Seasonal Update - March 2020

The winter of 2019/2020 was among the mildest and wettest on record, with February seeing more than twice the expected monthly rainfall in England and Wales. As such, many rivers burst their banks, such as the River Blackwater here in Southampton. - Credit: Marc Baldwin

Congratulations on making it through winter and into spring. There were times last month when it felt like we might all be washed away. February saw the UK battered by two deep areas of low pressure that brought strong winds and torrential rain to already saturated ground, resulting in widespread flooding. The jet stream has been exceedingly strong this winter, with winds topping 260mph in February, courtesy, in part, of a record positive Arctic Oscillation that spun up the deep low pressure systems which spawned the named storms “Ciara” and “Dennis”.

The second weekend of last month saw the arrival of storm Ciara, named by the Irish Metrological Office, one of the most powerful storms we’ve ever seen, with winds approaching 110mph in parts of western Wales and Scotland. Even here on the south coast we saw winds reach nearly 75mph. Many parts of northern England and Wales were deluged with rain that caused serious flooding, falling as it did on ground that was still saturated from the wet autumn.

Almost a week exactly after Ciara hit, storm Dennis brought more wet and windy weather. While the winds were slightly weaker than Ciara, very heavy rain exacerbated the flooding left in Ciara’s wake. Indeed, parts of Wales saw a month’s worth of rain fall over the weekend. Worse was that Dennis was extremely slow moving and fragmented, meaning that fronts brought rain over several days, even after the worst of the storm had passed on the Sunday afternoon. The village of Capel Curig in north Wales, for example, received a further 36 mm of rain in 12 hours on the Wednesday; that’s nearly 40% of the total rainfall they’d expect for the whole month in just half a day after Dennis had passed through.

Many homes in Worcester were flooded in February 2020 when the River Teme burst its banks following storms Ciara and Dennis. Similar scenes were replayed across the UK last month at an estimated cost of nearly £250 million. - Credit: Dave Grubb

We drove home from Cornwall on the Sunday afternoon as storm Dennis moved north, and every river we passed over had burst its banks. In the UK as a whole, river levels in the Colne, Ribble, Calder, Aire, Trent, Severn, Wye, Lugg, and Derwent all set new records last month and, at the time of writing, 112 flood warnings are in place, including six severe alerts for a danger to life close to the Welsh border. The month ended on a wet and persistently windy note; very mild in the south, and cold, with some disruptive snow falls, in the north.

On the other side of the world, Australia also experienced copious rain. Many places saw flash flooding, including Sydney, but the rains did at least help to extinguish the bush fires that had been burning out of control for several weeks. Similarly, heavy rainfall in the Horn of Africa provided ideal breeding conditions for locusts; Kenya, Ethiopia and Uganda have been badly affected and the Somali government declared a national emergency. We should expect these events to become more common as the climate continues to warm, because warm air can hold more moisture than cold air.

In Australia, heavy rain has provided some respite from the devastating bush fires that have burnt for much of their summer, but have caused flash flooding and landslides in some areas. Credit: Sky News Australia

I mentioned last month that January was the warmest on record, but February saw some temperature records of its own. Spain reached almost 30C (86F) last month and Antarctica’s Seymour Island recorded its highest temperature, nearly 21C. At the same time, on 10th February, the Mauna Loa observatory in Hawaii recorded unprecedented levels of CO2 in the atmosphere, peaking at 416.08 ppm. Climate scientists think that this CO2 content has been exacerbated by emissions from the bushfires in Australia.

If you’re up for getting outside, as usual, the Wildlife Trusts have a series of nature-themed events up and down the country, as do the RSPB. If you feel like being proactive this month and live near the coast, Surfers Against Sewage is looking for people to organise cleans of their local beaches – details here. The Forestry Commission is running a series of events this month – full list here. If you’re interested in the wildlife to be found this month, check out my Wildlife Watching - March page.

In the news

Some of the environmental news that’s caught my attention this month includes plastic recycling, tiger sharks, sperm whales, and methane.

