity which can be used to boost existing populations or establish new ones. They are also valuable in educating zoo visitors about their plight.
Control of introduced crayfish is also being carried out in certain areas through trapping or the use of biocides. Similarly, the control of plague and other crayfish diseases is of paramount importance. All waterway users should be aware of how easily plague spores are carried between sites and make all reasonable efforts to stop it spreading via their clothes and equipment. Download the Crayfish in Crisis information sheet for more information.
Recommended reading and equipment
Crayfish Conservation Manual
Full of guidance and practical advice, this large, full-colour manual is the first conservation handbook for England’s crayfish. This manual provides best practice advice and guidance in one easy-to-follow publication, with references, case studies and examples.
Management of Freshwater Biodiversity: Crayfish as Bioindicators
Integrating research into freshwater biodiversity and the role of keystone species, this fascinating book presents freshwater crayfish as representatives of human-exacerbated threats to biodiversity and conservation.
Trappy Funnel Crayfish Trap
This robust all-plastic crayfish trap is very easy to handle and quick to set and re-bait.
Aluminium Crayfish Refuge Trap
This simple refuge trap is safe for use where water voles and otters are present.
Snowbee Granite PVC Chest Waders
Snowbee Granite waders are manufactured from a heavy-duty, reinforced laminate PVC which is extremely tough and hard-wearing while also being soft and flexible for ease of movement.
The Mediterranean ecosystem is suffering the equivalent of a marine wildfire as temperatures in the area are more than 6°C warmer than normal. It is feared that the area is being permanently altered by global heating, with cooler deep water no longer rising to the surface. One study found that these marine heatwaves have already destroyed almost 90% of coral populations around parts of the Mediterranean. This decline has knock-on impacts on biodiversity within the marine ecosystems of the area.
A new project is looking at the genetic differences between bee species. ‘Beenome100’ will look to answer questions on which genetic differences make some species more vulnerable to climate change or more susceptible to different pesticides. By creating a digital repository of the complete set of genes present in 100 US bee species, scientists can link specific genes to bee functions.
Between 1986 and 2020, invasive herpetofauna cost the world $17 billion, $16.3 billion of which were associated mainly with just two species, the brown tree snake (Boiga irregularis) and the American bullfrog (Lithobates catesbeianus). This cost mainly comes from ruined farm crops and triggered power outages. The study’s researchers are hoping that their findings will encourage investment in preventing the spread of invasive species in the future.
UK wild salmon stocks are reaching a crisis point, with the lowest number on record in England. A government report urges action to remove barriers in waterways and improve water quality. 42 rivers in England are considered ‘salmon rivers’ as they are traditional breeding grounds for the fish. Of these, 37 have been classified as at risk or probably at risk. Warming sea temperatures due to climate change are being blamed, along with poor water quality in rivers and estuaries, with every waterway in England failing pollution tests in 2020. The main sources of pollution are thought to be sewage outflows and agricultural runoff.
Water voles have been reintroduced to the River Beane in Hertfordshire after being locally extinct for more than 20 years. Threatened by habitat loss and predation by the invasive American mink, the species has seen a 90% drop in population over the last five decades. Herts and Middlesex Wildlife Trust, in partnership with the Woodhall Estate and with the support of the River Beane Restoration Association, reintroduced 138 water voles to the river near Watton-at-Stone. Herts and Middlesex Wildlife Trust aim to reintroduce water voles to all Hertfordshire rivers by 2030, through these reintroduction programmes and by improving habitats.
A new Antarctic study has shown that the levels of ‘forever chemicals’ that are reaching this remote continent have been increasing. These chemicals include perfluorocarboxylic acid (PFCAs) and are termed forever chemicals as they do not break down naturally in the environment. They’re used in a variety of ways, such as in non-stick coating for pans and as water-repellents for clothing. The ice cores taken provide a record between 1957 and 2017 and show evidence that levels of these chemicals in Antarctic snow have increased over the last few decades, particularly between 2000 and 2017. There is ongoing research, however, into the clean-up of these forever chemicals, including a new study into bioremediation using a plant-derived material to absorb PFAs, disposing of them by allowing microbial fungi to eat them.
A new study has found that over 60% of global forest area has been lost. Using a global land use dataset, the team of researchers found that global forest area declined by 81.7 million hectares (ha) between 1960 and 2019. Gross forest loss was 437.3 million ha, outweighing gross forest gain during this time, which was 355.6 million ha. The loss of forests, both in the net area and through replacement by new growth/plantations, has a significant impact on the integrity of forest ecosystems, reducing their ability to sustain biodiversity.
In the lead up to the 26th UN Climate Change Conference of the Parties (COP26) in November of last year, and in the months that have followed, we have been writing a series of articles looking at some of the toughest global climate crisis challenges that we are currently facing. This blog looks at the causes of ocean warming and its impacts on marine ecosystems.
What causes ocean warming?
The ocean acts as a heat sink, absorbing large amounts of heat from our atmosphere and storing it over long periods; the ocean has a central role in stabilising our climate system. This heat is moved and mixed by tides, currents and wave action, allowing the ocean to soak up large amounts of heat without significant increases in temperature. This is changing, however, due to increasing concentrations of atmospheric greenhouse gases. IPCC data published in 2013 suggested that the ocean has absorbed over 90% of the excess heat generated by greenhouse gas emissions since the 1970s. This is resulting in increased ocean temperatures, with the greatest warming occurring in the southern hemisphere and in the upper 75m of the oceans surface. Average global ocean surface temperatures increased by 0.11°C per decade from 1971 to 2010. This heat sink process has helped limit the rise of global average temperatures but it has serious environmental consequences.
What are the impacts of ocean warming?
