Arts, Books, Environment, Nature

Book Review: Hedgelands

LITERARY REVIEW

Intro: Hedges are humble habitats that are a lively host to much wildlife – a secret safari providing a plethora of environmental benefits

THE humble and often-neglected British hedge, is described by author Christopher Hart as “an incredibly porous and self-sustaining feature of our countryside . . . one of the happiest accidents in human history.” It hums with bees and butterflies, is a rich haven for insects, birds, hedgehogs, shrews, voles, and bats, and also acts as a windbreak, stock fence, flood defence system, and an environmental barrier against soil erosion. The RSPB agrees; its research shows that hedges may be supporting up to four-fifths of our woodland birds, half of our wild mammals, and a third of our butterflies.

Hedges have been a feature of the British landscape since the Stone Age. The original ones were “dead hedges”, made from piles of branches and brushwood collected from cleared areas of woodland.

As the wood rotted, it was swiftly colonised by fungi and insects. Passing birds excreted seeds from trees and shrubs – such as hazel, oak, ash, hawthorn, dog rose, blackthorn, and bramble – which soon started sprouting in among the dead wood. From there, a living hedge was born. (A hedgerow, if you were wondering, is a hedge that includes features such as banks, trees, walls, fences, or gates.)

Our ancestors soon learned the best way to deal with an unruly hedge: by cutting half-way through a rising trunk and then to lay it back into the hedge sideways. In time, this creates a barrier so dense and tough that it can even hold back an amorous bull trying to get into a field of cows.

Yet as Hart rightly points out, these ancient hedges are much more than just a physical barrier. They mitigate flooding and soil erosion and give many animals an invaluable source of shelter from precipitous conditions. A hedge will protect smaller birds and mammals from predators like crows, magpies, sparrowhawks, and foxes – a dense hedge is difficult for predators to access and manoeuvre. This “narrow but incredibly complex ecosystem” is also an abundant source of food for wildlife, providing hips, haws, sloes, and blackberries for them to feast on.

Many of the countryside hedges we see today pre-date the Georgian era, some even being Anglo-Saxon. In a county like Devon, where the land is suited to sheep and cattle and less likely to be ploughed, at least a quarter of the hedges date back to Norman times.

TWO

THERE are strong regional variations in Britain’s hedges. In the Midlands, traditionally cattle country, hedges tend to be mainly hawthorn, which is an excellent barrier to bullocks. The high rainfall in Wales and Ireland is just the thing for blackthorn, which happens to be a handy plant for snagging and restraining sheep.

The Somerset Levels typically have hedges made of osier, a small willow tree, while in Kent and Worcestershire you’ll find hedges of beech, poplar, and elder which tend to grow tall to protect prized orchards from the wind.

By 1820, there were 700,000 kilometres of hedges in England (and many more in Scotland, Wales, and Northern Ireland). Today the figure is 400,000 which still sounds impressive, but many of these hedges are so degraded that they have become “little more than a blunt, dwarfish lined of scarred and wind-scoured stumps”, as Hart writes despairingly.

On arable land, hedges are often seen as an obstacle for tractors, while on pastureland, farmers find it easier to put up a barbed wire fence than have a hedge separating livestock. Hart is sympathetic to farmers, who are not “the cartoonish villains of the countryside but, rather, hard-pressed food producers just trying to stay in business”.

But there’s no denying that replacing a bountiful hedge with barbed wire is a disaster for wildlife, which results in “no wild foods, berries, nuts, wild greens, or herbs . . . no shelter or habitat for birds and mammals, [nor] beneficial pollinators and insect predators.”

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MOST of the damage to the country’s hedges was done from the 1960s onwards when, incredibly, government actually offered subsidies for their removal. After 1973, the EU’s damaging Common Agricultural Policy was even more zealous in paying farmers to destroy ancient hedges.

If all this sounds depressing to anyone who cares about the countryside and its wildlife, Hart offers some practical solutions. Many hedges in private gardens are a single variety, like privet or beech; the author suggests that you rewild yours, by weaving honeysuckle and brambles through your hedge, making it far more attractive to insects.