  • The Dutch recycling firm Fuenix Ecogy has signed a deal with US materials giant Dow Chemical Co, based in Michigan, to supply them with feedstock made from recycled plastics that they will use to make new polymers, closing their “plastics loop”. At the same time, in Germany, EPEA Hamburg and the Karlsruhe Institute of Technology are working with chemical company BASF to use a process known as “depolymerization” to break down and reform plastics, allowing them to make new products from the recycled materials.
  • A series of rather gruesome photographs showing tiger sharks caught on large metal hooks attached to drumlines off the Australian coast has sparked calls for the hooks to be banned. The hooks, buoyed off the Queensland coast, are used as part of a shark deterrence programme, aimed at reducing or preventing shark attacks on bathers, but they’re estimated to have killed at least 9,000 tiger sharks (Galeocerdo cuvier) since 1962, some 75% of the estimated population in Australian waters.
  • Scientists at the University of Otago in New Zealand have found that earthquakes disrupt the ability of sperm whales (Physeter macrocephalus) to find food. Earthquakes and aftershocks send out large vibrations that can disorient the whales and even cause hearing damage. They also causing underwater landslides, both moving the benthic fauna and changing the landscape, forcing the whales to refamiliarize themselves with it. Following the 7.8 magnitude quake at Kaikōura canyon in 2016, the scientists found that sperm whales spent about 25% more of their time at the surface, suggesting they were having to spend longer looking for food.
  • New research from scientists at the University of Rochester suggests that humans have been releasing far more methane into the environment than previously thought. The researchers measured samples of air trapped in ice cores from Greenland and found almost all of the methane emitted to the atmosphere was biological in nature until around 1870, marking the start of the human industrial revolution during which our use of fossil fuels increased significantly.
New research suggests that earthquakes may interfere with the feeding of sperm whales. - Credit: Gregory "Slobirdr" Smith (CC BY-SA 2.0)

On the site

You may have noticed that the first in a new series of blogs started on the site around the middle of January. The Walks with the Camera blog, as the name implies, describes some of my early morning nature walks, most around the New Forest in Hampshire but also some around Cornish county lanes. Inspired by positive feedback I had when they originally appeared on Facebook and illustrated with photos taken during the walk, I hope they’ll provide an interesting new feature to the site. Get yourself a cuppa and a biscuit and join me for a walk in the woods.

As well as a new blog series, I have now completed an in-depth Q&A about fox scent marking behaviour that’s in the final stages of proof reading. This Q&A is intended to try and answer the question of why foxes are (to many people) so infuriatingly smelly, and has been in preparation for a long time. Now it’s out of the way I intend to make a few minor updates to the current species bios and will then start working on the next new species bio – the Chinese water deer.

Discoveries of the Month

Just stepping out, deer: long-distance dispersal in Sika deer

Japanese sika deer, such as this stag photographed in the New Forest, are an introduced species and generally considered invasive. New tracking data suggest this species is capable of very long distance dispersal, a feature that presumably helps explain their expanding distribution here in Britain. - Credit: Keith Talbot

Britain has its fair share of introduced species and anyone acquainted with our deer fauna will likely be aware that five of the seven species found in the UK today have their origins elsewhere. Most of us are now familiar with the small Reeves’ muntjac (Muntiacus reevesi), which has spread throughout most of the country, even now found in parts of Northern Ireland, since its introduction to Britain in Bedfordshire during the nineteenth century. Perhaps less familiar, being less widespread, is the sika deer (Ceruvs nippon), which was introduced to Britain from Japan around 1860 and is now found in scattered populations across the country, including England and Ireland, with the largest populations in Scotland.

Sika deer can be an issue here for several reasons, perhaps the most important of which is their propensity to interbreed with red deer (Cervus elaphus). For this reason, deer managers aim to keep the species apart and ultimately limit their spread, but that’s easier said than done. Sika deer tend to be far less fazed by human activity than reds, which means they have significant potential for dispersal, thinking nothing of crossing parks and gardens during the daytime. Tracking studies in their native Japan have also shown that they can disperse considerable distances. One study monitoring GPS-collared deer between 2008 and 2010 found, for example, one of their young males moved from their study area to Kawakami Village, some 40 km (25 miles) away. More recent data, also from Japan, suggest, however, they can move much further than this.

In November 2014, Akiko Takii at Shinshu University’s Institute of Mountain Science and colleagues caught and radio-collared a five-month-old male sika deer calf near Omachi City. Come May of the following year, at the age of 11 months, the calf left the summer range and entered what Takii and his team refer to as a “vagrant stage of dispersal” that lasted 111 days. At the end of this four-month nomadic stage, the stag settled in the eastern foothills of Mount Ontake. As the crow files, Mt. Ontake is some 74km (46 miles) from Omachi, but the GPS track shows that the deer actually travelled a staggering 131 km (81 mi.), the longest dispersal distance thus far reported for a sika deer. The deer also seemed to follow a determined path, never back-tracking, and, in their short paper to the journal Mammalia earlier this year, the researchers note:

The actual dispersal distance was greater than the linear distance, which indicates that the dispersal path was nonlinear; however, the deer never returned to his prior stopover sites and always headed southward.”