Ocean warming has a wide range of impacts on ocean chemistry, habitats, ecosystems and biodiversity, the severity and type of which can vary between habitats depending on their resilience and present biodiversity levels. Combined with other stressors such as pollution, acidification and increased nutrient input, ocean warming can increase the vulnerability of habitats and marine life to other threats such as parasites and disease outbreaks.
Water temperature is a significant environmental stressor, particularly in shallow or nearshore habitats, as they often act as nursery areas for many species. If water temperatures within nursery habitats rise above tolerable levels, they will no longer be suitable, impacting the survivorship, growth and recruitment of the species that use them.
Oxygen solubility varies depending on the temperature of the water; warmer ocean water holds less oxygen compared to colder water. Warmer water is also less dense, and rising ocean temperatures leads to increasing ocean stratification, where water is separated into layers. This can act like a barrier and prevents the mixing of water, slowing down ocean circulation and reducing the amount of oxygen reaching deeper waters. It is thought that dissolved oxygen levels have fallen by 2% since the 1950s due to the combined threats of ocean warming and excessive algae growth caused by anthropogenic nutrient input. Areas of low oxygen concentrations have expanded worldwide, with hundreds of new sites reported to be affected and anoxic ocean waters quadrupling in volume since the 1960s.
Ocean deoxygenation has serious consequences for marine ecosystems and biodiversity, as oxygen is necessary to sustain life for almost all organisms in the ocean. Deoxygenation could lead to a decline in species numbers, diversity and individual growth, resulting in major ramifications throughout the food chain. In ecosystems already vulnerable due to other pressures such as overfishing, deoxygenation could lead to extinctions and even deadzones. Hundreds of millions of people rely on the oceans as a source of food and livelihood; they could be severely affected by a reduction or collapse in fish stocks.
Warmer waters also increase the oxygen requirement of fish, exacerbating the effects of deoxygenation. There will likely be a shift in the structure of marine ecosystems as more hypoxia-tolerant species, such as jellyfish, will be favoured over less tolerant species, such as large fish and marine mammals.
Corals are marine invertebrates that often have a hard calcium carbonate skeleton. They live in a mutualistic symbiotic relationship with photosynthetic unicellular dinoflagellates called zooxanthellae (endosymbionts), which live in their tissues. They rely on these endosymbionts for up to 95% of their energy requirements. Under certain physiological stresses, such as increasing water temperatures, these endosymbionts can be expelled and the corals turn white without the pigment from the zooxanthellae – this phenomenon is known as ‘coral bleaching’. If the stress continues over an extended period and the coral is not recolonised, the coral will eventually die. Increasing ocean temperatures over the last few decades have resulted in large-scale loss of coral across the world. This has led to degraded coral reef habitats, impacting the ecosystem and species that rely on them. Coral reefs provide food, shelter and spawning grounds for thousands of marine species, therefore the degradation of coral reefs has wide-reaching consequences.
Habitat loss and range shifting
All species have a thermal tolerance range. Some more generalist species are able to tolerate a broader range, but specialist species occupy a much narrower thermal niche and are therefore more vulnerable to temperature change. Temperature changes can trigger a knock-on effect on ecosystem structures as species migrate into more suitable habitats. The general trends in these shifts are a movement to higher latitudes and deeper locations.
Many factors affect a species’ capacity to adapt to rising temperatures, including their dispersal ability, thermal tolerances, habitat or resource needs and the community composition of the new potential habitat. If the new area has high levels of pressure from competition, predation or lack of resources, or the species’ dispersal ability is limited (e.g. the species is sessile), successful establishment is unlikely.
Changes in community structure can negatively impact biodiversity, as the loss of whole populations from initial habitats can trigger a cascade of consequences on predator and prey populations, potentially altering entire ecosystems. These range shifts can also impact the communities already present, as new species could lead to increased competition for resources or the arrival of a novel predator that prey species are not adapted to avoid. There will also likely be socio-economic impacts on local fisheries if species move away from traditional fishing grounds.
Range shifting has been recorded in zooplankton, where warm-water species are extending their ranges poleward at a rate of up to to more than 230km per decade. There has also been a corresponding decline in the abundance of cold-water species in these areas. Zooplankton play a key role in many food chains as they are an intermediary species, transporting energy from the primary producers (phytoplankton) they consume to their predators, such as fish and decapods. Therefore, these changes in zooplankton community composition impact whole marine food webs, especially as warm-water species are generally smaller and less energy-rich.
Temperature-dependent sex determination
Some marine species exhibit environmental sex determination, where certain environmental factors can influence the sex of offspring during embryonic or early juvenile development. With increasing ocean temperatures, the proportion of males to females being born could be altered in certain species, leading to biased sex ratios. This can affect reproduction, genetic diversity and potentially population numbers.
Many fisheries are female-dependant, as female fish tend to grow larger, therefore are more likely to grow to harvestable sizes and can produce a larger yield. Southern flounder (Paralichthys lethostigma) exhibits sex reversal to males during early juvenile development at both 18°C and 28°C, with the optimal temperature for female development being 23°C. Southern habitats consistently have higher temperatures of over 27°C, therefore producing more male-biased sex ratios, potentially impacting the viability of fisheries operating out of these locations.
Warming ocean temperatures are also thought to be impacting breeding patterns, with many species reproducing earlier. This could lead to an uncoupling of certain predator and prey interactions if migrating predators arrive too late to feed during spawning events. Some species have been found to breed for a shorter duration, such as black sea bass (Centropristis striata) whose spawning season is starting later and ending earlier in the northern parts of their range. This suggests that there may be lower reproduction and recruitment in newly occupied ranges, demonstrating the potential future impact of warming ocean waters on species experiencing poleward-driven range shifts. Migration patterns have also been noted to be affected, with similar potential results.
Ocean warming also reduces the amount of sea ice. The implications of this, such as sea-level rise, coastal flooding and erosion, will be covered in more depth in a future blog post.