And if you leave a little verge around the bottom of your hedge, all sorts of wildflowers might pop up, from orchids and buttercups to cow parsley and bluebells.

Above all, we are urged to cherish our existing hedges. Instead of spending a fortune on planting millions of new trees, which Hart says are “of low ecological value”, he would like the Government to allocate a fraction of that money to restoring hedgerows.

With better management of hedges, “we might not need to worry so much about insects disappearing, bird numbers falling or our targets for carbon capture. Our lovely native hedgerows would do much of the work for us, if we only look after them.”

Hart has his own 300 yards of “beautiful, unkempt, pullulating hedgerow” at his home in Wiltshire, and he has seen for himself how endangered birds such as redwings and fieldfares will eagerly flock to a hedge which provides nutritious wild berries for them.

Christopher Hart has written an eye-opening and inspiring book which will leave the reader with a deep appreciation of these wonderful habitats – and perhaps a desire to create their very own hedge. As he says: “You don’t need to go to the Serengeti to see amazing animals. You just need a good thick hedge.”

Hedgelands by Christopher Hart is published by Chelsea Green, 208pp

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Environment, Science, Technology, United States

Ammonia is being developed as a low-carbon fuel

ENVIRONMENT

Intro: A start-up in America is developing world’s first ammonia-powered ships

THE Brooklyn Navy Yard’s sprawling industrial complex once employed 70,000 workers to build US battleships and aircraft carriers during the second world war. Almost 80 years later, it has become home to a New York city firm with a very different maritime mission – harnessing ammonia as a low-carbon fuel for the global shipping industry.

The start-up Amogy has already shown how ammonia-powered technology can work in a flying drone, a John Deere tractor and most recently a truck. Now, it is working on an ammonia-powered ship.

Most ships currently run on fossil fuels that emit greenhouse gases, accounting for 3 per cent of the world’s carbon emissions. One alternative involves converting vehicles to hydrogen power that would only emit water. But hydrogen gas needs to be compressed and liquified at -253°C for storage and transportation.

Ammonia could serve as an alternative hydrogen-bearing fuel that is more easily stored and transported in a stable liquid form at room temperature.

Hydrogen can be extracted by heating ammonia to high temperatures, which is a process that comes with its own energy cost. This is where Amogy’s technology comes in. To make ammonia power more viable, the company has developed what it describes as a more efficient and miniaturised “ammonia cracking” method that can chemically extract hydrogen from ammonia at a lower temperature. It uses a proprietary catalyst to speed up the process inside a chemical reactor that feeds into a hydrogen fuel cell.

A leading chemist at Saint Mary’s College of California says that what Amogy was able to bring to the table is that by having better catalytic technologies (all proprietary) they were able to miniaturise their ammonia cracking units and put them on board vehicles.

It was in July 2021 when Amogy first showed that its system could supply 5 kilowatts of power to a drone. By comparison, a standard ammonia cracking system for extracting that amount of hydrogen power is usually the size of a large shipping container. It also paved the way for a 100-kilowatt tractor demonstration in May 2022. That was followed by a 300-kilowatt truck demonstration in January 2023. The firm is now working towards demonstrating a 1-megawatt system in a tugboat.

Many countries already have pipelines and port facilities for handling ammonia that is produced industrially as fertiliser for agriculture. The US alone has more than 5000 kilometres of ammonia pipelines compared with 2500 kilometres of pipeline for transporting hydrogen – though it will need more to support ammonia-powered vehicles.

Another challenge is that ammonia still “has a carbon footprint associated with the production” because the standard industrial process uses natural gas. Low-carbon ammonia production would require use of carbon capture.

Cleaner alternative methods could ideally use electricity from renewable power sources to split water into hydrogen for conversion to ammonia.

. Science Book: Chemistry

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Environment, Research, Science

Migrating animals: How do they find their way?

