Category Archives: Science

Arts, Environment, Government, Health, Science, Society, United Nations

How Can We Deal With Global Population Growth?

POPULATION GROWTH

Intro: With population numbers projected to continue to swell over the course of the twenty-first century, there are some pressing questions that remain unresolved. We should turn to science in search of solutions to Earth’s depleting space and resources.

THE subject of global population growth can be an emotive one, and many accounts of rising populations are accompanied by dire warnings of impending catastrophe. Concern about population growth is by no means a modern phenomenon, though. In 1798, the British cleric Thomas Malthus published An Essay on the Principles of Population, in which he addressed the potential problems that could develop due to the rapidly rising population in Britain at that time, a consequence of the Industrial Revolution. He argued that populations had the capacity to grow more quickly than food production, writing, “The power of population is so superior to the power of the earth to produce subsistence for man, that premature death must in some shape or other visit the human race.” It would become a highly influential concept and one that would reach beyond demography alone – acknowledged, for instance, by Charles Darwin as having been one of the key ideas that led to his theory of evolution by natural selection, which described competition for resources as being one of the driving forces behind evolution.

The Population Bomb

In 1968, the American entomologist and environmentalist Paul Ehrlich wrote in Malthusian terms in The Population Bomb of an upcoming catastrophe, in which many millions of people would die of starvation. Though not the first publication to examine the so-called “population problem”, its popularity introduced the issue to a much wider audience. It was followed in 1972 by the even more widely read The Limits to Growth, a collaborative report commissioned by the political think tank the Club of Rome. Both works were relatively sober, informed assessments, but were followed by a range of sensationalist books and articles, containing various prophecies of doom – which remain a feature of environmental discussion today.

Paul Ehrlich

Paul Ehrlich, whose book brought the population problem to the attention of a much wider audience.

In The Population Bomb, Ehrlich wrote that the Earth could support two billion people before disaster ensued – a figure that had already been exceeded by more than a billion at the time the book was published. Now, almost 50 years later, the predicted catastrophic collapse has not occurred (at least not yet anyway). In July 2015, the Population Division of the United Nations Department of Economics and Social Affairs in New York released the annual revision to its 2010 population census, providing estimates of the global population over the course of this century. According to this, the global population was 7.3 billion in 2015, and was expected to continue growing, reaching 10 billion by the middle of the century and 11.2 billion by 2100, by which time the rate of growth is expected to have slowed – before stabilising and perhaps beginning to fall.

By no means do all demographers agree with the UN figures. The wide variation between experts’ population predictions is a consequence of the number of unknown factors involved, and because in reality people rarely behave exactly as expected. But, if we take the UN figures as a reasonable estimate, over the next three to four decades an additional 3 billion people will inhabit the world, and the total figure will be five times higher than Paul Ehrlich’s estimated carrying capacity of the Earth.

The Impact of Science

One of the ways science has helped to avert potential disasters is through agricultural research aimed at increasing food produce. One of the best-known examples of this is the Green Revolution on the Indian subcontinent, which began in the 1960s – a period when India and Pakistan were experiencing population booms that appeared to be outstripping the capacity of the region’s agriculture to produce enough food for everyone. New varieties of high-yielding wheat, developed by the American agronomist Norman Borlaug at a research station in Mexico, were transferred to the subcontinent, greatly increasing agricultural productivity and averting the potential for widespread famine.

Subsequent research produced new varieties of other staple crops, including rice, and these, together with the use of new technologies in the shape of farm machinery, fertilisers and pesticides, have had a dramatic impact on the amount of food produced – even if these technical advancements can come with social and environmental costs. It has become clear that new technology on its own is not a complete solution, though, and extreme poverty can lead to people remaining malnourished despite there being no local food shortages, through not having land to grow crops themselves or the means to buy enough food.

Science can also help in the field of healthcare, through the development of medical technology and drugs that address the particular problems causing high levels of child mortality, which are often encountered in those parts of the world where high rates of population growth occur. When such technologies are combined with more widely available healthcare services, the resulting reduction in child mortality often leads to lower rates of population growth. Put simply, women have fewer children in places where those children are more likely to survive into adulthood, and so population numbers gradually begin to stabilise.

Hope For The Future

The UN figures show that growth rates have already slowed down in many parts of the world. Europe, North and South America and Oceania now show no growth at all, and nor does much of Asia, with the notable exceptions of India and Pakistan. About three-quarters of the population growth set to occur over the course of this century is projected to be on the African continent, and this rise will almost all be as a consequence of people living longer, rather than an increase in the number of children being born. This statistic is key to gaining an understanding of how population growth should slow down and eventually stabilise in the future; improvements in healthcare initially lead to a rapid rise in life expectancy, so, rather than a rising population being caused by more children being born, it is actually a consequence of there being an increased number of older people. Over time, the initial rapid increase in life expectancy will tend to level off and, at this point, the population will stop rising as well.

 

IN the future, then, there will be many more people in the world, and it does appear that population growth is set to continue in the long term. The challenges ahead are to grow enough food, to alleviate extreme poverty and to provide adequate healthcare for the entire global population.