What can be done?
As the main driver for increasing ocean temperatures is the increase in atmospheric greenhouse gases, particularly carbon dioxide, the solution is to reduce our greenhouse gas emissions. Beyond this, we need to protect and restore our marine and coastal ecosystems and manage the other stressors that are exacerbating the impacts of ocean warming. By creating protected areas and restoring degraded habitats, we can create refuges for species and improve biodiversity, which has been shown to increase ecosystem resilience against the impacts of climate change.
By working with fisheries, governments could introduce further policies that work towards sustainability, such as by improving quota limits and reducing by-catch. Many governments and fisheries are already working towards this, but scientific research and accurate data are needed to ensure that population estimates are accurate to prevent overfishing. Steps like these will help to reduce the pressures we place on the marine realm, allowing ecosystems to be more resilient to the effects of ocean warming.
Scientific research into monitoring ocean warming is also important. Up-to-date and accurate measurements, with local and global monitoring of the rates, trends and effects can help policymakers make rapid and correct decisions to mitigate the worst impacts. Many of the policies signed at COP26 may make a positive difference, as reducing deforestation and methane emissions and adopting policies to reach net zero by 2050 will help to limit ocean warming. However, more can and should be done.
Oceans absorb atmospheric heat, the amount of which has increased due to high greenhouse gas emissions. The greatest warming occurs in the southern hemisphere and the upper 75m.
Ocean warming has a variety of impacts including deoxygenation, habitat loss, range shifting, coral bleaching and changes to breeding patterns. These various impacts can all have negative effects on marine biodiversity and human livelihoods.
As the main driver for marine warming is increased greenhouse gas emissions, the main solution is cutting these emissions. Other solutions include protecting and restoring marine habitats, reducing pressures from other threats such as overfishing and increasing the accuracy and use of scientific research.
This book discusses the modifications in marine ecosystems related to global climate changes, including shifts in temperature, circulation, stratification, nutrient input, oxygen concentration and ocean acidification, all of which have significant biological effects.
Charles Clover chronicles how determined individuals are proving that the crisis in our oceans can be reversed, with benefits for both local communities and entire ecosystems. Essential and revelatory, Rewilding the Sea propels us to rethink our relationship with nature and reveals that saving our oceans is easier than we think.
This authoritative and accessible textbook advances a framework based on interactions among four major features of marine ecosystems – geomorphology, the abiotic environment, biodiversity, and biogeochemistry – and shows how life is a driver of environmental conditions and dynamics.
This offers a short, self-contained introduction to this subject, beginning by briefly describing the world’s climate system and ocean circulation and going on to explain the important ways that the oceans influence climate. Topics covered include the oceans’ effects on the seasons, heat transport between equator and pole, climate variability, and global warming.
Wally Broecker is one of the world’s leading authorities on abrupt global climate change. In The Great OceanConveyor, he introduces readers to the science of abrupt climate change while providing a vivid, firsthand account of the field’s history and development. This book opens a tantalizing window into how Earth science is practised.
We have recently received the sad news of the passing of James Lovelock, an environmentalist, chemist, futurist and the creator of the Gaia hypothesis.
Born in 1919, he attended the University of Manchester at age 21 and graduated with a PhD from the London School of Hygiene and Tropical Medicine in 1948, becoming an independent scientist in 1961. He had since been awarded honorary degrees from several institutions, including the University of Exeter, Stockholm University and the University of Colorado Boulder. His career was varied, from travelling aboard the research vessel RRS Shackleton to working on developing scientific instruments for NASA, and even performing cryopreservation experiments.
Lovelock was the first person to detect Chlorofluorocarbons (CFCs) in the atmosphere after developing an electron capture detector in the late 1960s. CFCs are nontoxic chemicals used in the manufacturing of products such as aerosol sprays, and are used as solvents and refrigerants. Their role in the depletion of the ozone layer led to their inclusion in the Montreal Protocol, which worked to phase out several substances to protect the ozone layer. During his time aboard the RRS Shackleton, Lovelock measured the concentration of CFC-11 from the northern hemisphere to the Antarctic. These experiments provided the first useful data on the widespread presence of CFCs in the atmosphere, though the damage these cause was not discovered until the 1970s, by Sherwood Rowland and Mario Molina.
James Lovelock was also known for his Gaia hypothesis. This hypothesis, first created in the 1960s, proposed that the complex interacting system of the Earth’s biotic and abiotic parts could be considered as a single organism. Drawing from research by Alfred C. Redfield and G. Evelyn Hutchinson, Lovelock formulated that living organisms interact with the non-living environment to form a synergistic and self-regulating complex system, by co-evolving with their environment. He suggested that the whole system, including the biosphere, atmosphere, hydrosphere and pedosphere, seeks an environment optimal for life. This evolution is facilitated through a cybernetic feedback system that is unconsciously operated by the biota, leading to a final ‘state’ of full homeostasis.
While the Gaia hypothesis is generally accepted by many in the environmentalist community, there has been some criticism, particularly from the scientific community. Lovelock later made revisions to the hypothesis to clarify that there was no conscious purpose within this self-regulating system and to bring the hypothesis into alignment with ideas from other fields, such as systems ecology. This had reduced criticism, but there still remains scepticism from the scientific community.
Lovelock wrote more than 200 scientific papers as well as a number of books on a variety of topics within chemistry, environmentalism, geophysiology, climate change and more. Lovelock’s work has been recognised a number of times, receiving awards such as the Tswett Medal in 1975, the Dr A. H. Heineken Prize for Environmental Sciences in 1990 and the Royal Geographical Society Discovery Lifetime Award in 2001. He was also appointed a member of the Commander of the Order of the Britsh Empire for services to the study of Science and the Atmosphere in 1990 and a member of the Order of the Companions of Honour for services to Global Environmental Science in 2003. In 2006, he was awarded the Wollaston Medal, an achievement also received by Charles Darwin.
