Seasonal Update (July 2021)

This year has been anything but normal weather-wise, with summer only showing itself in brief pulses so far. - Credit: Marc Baldwin

After a colder and wetter than average month, May ended on a high, with widespread dry and sunny weather and temperatures well above the seasonal average, peaking at 25.1C (77.2F) at Kin-Loc-Que on the Bank Holiday Monday. June started off in the same vein, with clear blue skies across all but the far east of England, where low cloud was persistently hugging the North Sea coast, and the far west of Ireland and Scotland, which saw some rain on Tuesday. Temperatures on 1st June peaked at 26.1C (79F) in Cardiff, but under that persistent North Sea cloud, parts of the east coast managed only 11C (52F). The mercury inched higher on the Wednesday, with temperatures hitting 28C (82F) in Chertsey, while a fragmented band of thunderstorms worked their way north and west during the day. Things remained dry for most of the UK for the rest of the week, bar some heavy and thundery showers in the southeast. The latter part of the week was also cooler, with temperatures widely in the high teens and low 20s Celsius (high 70s Fahrenheit).

The first weekend was one of two halves. The Saturday was broadly warm and sunny with clear blue skies, bar the far southeast, which saw some showers passing through. Sunday, by contrast, started out as a mostly cloudy affair, cooler and with some patchy mist and drizzle, before brightening up during the late afternoon.

The second week kicked off widely warm and sunny, albeit with a chilly breeze, before cloud and patchy light rain fed into the west, suppressing the sunshine and thus temperatures for Ireland, Wales and much of Scotland. This cloud was the leading edge of a weather system that brought more persistent, but still fragmented, rain into Ireland and western Scotland on Tuesday; eastern England remained dry and sunny. The remainder of the week was broadly the same east-west split, with more sunshine and warmth in the east. The west saw much more cloud with some patchy rain further north. The humidity also built as the week progressed, with overnight lows only dropping into the mid-teens Celsius (high 50s Fahrenheit) - Altnaharra in the Scottish Highlands, for example, had an overnight low of 17C (63F) on Tuesday night, which is about what they'd normally expect as daytime highs this time of year. The wind strengthened, courtesy of high pressure over south-west Europe and a deep low over Iceland, and things freshened up towards the end of the week as a weather front pushed south and east on Friday.

Altnaharra in the Scottish Highlands experienced a vast range of overnight lows last month, from -2C to 17C. - Credit: Tim Haynes (CC BY-NC-ND 2.0)

Dry, hot and sunny was the state of play across England and much of Ireland to start the second weekend thanks to high pressure building in from the Azores, with things cloudier but still dry in Scotland. The south-east saw temperatures in the high 20s Celsius (high 80s Fahrenheit), while Scotland tipped the Mercury at a somewhat cooler 21C (70F). The first half of the third week was generally the same - dry, warm and sunny across the board, bar the west of northern Ireland and Scotland, which saw some rain, and the north coast of Cornwall that was cloaked in low cloud and mist for most of the day.

Come Wednesday, the situation changed and heavy thundery showers moved up from the near continent and spread across most of England. The showers were patchy in nature on Wednesday night and Thursday, but much more concentrated and very heavy on Friday, the front working its way north through the day with all but the south-west of England and parts of western Wales escaping a deluge. Friday saw persistent, torrential rain for almost 24 hours, with some parts of eastern England seeing several weeks’ worth of rain over that period - parts of Kent saw just over a month's worth and across the UK as a whole the Met Office issued 39 flood alerts. Temperatures under the cloud were very disappointing, peaking at only 12C (54F).

The penultimate weekend was mostly cloudy and chilly (~14C/57F) along the east coast thanks to a keen north-easterly wind. A second, smaller weather system moved north bringing more showers overnight Saturday and into Sunday morning, but substantially fewer than we had seen on the Friday. The showers and chilly feel continued to the Summer Solstice on Monday, with a band of heavy and persistent rain sat across southern England all day, while the rest of the UK and Ireland remained predominantly dry. Monday night was unseasonably cold in the north, falling widely to 0C (32F) in Scotland, down to -2C (28F) in Altnaharra, while London started Tuesday at 12C. The rain pushed off south into Europe overnight on Monday, leaving Tuesday as a predominantly dry day for all except the Channel Islands, which saw rain for most of the day, before another weather system pushed into the west of Ireland and Scotland towards the end of the day, edging a little further south and east into England on Tuesday night.