Alternative Theories

UNLIKE the doom merchants who have until recently dominated the public debate on population growth, the Swedish doctor and statistician Hans Rosling describes himself as a possibilist, believing not only that the Earth can support 11 billion people, but that all of them can enjoy a good quality of life. He appears to be on a mission to make population statistics entertaining as well as informative, making use of dynamic graphics to illustrate his lectures and enlivening proceedings with plenty of comical jokes, mostly at his own expense.

To take just one example of many, Rosling describes the washing machine as being one of the great inventions of the twentieth century because of the impact it has had on freezing women from domestic drudgery, allowing them the time to do other things, like going to university or by seeking an alternative career. As he points out, the statistics show that as women become better educated, they gain more control over their lives – over the age at which they start a family and the number of children they have. Where they have the choice, many women opt to have children later in life than their mothers and grandmothers did, and often prefer to have two or three children rather than five or six. This phenomenon has been seen around the world and has often occurred over the course of a single generation. Rosling is not trying to say that this is entirely caused by the washing machine, rather using it to illustrate the point that the empowerment of women has been one of the driving forces behind the observed reduction in population growth rates.

Standard
Research, Science

Why does the Earth’s magnetic field reverse?

GEOPHYSICS

Intro: One of the properties of our planet that we have struggled to explain is the fact that its magnetic field occasionally reverses. If this happened today, it would mean that our compasses would point to the south, rather than to the north.

A reversal in the magnetic field is probably not something we need to get overly worried about because the last full one occurred 780,000 years ago, while a partial reversal, known as a geomagnetic excursion, last happened 41,000 years ago – when the poles reversed for a few hundred years before flipping back again. The generally accepted theory of how the Earth’s magnetic field is generated states that heat from the solid inner core of the planet causes chaotic and swirling convection currents in the liquid outer core, and, as it is predominantly composed of magnetised iron, this rotational movement works like a giant dynamo, inducing a moving electric current, together with its accompanying magnetic field. The action of this geodynamo, as it is known, is thought to lead to the polarity of the planet and to maintain the magnetosphere, the region of space around the Earth to which the magnetic field extends.

The possibility of the magnetic field reversing was first proposed in 1906 by the French geologist Bernard Brunhes, after he had studied iron minerals in volcanic rocks from Auvergne, the region of central France well-known for its numerous extinct volcanoes. This was based on an anomaly he observed, in which some crystals of magnetic iron minerals in the volcanic rocks are orientated either to the north or south. Shortly afterwards, the Japanese geophysicist Motonori Matuyama carried out a systematic study of volcanic basalt rocks in different locations in Japan and China, which demonstrated that rocks in the same geological layers – ones that had been laid down at the same time – showed the same polarity, described as normal where iron minerals are oriented to the north, and reversed in those pointing south.

The volcanic landscape of the Massif Central in the Auvergne, France.

Matuyama’s work provided clear evidence to support the theory that the poles had reversed in the past, but it did not receive any great attention until the 1950s, when radiometric methods of dating rocks based on the decay of radioactive isotopes were developed, which allowed a chronology to be worked out. The pioneers of this field were later recognised, with their names being assigned to the periods, known as chrons, of normal or reversed polarity. We are currently in the Brunhes Normal Chron, which began 780,000 years ago, and this was preceded by the Matuyama Reversed Chron, beginning 2.59 million years ago, while the period during which the flip took place is called the Brunhes- Matuyama Transition. It used to be thought that this flip occurred over the course of thousands of years, but recent research, published in 2014, suggests that it could have been made quicker, perhaps taking as little as 100 years.

The Flipping Field

We don’t know what causes a reversal in polarity and may well have to wait until it happens again before we have the opportunity to study the phenomenon in enough detail to find out. We currently lack a clear enough understanding of what is happening in the outer core and mantle to generate the magnetic field in the first place, let alone know why it flips. Past reversals have occurred over an apparently random time frame, so it is impossible to predict when the next one will be. A gradual weakening of the magnetic field recorded over the course of the last century has led to some speculation that we are entering a transitional period, but, as we don’t know anything about the processes leading up to reversals, there is no way of knowing if this is really the case. A reversal may be beginning right at this moment, or it may not happen for hundreds of thousands of years.

 

One way of investigating reversals in the Earth’s polarity is to construct computer models of the way in which the Earth’s magnetic field is generated by the dynamo in the inner core, and then run simulations to see what happens. This involves attempting to recreate the interaction between the heat generated in the inner core and the convection currents thought to be the source of the magnetic field in the outer core, which, as we don’t fully understand what is going on in either region, is extremely difficult. One simulation developed by Gary Glatzmaier and Paul Roberts at University College, Los Angeles, in the 1990s, uses a complex set of equations, involving thermodynamics and fluid motion, to describe the physical properties of the geodynamo. It was found to provide an accurate model for the generation of known variations in the magnetic field, and, when run to simulate the changes occurring in polarity over hundreds of thousands of years, showed the process of reversal occurring on a number of occasions. The timing of the reversals was random, and apparently caused by the development of a particular set of circumstances, in which the thermodynamics and fluid motion evolved with the generation of the magnetic field in such a way as to weaken the strength of the poles. If the strength of the poles dropped below a certain point, this caused a reversal.