Fen, Bog & Swamp, from Pulitzer Prize winning author Annie Proulx, is a wide ranging book that meanders through the subject of wetlands on a journey which encompasses history, biology, language, culture, art and literature. Written in a passionate and lyrical voice, the book is not only a thorough exploration of these ecosystems, but also a war cry in their defence, although one that at times feels dampened by the assumption of inevitable defeat. This is echoed in a statement in which she describes her intentions behind the writings and research: “Before the last wetlands disappear I wanted to know more about this world we are losing. What was a world of fens, bogs and swamps and what meaning did these peatlands have…”.
The book is arranged into four loose parts: an introduction of “discursive thoughts on wetlands”, followed by individual chapters covering fens, bogs and swamps. Beginning the text with a description of a fond yet distant memory of walking through a swamp with her mother as a child in 1930s Connecticut, which she describes as her “first thrill of entering terra incognita”, Proulx goes on to bemoan the disinterest of modern humans in “seeing slow and subtle change” and the “slow metamorphoses of the natural world”. In our fast-paced lives in which speed and efficiency are hailed as the twin gods of progress, there are few who can, or desire to, repetitively observe the same flowers, trees or waters, week after week, season after season, or to appreciate the myriad yet microscopic ways in which they change. For this reason, evidence for a warming climate and its impending crisis have been easy to ignore until the impacts are so visible that they can no longer be shuffled under the carpet.
As a reader based in Britain, I found the section on fens to be of particular interest, despite the fact that their story is ultimately one of destruction and decline. These days it is hard to imagine a Britain in which 6% of the land was wetland, all of which provided a “source of wealth that could hardly be surpassed by any other natural environment”. Now, in modern Britain, less than 1% of the original fenlands remain: a mere fragment of this once great and diverse habitat.
Proulx’ wonderful descriptions of the people who lived in the fens and how an intimate knowledge of its creeks, rivers and mudflats allowed them to thrive in this challenging landscape are particularly pleasing. Using descriptions of artwork and quotations from literature (such as the Moorlandschaften photographs of Wolfgang Bartels and Gertrude Jekyll’s wonderful vignette on the use of rush-lights) Proulx paints a vivid picture, not only of the historical landscape, but also of the lives of the people inhabiting them.
In fact, these diversions into the lives of the people who have impacted and been impacted by wetlands occur frequently throughout the text, and are used to great effect to provide an insight into changing minds and cultures. From stories of the 16th century Spanish explorers to those of naturalist Henry Thoreau and botanist William Bartram, the book is littered with potted biographies that tell the stories of the people who were fascinated by these landscapes, as well as the darker sides of exploitation and greed.
Through the telling of these stories, it becomes apparent that fens, bogs and swamps have long been derided by humans. This is exemplified by the pre-15th century British fen dwellers who were “literally and metaphorically looked down on” by the upland people in a manner that was reflected in their view of the fenlands themselves. Also mirrored in the attitude of European settlers in the US who despised the swamps for slowing down movement and progress and limiting productive agriculture, wetlands throughout the world have consistently been viewed as ‘waste, unproductive’ areas, in need of ‘improvement’.
Time and time again we have blundered around in the name of progress, attempting to drain, farm, reforest and develop these regions with little knowledge of how to maintain them afterwards, or even whether this is possible. Indeed, as is now apparent in areas such as New Orleans and Chicago, where the water is slowly taking back the land, the fight against nature is likely to be a long drawn-out game that we are unable to win.
As you might expect from someone whose life has been concerned with words, Proulx pays a lot of attention to the language surrounding fens, bogs and swamps. Highlighting such examples as the equally pleasing Pocosin (swamp) or Muskeg (bog), she also draws parallels between the loss of these habitats and the loss of the language that we can usefully use to describe them. In a manner that has also been highlighted by writers such as Robert MacFarlane in Landmarks and The Lost Words, it seems that this is a two way street: as we lose the habitats, we also chip away at the list of nouns and adjectives that are used to describe them; but equally, with the loss of this nuanced language, we also begin a process of forgetting and dismissing the landscapes themselves.
I came away from reading this book with a new appreciation of fens, bogs and swamps, but also saddened by the fact that, as Oliver Rackham stated, the long history of wetlands is ultimately a story of their destruction. As Proulx simply states in her final lines, in an echo of those words from Norman Maclean’s A River Runs Through It, perhaps the time is coming when we will all be “haunted by waters”.
Fen, Bog & Swamp: A Short History of Peatland Destruction and Its Role in the Climate Crisis is available for pre-order from NHBS and is due for publication in September 2022.
Seeing dragonflies swoop over water is a quintessential sign that summer is upon us. When in flight their movements are mesmerising – using their two sets of wings either in synchrony or beating separately, they are able to fly in any direction they choose, altering their speed and movement instantly in mid-flight to create a dance that is unlike any other organism. But while the flying adults are frequently seen during the warmer months, many of us know very little about their life during the rest of the year.
In this article we will take a look at the dragonfly life cycle, explore how climate change and other threats are affecting dragonfly populations globally, and offer some tips on how to attract dragonflies to your garden.
Dragonfly life history
Dragonflies belong to the order Odonata within the sub-order Anisoptera (meaning ‘unequal-winged’). This order is also home to the closely-related damselflies (sub-order Zygoptera). Although at first glance dragonflies and damselflies appear similar, dragonflies are usually larger and bulkier with significantly larger eyes when compared to the slightly built and rather delicate damsels. When at rest dragonflies hold their wings open whereas damsels keep theirs closed, next to the body.
There are three distinct phases in the dragonfly life cycle: egg, nymph (larva) and adult.