These data illustrate how this species can be highly mobile, moving long distances in relatively short periods, and may help explain their increasing spread within Britain.

Source: Takii, A. et al. (2020). An initial record of a long-distance dispersal route of a male sika deer in central Japan. Mammal. 84(1): 63-68.

Hedgehog Green Cross Code: understanding hedgehog vulnerability to roads

The continued expansion of the human population has dominated discussions around the environment and climate change in recent years. The global population is rapidly approaching the 8 billion mark, growing at about 1% per year according to Dadax’s “Worldometer” algorithm. In Europe alone the population has grown by between 0.1% and 0.2% every year for the past decade, and the UK now sits 21st in the population rankings. With this increase in people comes increasing urbanisation. Globally, it is estimated that just over half the population is urban, with the relative percentages higher in the UK (83%) and across Europe (75%) as a whole.

Traffic represents a significant danger to hedgehogs, with roads adding to an already fragmented habitat. - Credit: Marc Baldwin

Urban living conveys many benefits to us, but frequently comes at the expense of the natural landscape and its associated wildlife. Alongside habitat loss, a particular problem for many animal species is the construction of roads. In Europe, an estimated 70,000km (43,500 miles) of roads are built each year and Britain alone has seen an average yearly increase in traffic of around 10% since 2000, a figure predicted rise still further by 2050. Roads can stress animals, bringing noise and pollution to habitats. They can also be a direct, and significant, source of mortality, particularly where relatively fast roads fragment wooded habitat.

For those species that seem to have found a refuge in our towns and cities, roads can be a major threat. Evidence has been building for around a decade now that hedgehog populations seem to fare better in urban areas than on peripheral farmland, particularly arable farms. But town and city living means more contact with traffic. In 2016, David Wembridge and colleagues estimated that as many as 335,000 hedgehogs may meet their maker on Britain’s roads each year, and studies across Europe also point to high levels of mortality. Recently, a team of UK-based biologists, led by Patrick Wright at the University of Sussex, have employed some computer modelling techniques to try to understand what might make hedgehogs more susceptible to being run over.

The researchers gathered data on hedgehog roadkill from a variety of citizen science projects in Britain, including the Big Hedgehog Map, Mammal Mapper, Mammal Tracker and Mammals on Roads, as well as from the National Biodiversity Network gateway and other wildlife monitoring schemes. In total, they collected 12,684 records of hedgehog roadkill reported between 1959 and 2018 and fed them into a couple of mathematical models that factored in the UK’s 400,000km (250,000 mi.) of roads. They used a Generalized Additive Model to look for seasonal trends in the data and a sequential multi-level Habitat Suitability Modelling technique to see if there were any types of habitat where hedgehogs were more like to be killed.

Unsurprisingly, the GAM modelling revealed a strong seasonal trend in roadkill; lowest in winter, when hedgehogs tend to be hibernating, and highest in summer (peaking in July), when they’re at their most active. Of perhaps more interest was that hedgehog susceptibility to being run over was linked to a combination of environmental and abiotic variables, with the areas of improved and rough grassland, urbanisation and road density the most important elements. In particular, major roads appear to pose more of a threat than B roads or minor roads.

Hedgehogs are very susceptible to traffic collisions and drivers should be most vigilant for hedgehogs in July on roads surrounded by a mix of urban and grassland cover, according to new research. - Credit: Mark Fletcher (CC BY-NC 2.0)

Roadkill is likely throughout towns and villages, but heavily associated with suburban areas of larger cities where grassland is more likely to be found. Overall, however, only 9% of the British road network was identified by the models as being “high risk” to hedgehogs, giving ecologists and planners somewhere to focus efforts. These, largely suburban areas, were particularly prevalent in central Britain, southern Wales, the outskirts of London, and the Central Belt of southern Scotland. Writing in the journal PeerJ last month, Wright and his colleagues urge:

“… that drivers should be most vigilant for hedgehogs in July on roads surrounded by a mix of urban and grassland cover.”

Source: Wright, P.G.R. et al. (2020). Predicting hedgehog mortality risks on British roads using habitat suitability modelling. PeerJ. e8154. DOI: 10.7717/peerj.8154.

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