There is no longer any doubt: We are entering a mass extinction that threatens humanity’s existence.
That is the bad news at the center of a new study by a group of scientists including Paul Ehrlich, the Bing Professor of Population Studies in biology and a senior fellow at the Stanford Woods Institute for the Environment. Ehrlich and his co-authors call for fast action to conserve threatened species, populations and habitat, but warn that the window of opportunity is rapidly closing.
“[The study] shows without any significant doubt that we are now entering the sixth great mass extinction event,” Ehrlich said.
Although most well known for his positions on human population, Ehrlich has done extensive work on extinctions going back to his 1981 book, Extinction: The Causes and Consequences of the Disappearance of Species. He has long tied his work on coevolution, on racial, gender and economic justice, and on nuclear winter with the issue of wildlife populations and species loss. Read more »
The world’s population will increase from today’s 7.3 billion people to 9.7 billion in 2050 and 11.2 billion at century’s end, John R. Wilmoth, the director of the United Nations (UN) Population Division, told a session focused on demographic forecasting at the 2015 Joint Statistical Meetings (JSM 2015) today in Seattle.
The UN projection suggests there will not be an end to world population growth this century unless there are unprecedented fertility declines in those parts of sub-Saharan Africa that are still experiencing rapid population growth. The UN estimated the probability that world population growth will end within this century to be 23%.
Wilmoth’s presentation–”Populations Projections by the United Nations“–was made as part of an invited session titled “Better Demographic Forecasts, Better Policy Decisions” held here today.
Wilmoth told the audience that according to models of demographic change derived from historical experience, it is estimated the global population will be between 9.5 and 13.3 billion people in 2100. In the United States, the population is projected to add 1.5 million people per year on average until the end of the century, pushing the current count of 322 million people to 450 million, he said.
The primary driver of global population growth is a projected increase in the population of Africa. The continent’s current population of 1.2 billion people is expected to rise to between 3.4 billion and 5.6 billion people by the end of this century. The continent’s population growth is due to persistent high levels of fertility and the recent slowdown in the rate of fertility decline. The total fertility rate (TFR) has been declining in Africa over the past decade, but has been doing so at roughly one-quarter of the rate at which it declined in Asia, Latin America and the Caribbean in the 1970s.
In some African countries, the TFR decline appears to have stalled. For instance, in Nigeria–the continent’s most-populous country–the high fertility rate would result in a more than fourfold projected increase in total population by 2100–from 182 million to 752 million people. Wilmoth said although there is considerable uncertainty about these future trends, there is a 90% chance Nigeria’s population will exceed 439 million people in 2100, which is nearly 2.5 times its current size.
Looking more closely at the global projections, Wilmoth said Asia, with a current population of 4.4 billion, is likely to remain the most populous continent, with its population expected to peak around the middle of the century at 5.3 billion, and then to decline to around 4.9 billion people by the end of the century.
The UN report also examines the level of population aging in different countries, noted Wilmoth. One such measure is the potential support ratio (PSR), which is equal to the number of people aged 20 to 64 divided by the number of people aged 65 or over and is frequently considered the number of workers per retiree. Japan currently has the lowest PSR at 2.1, followed by Italy at 2.6.
In the United States, where the median age of the population is expected to increase from today’s 38.0 years to 44.7 years in 2100, the PSR is projected to decline from 4.0 to 1.9. Other countries that will experience sharp declines in their PSR by the end of the century are the following:
- Germany, current 2.9 to projected 1.4
- China, current 7.1 to projected 1.4
- Mexico, current 8.7 to projected 1.4
- Bangladesh, current 11.2 to 1.6
Only five countries are projected to have a PSR above 5.0 in 2100: Niger, Somalia, Nigeria, Gambia and Angola. Niger is expected to have the highest PSR by the end of the century at 6.5.
These results have important policy implications for national governments. Rapid population growth in high-fertility countries can exacerbate a range of existing problems–environmental (resource scarcity and pollution), health (maternal and child mortality), economic (unemployment, low wages and poverty), governmental (lagging investments in health, education and infrastructure), and social (political unrest and crime), explained Wilmoth.
Developing countries with young populations but lower fertility–such as China, Brazil and India–face the prospect of substantial population aging before the end of the century. The new projection suggests these countries need to invest some of the benefits of their demographic dividend in the coming decades toward provisions for the older population of the future such as social security, pensions and health care.
Cerebral palsy (CP) is the most common cause of physical disability in children. It has historically been considered to be caused by factors such as birth asphyxia, stroke and infections in the developing brain of babies. In a new game-changing Canadian study, a research team from The Hospital for Sick Children (SickKids) and the Research Institute of the McGill University Health Centre (RI-MUHC) has uncovered strong evidence for genetic causes of cerebral palsy that turns experts’ understanding of the condition on its head.
The study, published online August 3 in Nature Communications could have major implications on the future of counselling, prevention and treatment of children with cerebral palsy.