Dragonflies breed in or on water bodies such as marshes, swamps, ponds, pools and rivers; after mating the female will lay hundreds of eggs over the course of several days or months. Some species lay their eggs inside plant material, either on the surface of the water or submerged. Others encase their eggs in a jelly-like substance and deposit them directly into the water. Eggs usually hatch within a few weeks, although some remain in the water throughout the colder months and hatch the following spring.
The first larva that hatches from the egg is known as a prolarva, and this very quickly moults into the first proper larval stage. The larvae, or nymphs, then proceed to moult a further 5–14 times – typically taking place over 1–2 years, although it can be as long as five years in species such as the Golden-Ringed Dragonfly. Nymphs continue to live in the water and are voracious eaters, feeding on insect larvae, crustaceans, worms, snails, tadpoles and even small fish.
Unlike many other flying insects, such as butterflies and moths, the final moult of the dragonfly does not feature a pupal stage – known as incomplete metamorphosis. This moult takes place out of the water where the winged adult emerges from the nymph skin, leaving behind an exuvia, or skin cast. A period of time is then spent feeding away from the water before the adult dragonfly returns to breed and begin the cycle again. Life expectancy of the adult dragonfly is short – typically only 1–2 weeks, although some will live for up to 5–6 weeks.
Conservation and climate change
An IUCN update in December 2021 stated that the destruction of wetlands is driving a worldwide decline in dragonflies. Despite their high ecological value, marshes, swamps and boggy areas continue to be degraded by intensified agriculture and urbanisation and, along with longer periods of drought, this is vastly reducing the amount of habitat in which dragonflies and damselflies can survive.
Clean water is also paramount for dragonfly nymphs – so much so that their presence is regarded as an useful indicator of wetland health. Pollution of waterways and water bodies by pesticides and effluent are problematic and are compounding the issue of habitat loss.
In their favour is the fact that dragonflies are highly mobile and appear to colonise new habitats relatively rapidly. With global temperatures on the rise, we are already seeing species shift to higher latitudes and altitudes. Even in the UK, Mediterranean migrants are being recorded with increasing frequency.
Which dragonflies are you most likely to see?
There are just under 30 species of dragonfly living in the UK. Identification of these is primarily achieved using the patterns and colouration of the thorax and abdomen, although a few similar species require the finer details, such as leg colour, to be examined.
Or why not check out this interactive map from the British Dragonfly Society where you can search for good places to look for dragonflies near you. You can also filter the results by species if you’re looking for something specific.
How to attract dragonflies to your garden
Water is an integral part of the dragonfly life cycle, so having a pond in your garden is by far the best way to attract them. If you only have a small outdoor space then sinking a bucket or trough into the ground is a low-cost and space-efficient solution. A larger pond with both floating and emergent vegetation, however, will provide dragonflies with somewhere to lay their eggs and for the nymphs to live once they have hatched. It is important to have some vegetation which extends out of the pond as this will allow nymphs to leave the water when they are ready to undergo the final moult into their adult, winged form. Ponds with carnivorous fish or those used by waterfowl will be less useful as these will both prey on the dragonfly larvae.
Having a variety of flowers and herbs growing nearby will help to attract other insects which the dragonflies will feed on. Providing some canes or small stakes will also give them a place to perch – this is particularly important in the morning when dragonflies need to spend time basking in the sun before their wing muscles are warm enough for flight.
• Dragonflies see the world in colour and can detect ultraviolet as well as blue, green and red.
• Dragonflies have been around for 300 million years. Their ancestors were some of the largest insects ever to have existed – some had wingspans of up to 80cm!
• Dragonflies are true acrobats and can fly both upside down and backwards.
• Although they can live for up to five or six years, dragonflies only spend a tiny portion of this time – between a week and two months – as the colourful flying adults that we recognise. The majority of their lives are spent in the water as nymphs (larvae).
Further reading and equipment
Field Guide to the Dragonflies of Britain and Europe
A superb identification guide with identification texts and distribution maps as well as an introduction to larvae identification. Each species is lavishly illustrated with artworks of males, females and variations, as well as close-ups of important identifying characters.
Britain’s Dragonflies: A Field Guide to the Damselflies and Dragonflies of Great Britain and Ireland
Written by two of Britain’s foremost dragonfly experts, this excellent guide is focused on the identification of both adults and larvae. It features hundreds of stunning images and identification charts covering all 57 resident, migrant and former breeding species, and six potential vagrants.
Guide to Dragonflies and Damselflies of Britain
This handy and affordable fold-out guide from the Field Studies Council features 28 dragonfly and 16 damselfly species and is a useful aid to identifying them in the field, often while in flight. It is a perfect size to pack into a bag while out and about and is a great choice for beginners.
The European Parliament has voted to ban ‘fly shooting’ fishing in a part of the Channel. This technique, also known as demersal seigning, involves towing weighted ropes along the seabed at either end of a net, which then encircles and captures entire shoals of fish. Fly shooter vessels catch up to 11 times more fish than inshore fishing vessels and have a devastating effect on the marine ecosystem, biodiversity and local fishers. This decision is seen as a victory for small-scale fishers but it will also help reduce the damage caused to the seabed and marine ecosystems in the Channel.
The Environment Agency (EA) is calling for water company bosses to be jailed for serious pollution. Shocking levels of pollution occurred in the last year, with 62 serious incidents of pollution in 2021. The EA has stated that chief executives and board members of companies responsible for the most serious incidents should be jailed and that courts should impose much higher fines. Only three water companies received the highest rating of four stars for their pollution performance. The rating takes into account the number and severity of pollution incidents, as well as self-reporting and the use and disposal methods of sewage sludge. Two companies, Southern Water and South West Water, were given the lowest rating of one star.