Wednesday was cloudy and drizzly in the north and west, and mostly dry and sunny in the south and east, with temperatures ranging from 13C to 21C (55-70F). Thursday saw the weather system push south and east, with all but the far east of England and northwest of Scotland remaining dry all day. The northern edge of the front moved back into Scotland early on Friday while the southern quadrant brought patchy rain to the south coast. Circling down south, the front brought quite persistent rain to Wales and the Midlands, with the north-easterly breeze behind it dropping temperatures widely into the mid-teens Celsius.

The final weekend was again one of two halves. Saturday was warm and dry pretty much across the board, with temperatures into the mid-20s Celsius. Sunday, by contrast, started cloudy before brightening up later in the morning. Along the south coast, a large low-pressure system pushed in from France, bringing heavy showers and some thunder and prompting the Met Office to issue a yellow warning for rain. The system tracked slowly north, ending up with its northern front in a diagonal line roughly from southern Wales in the west to Hull in the north come the early hours of Monday. The remainder of the UK and Ireland stayed dry, with some patchy cloud. The rain remained in England throughout Monday, particularly in the east, fragmenting into patchy thundery showers as the day wore on. Tuesday saw a larger area of rain develop in the south and east through the day, with some particularly heavy bursts in the far southeast, but high pressure hung on across Greenland, keeping the rain out of northern England, Scotland, and Ireland.

Unprecedented heat over much of western North America and Canada sparked forest fires and even caused power cables to melt. - Credit: André Bessa (CC BY-NC-ND 2.0)

Outside of the UK, summer has been relentless so far. Much of Europe has been experiencing temperatures widely into the high 20s and low 30s Celsius (high 80s Fahrenheit), with parts of northern Greece and Albania approaching 40C (104F). Across the Atlantic, an “excessive heat warning” was issued across much of Arizona and California, and southern areas of Nevada and Utah. California in particular declared a state of emergency to address power system concerns as temperatures held widely around 43C (110F). Palm Springs recorded 51C (153F), Phoenix in Arizona saw 48C (118F), Las Vegas hit 46C (115F) and Furnace Creek Visitor's Center in the state's Death Valley National Park reached 54C (130F) on 17th June. Canada, too, was affected with Lytton in British Columbia hitting nearly 48C at the end of the month.

The “heat dome” that engulfed Canada and North America saw 103 heat records broken by the 28th of June, including Lytton's 47.9C. In La Niña years, cold water collects in the eastern Pacific and warm in the west, setting up an airflow that takes dense, tropical western air eastward, where it becomes trapped by an undulating jet stream. High pressure then keeps the air in place, akin to a lid on a saucepan, allowing temperatures to rise. Local variations in temperatures can then set up strong, dry winds that promote the spread of fire.

In India there has been a very mixed picture. The streets of Jacobabad in Pakistan hit 52C (126F), while Bangladesh was left reeling after Cyclone Yaas tore through at the end of May, only a week after Cyclone Tauktae killed 150 people. West Bengal chief minister Mamata Banerjee said some 20,000 homes were damaged in the state, with the town of Digha hit by 4m (13ft) high waves.

If you're interested in the wildlife to be found this month, including hoglets, nightjars, froglets, stag beetles and daisies, check out my Wildlife Watching - July article. If you happen to spot a stag beetle this summer, please take a moment to log it on the PTES Great Stag Hunt survey.

In the news

A few of the science and conservation news stories that caught my attention last month include a previously unknown extinction event, how jays aren’t easily duped and how wasps are precious rather than pesky:

New research on the diet of red foxes suggests they specialise more than we first thought. - Credit: Keith Williams (CC BY-NC-ND 2.0)
  • Elasmobranch extinction: We discover a new shark species, on average, every year, which highlights just how even in 2021 there's more to discover about the sharks in our oceans. New research by Catalina Pimiento and Nicholas Pyenson, published in the journal Science last month, suggests that sharks virtually disappeared from the oceans early in the Miocene, some 19 million years ago. We don't know what triggered this as it seems to be unconnected to any of the known global climate change or terrestrial extinction, but it appears to have set the stage for the evolution of the migratory shark lineages we're familiar with today.
  • Judicious jays: If there's one thing that Jonathan Creek and the Masked Magician have taught us, it's that knowing how magic tricks work leaves us feeling cheated, and the more elaborate the trick the bigger the disappointment. It would seem, however, that jays, those colourful members of the crow family, don't have this problem. A new study by scientists at the University of Cambridge has found that these canny corvids aren’t fooled by some magic tricks that dupe us, specifically those where we expect an object to move between hands.
  • Glaciers going: According to a recent report from a French-led team of scientists, the world's glaciers are melting at an increasingly rapid rate, increasing by nearly 50 gigatons of ice lost per year every decade. The melting of glaciers is an issue because it contributes significantly to sea level rise.
  • Wonderful wasps: Nemesis of a pint in a pub garden. Despoiler of picnics. There's little argument that stinging wasps are among the most hated of insects in the mind of the British public. They are, nonetheless, a significant part of our invertebrate fauna, with the UK's 2,500 or so species accounting for some 10% of all Britain's insect species. Now, a paper published in Biological Reviews argues that these ichneumonids are precious, not pests. The authors reviewed 500 papers on stinging wasp ecology and summarise how they provide huge benefits in the arena of pest control, helping protect an estimated £290bn-worth (€337bn/US$400bn) of crops from various worms and moths. Furthermore, their venom is a source of antibodies and there are at least 164 plant species that are completely dependent on wasps for pollination.
  • Finicky foxes? Foxes are incredibly adaptable mammals, turning their paws to almost every terrestrial habitat on earth, including some of our more populated urban areas. A key element in being able to survive almost anywhere is to not be picky when it comes to what you eat, and foxes are particularly catholic in their tastes. A recent stable isotope study suggests, however, that their diet in towns and cities may actually be more limited than that of their country kin. As well as finding that urban foxes ate more human-dominated foods, the research also revealed how individual foxes, whether in the town or city, specialised in particular food items. In other words, both town and country foxes appear to develop quite specific and narrow diets over time.

Discoveries of the Month

Sundered sciurids: little genetic mixing of red squirrel populations on the Isle of Wight

In the field of population ecology, island populations tend to be characterised by low numbers and low genetic diversity owing to isolation from others of the same species. This insulation can actually be an important driving force behind the evolution of new species, as they adapt to the specific conditions of their home, but it's not without its problems. Low genetic diversity means there's a smaller pool of resources to spawn adaptation in the face of adversity, the result being that any change in the habitat can result in extinction. Worse, without “new blood” coming in, the population can build up deleterious mutations that can hamper general survival, a phenomenon called inbreeding depression. Added to these issues, catastrophe can wipe out an entire species much more easily if there are only a handful of scattered groups. Consequently, conservation efforts tend towards connecting populations to increase gene flow.

New research suggests that the Red squirrel population on the Isle of Wight is becoming fragmented. - Credit: Peter Trimming

Britain’s flora and fauna are substantially impoverished, despite the efforts of many charities, volunteers and organisations to try and redress some of the balance. In recent years, there has been a shift in conservation thinking towards habitat protection, allowing the use of iconic species to help publicise and garner support for projects. Red squirrels (Sciurus vulgaris) are one such figurehead species, their decline having been well charted over the past 80 years or so, partly in response to the introduction and spread of the North American Grey (Sciurus carolinensis).

The current state of play of Red squirrel conservation in Britain is a patchwork of fragmented strongholds, largely in northern England and Scotland. In the south, the only remaining populations persist in parts of Wales, Jersey and three of our south coast islands: Brownsea, Furzey and the Isle of Wight. The population on the latter of these is the largest, with an estimated 3,300 animals inhabiting some 38,000 hectares (93,900 acres), and while the island offers reasonable protection from invasion by Greys, new genetic data suggest the populations of Reds here are becoming isolated from one another.

Isle of Wight squirrel biologist Helen Butler manages the Wight Squirrel Project, aimed a monitoring the island's population of Reds with the help of the public. People are encouraged to report sightings of dead squirrels and, where possible, they're submitted for autopsy. Between 2013 and 2018, ear tissue samples were collected from dead squirrels and subjected to microsatellite DNA analysis. In a paper currently in press with the journal Conservation Genetics, a team including Butler and led by Bournemouth University's Emilie Hardouin presents the results and compares their DNA data with those from the Isle of Arran (an island off the south west coast of Scotland), Brownsea, and Germany.