ETHOLOGY

Intro: The ability by some animals to find their way when migrating over long distances intrigues and amazes us. The puzzle of how they do this is difficult to solve and we are only really just beginning to find answers

SOME of the migratory habits of animals are truly astonishing, not least because without our own navigational aids, our compasses and our GPS systems, we very easily get lost ourselves. Arctic terns leave their northern breeding grounds in and around the Arctic Circle towards the end of the summer to fly south all the way to the Antarctic coast, arriving in time for the onset of summer in the southern hemisphere, and then fly all the way back to the Arctic to breed the following spring. If the terns flew directly between their two destinations, this would involve journeys totalling over 32,000 km (20,000 miles), but they actually adopt much more convoluted routes, increasing the distances they cover by tens of thousands of miles. Yet after covering such enormous distances, the terns often return to the exact spot where they bred the previous year.

Atlantic salmon spend most of their adult lives in the ocean before returning to the same river where they were born, and usually to the same stretch of that river, to spawn. Some monarch butterflies are involved in a circular migration – which takes several generations to complete, travelling from southern Canada to overwintering sites in central Mexico while every year, millions of Christmas Island crabs travel from the forest in the interior of their Indian Ocean island to the coast to breed. Several species of frogs and toads engage in similar annual mass migrations, and sea turtles such as loggerheads and leatherbacks give the impression of being engaged in a lifelong migration, swimming for what can be thousands of kilometres between breeding grounds on beaches and feeding grounds in the distant ocean.

Navigating animals

These birds, fish, butterflies, crabs and turtles provide a few examples from among the thousands of species of animals that engage in migratory behaviour of one sort or another. Charles Darwin thought that animals, and to some extent humans as well, possessed an instinctive ability to orientate themselves in their surroundings, which they could use to navigate by dead reckoning, but he could not be any more specific about how this ability worked. Beginning in the 1910s, the Austrian animal behaviourist Karl von Frisch carried out experimental research on honeybees, which showed that their primary means of navigation involved using the position of the Sun to orientate themselves, but that they could also detect and follow the pattern of ultraviolet light in blue skies, which is caused by polarisation and is invisible to human eyes. On cloudy days, Frisch found that the bees could also make use of the Earth’s magnetic field to find their way when the Sun and polarised light were not visible. He would also be the first to describe the so-called waggle dance that the bees engaged in as a means of communicating the location of a source of nectar they had found to other bees in a hive.

Since Frisch’s work, which earned him a Nobel Prize in 1973, other animals, such as sea turtles, have also been found to be able to detect the Earth’s magnetic field. Homing pigeons, which can return to their own lofts after being released hundreds of kilometres away, appear to use the magnetic field as one of a range of navigation techniques. Attempts have been made to discover how pigeons detect the magnetic field, which is actually very weak, and while we do not know for certain, one theory suggests they somehow make use of particles of magnetite, a highly magnetic mineral of iron oxide found in the upper part of their beaks. Even so, it remains a mystery how the navigational information that may be gained in this way is passed to the brain and processed.

Homing pigeons can switch between different methods of navigation as circumstances dictate, sometimes following known landmarks, such as coastlines, rivers and roads, while at others navigating by the Sun and stars. When it is too dark or cloudy for them to see the sky, they can fall back on finding their way by following the magnetic field. Researchers at the University of Texas who monitored the brain activity of pigeons while they were subjected to a moving magnetic field came to the conclusion that, as well as having compasses in their heads, the pigeons somehow constructed maps in their brains as they went along, so when they ended up in a place they had never been before they could head straight for home. We may like to think of ourselves as rather more intelligent than pigeons, but, for all our superior brainpower, we can’t do that.

Alternative theories

Research into the ability of European robins to use the Earth’s magnetic field to navigate suggests that the mechanism involved may work at a subatomic, or quantum, level. If this proves to be the case, then it would go some way to explaining how animals can detect and make use of the natural magnetic field, which is far too weak to provide enough energy to power any molecular chemical reactions. Magnetoreception, as this ability is known, appears to function through the eyes of the robin, so it is possible that light provides the energy required to activate so-called radical pairs, subatomic charged particles that are small enough to be influenced by the low levels of magnetism and may create some form of navigational signal that is then passed to the robin’s brain via the optic nerve.

See also:

. Book Review – ‘Greenery: Journeys In Springtime’

. Science Book

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