3D printed reefs are being used to restore marine biodiversity. WWF Denmark and Ørsted have been testing how structures made of 70% sand and 30% pozzolanic cement (a combination of volcanic ash and portland cement) could be used to create new habitats for fish and other wildlife in the Kattegat strait between Denmark and Sweden. Twelve of these structures have been deployed between the wind turbines at Anholt Offshore Wind Farm, and it is hoped that they will help reverse the decline of cod stock in the Kattegat.
Bison have been released into the wild in the UK. Wild bison are ecosystem engineers and can help to restore biodiversity in woodlands through their natural behaviours, such as felling trees by rubbing against them and grazing. This is hoped to provide a nature-based solution to tackling the climate and biodiversity crisis. The releases are part of a five-year project led by Kent Wildlife Trust and the Wildwood Trust. The next steps include introducing Exmoor ponies, Iron Age pigs and Longhorn cattle.
Young Maori divers are hunting invasive crown-of-thorns starfish to save coral reefs. The species, also known as taramea, feed on coral reefs and, when there are too many individuals, can destroy reef habitats. Korero O Te `Orau, a local environmental organisation, has been training young Maori people in scuba diving to remove taramea from the reef and bury them inland. The recent outbreak of this species around the island of Rarotonga in the Cook Islands could jeopardize the survival of the surrounding coral reef if not tackled properly. More than 3,700 taramea have been collected so far.
Great white sharks might change their colour when hunting prey. Researchers conducted experiments off of South Africa using a specially designed colour board with white, grey and black panels. Each shark was photographed as it jumped out of the water at the panels, with the experiment being repeated throughout the day. One particular shark appeared to be both dark grey and a much lighter grey at different times. The results were verified using computer software to correct for variables such as weather, light levels and camera settings. While the research has not yet been validated and published in a scientific journal, experts are still excited about the results.
We are pleased to announce that we are now able to resume manufacturing the NHBS Harp Trap! We have had the time to be able to think about the design of the trap and tweak it to make it easier to use. At first glance, this compactly packed harp trap may look as though it would be tricky to set up, but rest assured that, with the use of two people, you’ll be able to easily assemble this trap, even in the dark. This blog provides a step-by-step guide to how to set up and disassemble the trap. If you are interested in finding out more general information about the NHBS Harp Trap, the only harp trap that is commercially produced in Europe, and its use, please check out the blog we wrote when we first launched the trap.
Please note that the NHBS Harp Trap is a made-to-order item so please contact us if you would like to purchase one and we will be happy to advise the current lead time.
The NHBS Harp Trap: Instructions
Please follow these instructions for correct assembly and disassembly. We recommend that this is carried out by two people.
1. Carefully remove the harp trap from its carry bag and sit it upright on the floor still wrapped up. Remove the legs and upright support poles from on top of the trap.
2. Insert the legs at either end of the frame (it is easiest to do this one end at a time). Hand tighten the top thumb screws (A). The lower thumb screws (b) are for extending the legs to make the trap higher or balanced if on uneven ground; the leg lengths can be adjusted as needed after the trap is assembled.
3. Undo the material ties at the bottom of the trap (C) to unroll the green catch bag flap so that it is laid out on the floor (D).
4. Fully open out the catch bag assembly arms to their full width (D).
5. Remove the upper carriage securing pin by loosening the upright support pole thumb screws (E). Where the upper carriage securing pins have been removed, insert upright support poles and allow them to rest on the ground. Ensure that the fixing points (thumb screws) on the upright support poles are facing each other.
6. Release the spring locking pins from both ends of the trap by pulling the leaver out and rotate it 90° to lock in open position (F).
7. Remove the thumb screw from the top of each upright support pole and slowly raise the top line carriage, keeping both ends level and watching closely to ensure that the lines do not become jammed. Once the carriage reaches the fixing point secure with upright support pole thumb screws.
8. Once you are confident that the top carriage is secure, slowly lift the upright support poles in unison again, and carefully watch the lines to ensure that none get caught. Keep raising until the lines become taut. Engage both spring locking pins in the bottom carrier (reverse of F), check the tension is even at both ends of the trap and when happy tighten the two thumb screws at the base of the upright support poles evenly at both ends to secure.
9. If required, peg out the guy ropes for extra stability.
1. If guy ropes have been used pull out the red pegs and store them carefully. Now wind up the guy ropes.
2. While holding on to the upright support poles (one person at each end), loosen the thumb screws at the base of the upright support poles, holding them in position and allow them to lower slightly. Disengage the spring locking pins on each end (as in F) and start to wind the lower line carrier. Keep lowering the upright support poles slowly and evenly while winding the line carrier until the upright support poles reach the floor.
Care must be taken to not allow the line to come free off the end of the line carrier as this may result in snagging of the lines and subsequent breakage – guiding the lines with your hand/arm while lowering is essential (H).
3. With the upright support poles resting on the ground, remove the top carriage securing thumb screws and allow the line carrier to lower, guiding the line with your hand/arm and winding as you go (H). Return the top line carrier thumb screws back to the storage points in the upright support poles.
4. Once the top carriage has been fully lowered, engage the spring locking pins, remove the upright support poles, and secure the top carriage back into storage position using the upper carriage securing pin and tighten the thumb screws to secure in place (reverse of E).
5. Fold the arms of the catch bag assembly inwards as far as they will go, wrap the bag around the trap and tie the bottom attached material straps to secure in place.
6. Undo the top thumb screws that are securing the legs and remove each leg. For safekeeping, ensure that the thumb screws are tightened once the legs have been removed.
7. Fully collapse each leg to its minimum length and tighten with thumb screws.
8. Place the upright support poles and legs back on top of the closed trap and secure them in place using the attached material ties at either end. Carefully place the trap and accessories bag back in the carry bag safely ready for next time.