Hardouin and her colleagues found that, perhaps unsurprisingly, Wight squirrels were more closely related to those on Brownsea than Scottish or continental animals. More importantly, however, not only did the data show clear fragmentation of red squirrel populations on the Isle of Wight, it also revealed low gene flow between the east and west of the island. In their paper, the authors suggest this east/west split is likely a reflection of the habitat on the island:

Most of the larger patches of woodland, which are most likely to harbour larger populations of squirrels are situated to the East and West, with only small, isolated woodlands in the centre which was found to represent a barrier to gene flow.”

Red squirrels are more arboreal (they spend less time on the ground) than Greys and, as such, populations can be more prone to habitat fragmentation. - Credit: Marc Baldwin

The researchers point out that more data is required on the best way to connect these habitats in a way that Red squirrels are likely to feel comfortable using. This is an increasingly pressing requirement given that some inbreeding was detected among squirrels in the eastern population.

Source: Hardouin, E.A. et al. (2021). Wildlife conservation in a fragmented landscape: the Eurasian red squirrel on the Isle of Wight. Cons. Gen. In Press. doi: 10.1007/s10592-021-01380-z.

Field vs. forest: roe deer tick burden varies according to the habitat

Even the thought of being bitten by a tick is enough to have most of us putting on an extra layer, and this is a concern in the forefront of the minds of those who spend a lot of their time working outdoors. People often question what the “purpose” of ticks is, and while it's not necessary for something to have a purpose to have evolved (or exist), they are an important food source for a number of reptiles, birds and mammals. Even their capacity to spread disease, Lyme disease specifically, is part of the naturally unconscious management of animal populations in nature.

One consequence of climate change continuing apace is, we’re starting to think, that the hotter drier summers and milder wetter winters will aid the proliferation and spread of ticks in the northern hemisphere. In recent years we have certainly observed an increase in reports of ticks, with cases of tick bites and infection similarly on the rise. Indeed, a recent survey suggests cases of tick-borne Lyme disease in the UK may be three times higher than previous estimated, putting the annual number of cases as high as 8,000. In a bid to get a better understanding of this growing threat, scientists continue to study how tick population density varies with habitat and recent research in Scotland suggests high tick numbers in some open, treeless island habitats.

New research from Poland suggests that Roe deer living in woodland habitats carry higher tick burdens than those frequenting fields. - Credit: Marc Baldwin

Knowing where ticks are is one piece of the puzzle, but we also need to understand how they move around and, particularly, how their hosts may assist in that. Along those lines, a team of Polish scientists recently assessed the parasitisation of Roe deer (Capreolus capreolus) by Castor bean ticks (Ixodes ricinus), the most common human-biting tick species in Europe.

One hundred and sixty Roe deer of both sexes from the Wielkopolska Region of central-west Poland were assessed for tick burden by the researchers. Only 31 ticks were found on the 13 infested does assessed and so attention was focused on the bucks. When looking at the maturity of the 1,579 ticks recovered from the bucks, 99.97% were adults. We know from other studies that early in their lifecycle ticks parasitise small mammals, before moulting to their adult instar that feeds on larger mammals, although the sampling methodology here could equally account for so few larvae being found.

The bucks were grouped into one of the two ecotypes that exist in the region: the forest deer, which use woodland almost exclusively and seldom, if ever, venture into open fields; and the field deer, which do not appear to use woodland. When pooling all the data, tick occurrence was significantly higher among forest deer than those using open fields – three times higher. Writing in the journal Scientific Reports at the end of May, the biologists caution that despite forest deer being more significant reservoirs for ticks, field deer have more potential to transmit them to people:

European roe deer living in forests have fivefold higher number of ticks and threefold higher probability of tick infestation than ones living on fields. However, still 60% of field roe deer ecotype carried at least one tick. This finding is important from a public health point of view. European roe deer living on fields spread the ticks to areas in close vicinity to human settlements.”

Source: Opalińska, P. et al. (2021). Fivefold higher abundance of ticks (Acari: Ixodida) on the European roe deer (Capreolus capreolus L.) forest than field ecotypes. Sci. Rep. 11: 10649. doi: 10.1038/s41598-021-90234-2.

Related reading