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.
Arthritis patients could one day benefit from a novel form of medicine, according to researchers at Queen Mary University of London (QMUL). Their early study indicates that arthritic cartilage, previously thought to be impenetrable to therapies, could be treated by a patient’s own ‘microvesicles’ that are able to travel into cartilage cells and deliver therapeutic agents.
Microvesicles are very small subcellular structures (0.05 to 1 micrometer in diameter) that consist of fluid enclosed by a membrane. They are released by cells in copious numbers to transfer lipids and proteins to target cells, yet their role in disease has been poorly understood.
Some white blood cells’ microvesicles tend to accumulate in large numbers in the joints of rheumatoid arthritis patients. The biological impact of these microvesicles has been intriguing to researchers, because they are known to contain over 300 types of protein that vary in different situations.
Lead author Professor Mauro Perretti from QMUL’s William Harvey Research Institute said: “Cartilage has long been thought to be impenetrable to cells and other small structures, leading to strong limitations in our abilities to deliver therapies for arthritis. To our surprise, we’ve now discovered that vesicles released from white blood cells can ‘travel’ into the cartilage and deliver their cargo, and that they also have a protective effect on cartilage affected by arthritis.
“Our study indicates that these vesicles could be a novel form of therapeutic strategy for patients suffering from cartilage damage due to a range of diseases, including osteoarthritis, rheumatoid arthritis and trauma. Treating patients with their own vesicles may only require a day in hospital, and the vesicles could even be ‘fortified’ with other therapeutic agents, for example, omega-3 fatty acids or other small molecules.”
The study, published in Science Translational Medicine and funded by Arthritis Research UK, the Nuffield Foundation (Oliver Bird Fund) and the Wellcome Trust, examined the role of microvesicles in mice models and human cartilage cells, investigating their effect on experimental arthritic disease.
Mice were genetically modified to have reduced vesicle production. These mice exhibited cartilage damage from inflammatory arthritis, but showed reduced cartilage degradation when treated with microvesicles. The microvesicles were also found to lead to cartilage protection when repeated in human cells.
The researchers additionally found that one particular cellular receptor, known as ‘FPR2/ALX’, played a role in protecting cartilage tissue and could therefore be targeted by new small molecules for the treatment of cartilage erosive diseases.
Arthritis Research UK’s Medical Director, Stephen Simpson said: “By using the body’s own transport system to get new and current therapeutic agents directly into the cartilage, holds the promise that we will be able to reduce joint damage more effectively than ever. A healthy and intact joint results in less pain and disability improving the quality of life of millions of people living with arthritis in the UK.”
The authors say that these early results reveal a possible new therapeutic approach for treating damaged cartilage of arthritic joints. Further studies in humans will be needed to confirm the therapeutic potential of the new approach.
As the American media continues to buzz over who is more or less likely to secure the Republican and Democratic nominations for U.S. President, researchers in the journal Trends in Ecology & Evolution review some interesting perspectives on the nature of leadership. The experts from a wide range of disciplines examined patterns of leadership in a set of small-scale mammalian societies, including humans and other social mammals such as elephants and meerkats.
“While previous work has typically started with the premise that leadership is somehow intrinsically different or more complex in humans than in other mammals, we started without a perceived notion about whether this should be the case,” said Jennifer Smith of Mills College in Oakland, California. “By approaching this problem with an open mind and by developing comparable measures to compare vastly different societies, we revealed more similarities than previously appreciated between leadership in humans and non-humans.”
Chimpanzees travel together, capuchins cooperate in fights, and spotted hyenas cooperate in hunting, but the common ways that leaders promote those collective actions has remained mysterious, Smith and her colleagues say. It wasn’t clear just how much human leaders living in small-scale societies have in common with those in other mammalian societies either.
To consider this issue, a group of biologists, anthropologists, mathematicians, and psychologists gathered at the National Institute for Mathematical and Biological Synthesis. These experts reviewed the evidence for leadership in four domains–movement, food acquisition, within-group conflict mediation, and between-group interactions–to categorize patterns of leadership in five dimensions: distribution across individuals, emergence (achieved versus inherited), power, relative payoff to leadership, and generality across domains.
Despite what those ongoing presidential primaries might lead one to think, the analysis by the scientific experts finds that leadership is generally achieved as individuals gain experience, in both humans and non-humans. There are notable exceptions to this rule: leadership is inherited rather than gained through experience among spotted hyenas and the Nootka, a Native Canadian tribe on the northwest coast of North America.
In comparison to other mammal species, human leaders aren’t so powerful after all. Leadership amongst other mammalian species tends to be more concentrated, with leaders that wield more power over the group.
Smith says the similarities probably reflect shared cognitive mechanisms governing dominance and subordination, alliance formation, and decision-making–humans are mammals after all. The differences may be explained in part by humans’ tendency to take on more specialized roles within society.
“Even in the least complex human societies, the scale of collective action is greater and presumably more critical for survival and reproduction than in most other mammalian societies,” Smith said.
The researchers now plan to further quantify the various dimensions identified in the new work. There’s still plenty more to learn. “As ambitious as our task was, we have only just scraped the surface in characterizing leadership across mammalian societies and some of the most exciting aspects of the project are still yet to come as biologists and anthropologists implement our novel scheme for additional taxa and societies,” Smith said.
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