Spares and accessories included:
4x Guy rope 5m
4x Red pegs
1x Roll of nylon string
1x Accessories bag
The NHBS Harp Trap is available on the NHBS website. The trap is available as a three-bank trap as standard, but please contact our Workshop Team to discuss your requirements if you would like a bespoke two or four-bank trap, or if you would like a trap that has the ability to be suspended from a support.
To view the full range of NHBS manufactured items, along with other ranges of survey equipment, visit www.nhbs.com. If you have any questions on the NHBS Harp Trap or would like some advice on the best survey equipment for you then please contact us via email at firstname.lastname@example.org or phone on 01803 865913.
Managing habitats for the benefit of wildlife can often contradict climate priorities. In the Summer 2022 issue of Conservation Land Management (CLM), Malcolm Ausden and Rob Field describe how different habitats and their maintenance impact the climate, and highlight the management practices that provide the greatest climate benefits. Here you can read a summary of the article.
Quantifying the impacts of habitat management on the climate
The influence of different habitats and their management on the climate can be measured by estimating the net flux of the most important greenhouse gases (GHGs): carbon dioxide, methane and nitrous oxide. The contribution of the latter two is usually expressed in terms of the amount of CO2 needed to produce the same level of warming (tonnes of CO2 equivalent; t CO2e), as determined by global warming potential (GWP) of the different gases. A positive GWP indicates a positive warming effect, whereas a negative GWP shows a cooling effect. GWP values are usually expressed in comparison to the warming potential of CO2 over 100 years.
The effects of conservation land management on GHG flux
In the full CLM article, the authors describe the GHG flux of the main types of habitats in Britain, and how this is affected by conservation management. The habitats included are listed below, starting with those that produce the greatest overall warming effect on the climate, and finishing with those that have a cooling effect.
Intensive arable on organic soil
Intensive grassland on organic soil
Eutrophic/mesotrophic open water
Lowland wet grassland on organic soil
Intensive arable on mineral soil (incl. emissions from farming operations)
Oligotrophic open water
Heather-dominated drained bog
Intensive arable on mineral soil (excl. emissions from farming operations)
Lowland and upland heathland
Unimproved low-input grassland (incl. LWG on mineral soil)
Improved grassland (excl. emissions from farming/livestock operations)
Conifer plantation on mineral soil (managed on a 55-year-rotation)
Dry broadleaved woodland (mean over first 100 years)
Dry broadleaved woodland (mean over first 30 years)
Intensive arable on organic soil (soils derived from peat) produces the biggest warming effect per unit area, as large quantities of CO2 are released via oxidation of dried-out peat that is repeatedly exposed during the cultivation process. The manufacture and use of nitrate fertilisers and the use of machinery also contributes to significant emissions of GHGs. At the other end of the spectrum is dry broadleaved woodland, particularly during the first 30 years after its establishment. The GHG flux of woodland fluctuates depending on its age, species composition, the density and growth rate of trees, and management. For unmanaged woodland, the net uptake of CO2 is low while trees are small, and planting of trees can even lead to a net release of CO2 as a result of soil disturbance. The rate of CO2 uptake increases during the main growth stage of the trees, slowing as they mature, although carbon does continue to accumulate in the soil.
Ways to benefit both the climate and wildlife
Conservation management can provide climate benefits either by reducing the amount of GHGs released into the atmosphere, or by actively removing them (i.e. carbon sequestration). For example, rewetting drained peatland reduces, and should eventually stop, the release of CO2 that occurs through the drying out and oxidation of peat. Although there is an initial release of methane after rewetting, accumulation of carbon in the peat will resume. The climate benefits per unit area of wet peatland are surprisingly low compared to some other types of habitat, but due to the large quantities of carbon stored within the vast expanse of peat in upland Britain, rewetting drained areas is an incredibly important measure to prevent the ongoing release of CO2, and will also provide a number of benefits for wildlife.
On organic soils used for arable, the greatest climate benefits per unit area come by creating wet woodland, as this prevents the oxidation of the peat and allows carbon to accumulate during tree growth. There are, however, limited opportunities to create new wet woodland on ex-arable organic soils and to keep them adequately saturated. The next best option is the creation of swamp/fen, which offers far greater climate benefits than agriculturally drained peat soils, even though the habitat itself has an overall GWP100 near to zero.
The authors look at multiple management approaches and describe the climate benefits of different types of habitat restoration and creation. All the methods listed below are beneficial for the climate, and are ordered here by the magnitude of their cooling effect, from the least to the greatest.
Creating swamp/fen on ex-arable on mineral soil
Rewetting drained bog
Creating lowland wet grassland on ex-arable on mineral soil
Creating intertidal habitat on ex-arable on mineral soil
Establishing broadleaved woodland on ex-arable on mineral soil
Creating lowland wet grassland on drained grassland on organic soil
Creating swamp/fen on drained grassland on organic soil
Creating lowland wet grassland on ex-arable on organic soil
Creating swamp/fen on ex-arable on organic soil
Creating wet woodland on ex-arable on organic soil
A large aspect of the management of semi-natural habitats involves cutting and clearing vegetation in order to maintain a particular vegetation structure and to slow or reverse succession. But this means that the amount of carbon accumulated in the soil and vegetation is reduced. In addition, the removal of vegetation is often carried out by using domestic livestock, which release large quantities of methane, by machinery, which is often powered by fossil fuel or biofuel and releases CO2, or by burning, which also releases CO2.
But there are changes that can be made to management that can help contribute to a habitat’s cooling effect. For example, the amount of vegetation that is removed from a site can be reduced to allow more carbon to be stored in the vegetation or soil. In some instances this can mean allowing a site, such as a swamp/fen, to develop into woodland or scrub. This can contradict conservation goals where maintaining an early successional habitat is the priority, but can be an option for sites that are currently poor for wildlife.