The Impact of Reversals

If computer-generated models accurately simulate what is happening in the outer core, and reversals are indeed caused by a weakening in the magnetic field, then this has implications for the ability of the magnetosphere to deflect potentially harmful high-energy particles found in cosmic radiation. If the magnetic field were to disappear completely, the planet could also be exposed to solar wind. This is thought by some scientists to have occurred on Mars, which does not have a magnetic field, and thus any atmosphere that may have existed would have effectively blown away. Needless to say, this would be disastrous for our planet, but as there have been numerous reversals in the past and the Earth still has an atmosphere, it is reasonably safe to assume that this scenario is not very likely to happen here.

 

Studies of transitional periods that lead to reversals and their impact on life on Earth have actually found nothing to suggest any harmful effects. There is, for instance, no correlation between the timing of reversals and extinction events or periods of increased seismic and volcanic activity. So it would appear that, beyond the disruption it would cause to our navigational systems, and the possibility of interference with some communications, we don’t have a great deal to worry about. There could be an impact on animals that make use of the magnetic field to navigate, though it would appear that reversals usually happen over the course of long enough periods to allow them to adapt. In the unlikely event of a flip suddenly happening tomorrow, aircraft may have to be grounded while we work out how to navigate, our phone services could be interrupted for a while, and homing pigeons might get rather confused.

Alternative Theories

In recent years, seismic images of the Earth’s inner core have been interpreted as showing it to be composed of slightly differing eastern and western hemispheres. One theory, known as translational instability, suggests that this difference is due to the growth of the core, caused by its cooling, being lopsided – with more iron crystallising out on the surface of the western side than on the eastern one.

In research published in 2012, Peter Olson and Renaud Deguen of Johns Hopkins University in Baltimore, Ohio, set-out to test this theory, by modelling what would happen to the magnetic field if the inner core were lopsided. They found that the axis of the magnetic field in the model shifted to the side that was growing, which led them to speculate that this change in the axis in the inner core may cause irregular convection patterns in the outer core, which could be responsible for reversals in the magnetic field. They also thought that the position of the axis in the inner core could be the reason why magnetic north is not the same true north – the Magnetic North Pole currently being off the coast of Canada, about 480 km (300 miles) from the Geographic North Pole. If this is correct, then tracing the movement of the Magnetic North Pole over time would give an indication of the way in which the inner core was growing, and perhaps would even show if a reversal in the magnetic field were likely to occur.

Standard
Health, Medical, Research, Science

Brain health linked to how young or old you feel

NEUROSCIENCE STUDY

Besides improving your physical and mental health, feeling younger can also slow down the rate of brain ageing, finds a study.

THE young at heart often insist you are only as old as you feel.

A newly released study has proved they are right, finding that those who feel younger than they are show fewer signs of brain ageing.

Neuroscientists who gave a group of people aged 59 to 84 MRI scans found that those who said they felt younger had more grey matter in their brains and did better in memory tests.

The researchers suggested that those who feel their age or older have picked up on small cognitive changes in their brain, such as mild memory loss. The study, carried out by the University of Seoul in South Korea, is the first to link how old people feel with the physical signs of brain ageing.

Co-author Dr Jeanyung Chey said: “We found people who feel younger have the structural characteristics of a younger brain.

“Importantly, this difference remains robust even when other possible factors – including personality, subjective health, depressive symptoms or cognitive functions – are accounted for. If somebody feels older than their age, it could be a sign for them to evaluate their lifestyle, habits and activities that could contribute to brain ageing and take measures to better care for their brain health.”

The researchers asked 68 healthy people whether they felt older or younger than they were, or whether they felt their age. When their brains were scanned, those who felt younger had more grey matter in key regions such as the hippocampus which is linked to memory.

The scans showed their brains had actually aged less than those of people who felt older, as grey matter tends to decline with age.

The youthful-feeling group also did better in memory tests, including tasks such as recalling details from a story 15 to 30 minutes after hearing it. The researchers suggested that those who feel older may be able to sense the ageing process in their brain as their loss of grey matter may make cognitive tasks more challenging.

Another possibility is that those who feel younger are more likely to lead a more physically and mentally active life, which could cause improvements in brain health. Previous studies have suggested that asking people how old they feel can predict if they will develop dementia, become frail or be taken to hospital. Those who feel older than their age are also more likely to be overweight and suffer illnesses associated with being obese.

Dr Chey, whose study was first published in the journal Frontiers in Aging Neuroscience, said: “Why do some people feel younger or older than their real age?

“Some possibilities include depressive states, personality differences or physical health.

“However, no one had investigated brain ageing processes as a possible reason for differences in subjective age.”

The results suggest that feeling older than one’s age may reflect relatively faster ageing brain structures. Those who feel younger have better-preserved and healthier brain structures.

Some of the biggest changes in grey matter based on age perception were found in the inferior pre-frontal cortex, which helps in suppressing irrelevant information. Loss in this region could cause age-related problems in tasks requiring focus and concentration.

Standard