“Our research suggests that there is a much stronger genetic component to cerebral palsy than previously suspected,” says the lead study author Dr. Maryam Oskoui, Paediatric neurologist at The Montreal Children’s Hospital (MCH) of the MUHC, co-director of the Canadian Cerebral Palsy Registry and an Assistant Professor in the Department of Paediatrics and Department of Neurology and Neurosurgery at McGill University. “How these genetic factors interplay with other established risk factors remains to be fully understood. For example, two newborns exposed to the same environmental stressors will often have very different outcomes. Our research suggests that our genes impart resilience, or conversely a susceptibility to injury.”
Children with cerebral palsy have difficulties in their motor development early on, and often have epilepsy and learning, speech, hearing and visual impairments. Two out of every thousand births are affected by cerebral palsy with a very diverse profile; some children are mildly affected while others are unable to walk on their own or communicate. Genetic testing is not routinely done or recommended, and genetic causes are searched for only in rare occasions when other causes cannot be found.
The research team performed genetic testing on 115 children with cerebral palsy and their parents from the Canadian Cerebral Palsy Registry, many of which had other identified risk factors. They found that 10 per cent of these children have copy number variations (CNVs) affecting genes deemed clinically relevant. In the general population such CNVs are found in less than one per cent of people. CNVs are structural alterations to the DNA of a genome that can be present as deletions, additions, or as reorganized parts of the gene that can result in disease.
“When I showed the results to our clinical geneticists, initially they were floored,” says Dr. Stephen Scherer, Principal Investigator of the study and Director of The Centre for Applied Genomics (TCAG) at SickKids. “In light of the findings, we suggest that genomic analyses be integrated into the standard of practice for diagnostic assessment of cerebral palsy.”
The study also demonstrates that there are many different genes involved in cerebral palsy. “It’s a lot like autism, in that many different CNVs affecting different genes are involved which could possibly explain why the clinical presentations of both these conditions are so diverse,” says Scherer, who is also Director of the University of Toronto McLaughlin Centre. “Interestingly, the frequency of de novo, or new, CNVs identified in these patients with cerebral palsy is even more significant than some of the major CNV autism research from the last 10 years. We’ve opened many doors for new research into cerebral palsy.”
“Finding an underlying cause for a child’s disability is an important undertaking in management,” says Dr. Michael Shevell, co-director of the Canadian Cerebral Palsy Registry and Chair of the Department of Paediatrics at the MCH-MUHC. “Parents want to know why their child has particular challenges. Finding a precise reason opens up multiple vistas related to understanding, specific treatment, prevention and rehabilitation. This study will provide the impetus to make genetic testing a standard part of the comprehensive assessment of the child with cerebral palsy.”
Daily marijuana use among the nation’s college students is on the rise, surpassing daily cigarette smoking for the first time in 2014.
A series of national surveys of U.S. college students, as part of the University of Michigan’s Monitoring the Future study, shows that marijuana use has been growing slowly on the nation’s campuses since 2006.
Daily or near-daily marijuana use was reported by 5.9 percent of college students in 2014–the highest rate since 1980, the first year that complete college data were available in the study. This rate of use is up from 3.5 percent in 2007. In other words, one in every 17 college students is smoking marijuana on a daily or near-daily basis, defined as use on 20 or more occasions in the prior 30 days.
Other measures of marijuana use have also shown an increase: The percent using marijuana once or more in the prior 30 days rose from 17 percent in 2006 to 21 percent in 2014. Use in the prior 12 months rose from 30 percent in 2006 to 34 percent in 2014. Both of these measures leveled in 2014.
“It’s clear that for the past seven or eight years there has been an increase in marijuana use among the nation’s college students,” said Lloyd Johnston, the principal investigator of the study. “And this largely parallels an increase we have been seeing among high school seniors.”
Much of this increase may be due to the fact that marijuana use at any level has come to be seen as dangerous by fewer adolescents and young adults. For example, while 55 percent of all 19-to-22-year-old high school graduates saw regular marijuana use as dangerous in 2006, only 35 percent saw it as dangerous by 2014.
The study also found that the proportion of college students using any illicit drug, including marijuana, in the prior 12 months rose from 34 percent in 2006 to 41 percent in 2013 before falling off some to 39 percent in 2014. That seven-year increase was driven primarily by the increase in marijuana use, though marijuana was not the only drug on the rise.
The proportion of college students using any illicit drug other than marijuana in the prior 12 months increased from 15 percent in 2008–the recent low point–to 21 percent in 2014, including a continuing increase in 2014. The increase appears attributable mostly to college students’ increased use of amphetamines (without a doctor’s orders) and use of ecstasy.
These and other results about drug use come from Monitoring the Future, an annual survey that has been reporting on U.S. college students’ substance use of all kinds for 35 years. The study began in 1980 and is conducted by the U-M Institute for Social Research with funding from the National Institute on Drug Abuse, one of the National Institutes of Health.
College students’ nonmedical use of amphetamines in the prior 12 months nearly doubled between 2008 (when 5.7 percent said they used) and 2012 (when 11.1 percent used), before leveling at 10.1 percent in 2014.
“It seems likely that this increase in amphetamine use on the college campus resulted from more students using these drugs to try to improve their studies and test performance,” Johnston said. Read more »
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