Another option is to change the method used to clear the vegetation. One way that this can be achieved is by swapping livestock for grazers that release less methane per quantity of vegetation removed. Ponies, for example, produce much lower levels of methane compared to cattle and sheep, although before changing the type of livestock it is important to understand that different livestock have different effects on vegetation structure and composition. In the full article, the authors explore this and other changes that site owners can make to increase the cooling effect of different habitats and their management.
It can be difficult for conservationists and land managers to know how to best manage a site in the interest of both nature conservation and the climate, and in many cases there are trade-offs between maximising the benefits for the two. But as the article demonstrates, there are restoration approaches that can be used that provide significant climate and conservation benefits, and it is helpful to consider and quantify the net flux of GHGs before implementing any changes to conservation management plans.
Other articles featured in the Summer 2022 issue include:
Saltmarsh restoration through flash re-creation
Measuring conservation success on farmland
Viewpoint: Dams without beavers: could beaver dam analogues yield benefits in the UK?
In this and every issue you can expect to see Briefing, keeping you up to date with the latest training courses, events and publications, and On the ground which provides helpful tips or updates on products relevant to land management. Other features that regularly appear in CLM include Viewpoint, a similar length to our main articles, but here authors can voice their own views on various conservation issues, and Review, which can include letters from readers or updates from our authors.
CLM is published four times a year in March, June, September and December, and is available by subscription only, delivered straight to your door. Subscriptions start from £22 per year. Previous back issues are also available to purchase individually (subject to availability).
If you are involved in a conservation project and think your experiences could be useful to other practitioners, we would love to hear from you. If you are interested in writing for CLM feel free to contact us – we will be happy to discuss your ideas with you.
For those of us living where there are four distinct seasons, summer is the period of long, warmer days where the skies, fields, lakes and mountains are alive with the busy activities of plants and animals at the peak of their growing year. Most of the animals that have hatched or been born earlier this year will be beginning to fend for themselves, while many plant species will be coming to the end of their flowering period and preparing to produce seed in an effort to ensure their survival and proliferation.
The combination of warmer weather and longer daylight hours makes this the perfect time to get out and about and experience the beauty and complexity of the natural world.
This is the second in our seasonal phenology series where you can explore a carefully chosen collection of ID blogs, books, equipment and events, all designed to help you make the most of a summer outside. Check out our spring blog and don’t forget to look out for our autumn blog in September.
What you might see:
• Hedgerows and verges are still home to lots of flowering plants, although the frothy drifts of cow parsley are now coming to an end. Honeysuckle can be seen blooming from June, providing a night-time food source for moths such as the Elephant Hawkmoth (Deilephila elpenor).
• Bee orchids (Ophrys apifera) will flower briefly in June and July on dry, chalk and limestone grasslands, while sea cliffs will be adorned with the delicate blush of sea thrift (Armeria maritima) from April to October.
• Auks, such as Razorbills (Alca torda), Guillemot (Uria aalge), Puffins (Fratercula arctica) and Fulmar (Fulmarus glacialis), come to their cliff nests in spring to lay their eggs. They can still be seen (and heard!) throughout the summer as they make frequent trips out to sea to catch food for their young. Further inland, summer visitors such as Redstart (Phoenicurus phoenicurus), Wood Warblers (Phylloscopus sibilatrix) and Pied Flycatchers (Ficedula hypoleuca) are wonderful to catch a glimpse of.
• June to August is an important time for ladybirds. During this period, mated females will lay their eggs which then hatch into larvae and form pupae through a series of four stages, or ‘instars’. Adult ladybirds emerge from the pupae in August.
• Wasps, bumblebees, honeybees and butterflies are all active in the summer and will feed as much as possible while the weather is fine. Small Tortoiseshell (Aglais urticae) and Red Admiral (Vanessa atalanta) butterflies can both be frequently seen around nettles where they like to lay their eggs.
• Frogs and toads spend their days keeping cool in damp and shady areas and are often found in overgrown areas of the garden during the summer. This year’s froglets and toadlets will remain in the water until late summer.
• The summer months are a great time to spot bats hunting for insects during the dusk and dawn hours. Female bats give birth to their young in June and within three weeks these juveniles will be learning to fly themselves. By August the youngsters will no longer need their mother’s milk and will be hunting for their own food.
Field Guide to the Moths of Great Britain and Ireland
This beautifully illustrated and comprehensive field guide shows moths in their natural resting postures. It also includes paintings of different forms, underwings and other details to help with identification.
Britain’s Reptiles and Amphibians: A Guide to the Reptiles and Amphibians of Great Britain, Ireland and the Channel Islands
This detailed guide to the reptiles and amphibians of Britain, Ireland and the Channel Isles is designed to help anyone identify a lizard, snake, turtle, tortoise, terrapin, frog, toad or newt with confidence.
The Wild Flower Key: How to Identify Wild Flowers, Trees and Shrubs in Britain and Ireland
This essential wild flower guide is packed with identification tips and high-quality illustrations, as well as innovative features designed to assist beginners. The text aims to be as useful as possible for those working in conservation and includes a compilation of the latest research on ancient woodland indicator plants.
NHBS Moth Trap
A lightweight and highly portable trap, tested and approved by Butterfly Conservation. This mains-powered trap runs a single 20W blacklight bulb (included) and comes supplied with a 4.5m power lead with UK plug.
Kite Ursus Binoculars
These affordable binoculars have been designed for everyday use and have a robust housing, great field of view and produce a bright, colour-balanced image.
Magenta Bat 5 Bat Detector
A handheld super-heterodyne bat detector with an illuminated easy-to-read LCD frequency display. This fantastic entry-level detector converts ultrasonic bat calls into a sound that is audible to humans, allowing you to listen to and identify the bats flying around you.