Used with permission of the National Media Museum

A study published this week in the journal Nature brings into question the prevailing wisdom about how a country’s development impacts its population growth. Previously, social scientists thought that indicators such as health, standard of living and human capital, collectively called the Human Development Index, could reliably predict negative population growth.

In the past, data showed that wealthier, better educated and healthier countries had lower  fertility rates. This rate is defined as the total number of children the average woman bears through her reproductive years. For example, the US has a Development Index of about 0.9 (one being the highest) and an fertility rate of about 2 children per woman. This is the magic number where  the man and woman who conceived the child are replaced. Whereas for Niger, an undeveloped African country with a Development Index of about 0.3, the fertility rate is 7 children per woman. This means that the average Nigerian couple replace themselves more than 3 times over!

However, the study authors found that once a country’s Development Index surpassed 0.9, that the fertility rate begins to increase. For example,  the US fertility rate is 0.25 higher than it was in 1976 . This increase is true for over 20 other well-developed countries that have passed the 0.9 mark.  For countries currently experiencing population decline this may be of some comfort, as a decline is associated with deflation and the collapse of social welfare systems.

For more on this study, check out Andy Revkin’s New York Times blog post which explores some of the environmental implications  in regards to world population growth. In addition, here is a neat Java Script application developed by Loren Cobb of the University of Colorado, which helps visualize population growth based on different parameters–like fertility rates.

TRANSCRIPT:

Only a subway ride away from Manhattan, Jamaica Bay Wildlife Refuge is located on a sandy atoll in the middle of Jamaica Bay, Queens. It is a small sanctuary for both aquatic birds and turtles.

As you cross over a bridge on the way to the sanctuary, you get the feeling that the subway has magically transformed itself into a boat. The water sits only a few feet below the bottom of the train.

Although technically still in New York City limits, the train drops you in a neighborhood that evokes the feeling of a small beach town. The streets are packed tightly with small, simply-constructed houses.

The first sign that you are near a refuge are the broken clam shells that litter the nearby parking lots. Seagulls drop the shells from on-high, seeking to extract the sweet clam meat from inside.

A newly renovated nature center, operated by the National Park Service greets you at the entrance to a two-mile long trail.

The trail circles around a giant brackish pond that is the home to hundreds of seabirds including swans, Canadian geese, snow geese, seagulls, egrets and various kinds of ducks.

Songbirds find refuge here as well. Take a moment to listen.

Nesting Canadian geese step out to greet you but hiss a warning that you’d better stand back–this is their turf.

Divided from the trail by tall thickets of vines and bushes, a sandy shell-strewn beach beckons for hot and weary feet.

However, this beach is off limits. It’s used as a breeding ground for the endangered diamond-back terrapin turtle.

In this dry environment, succulent plants and even small cactuses  emerge from the sandy soil.

Vegetation on other parts of this little atoll can be dense, as the plants fight for the precious rays of the sun.

The vines of the invasive Oriental Bittersweet (Celastrus orbiculatus) don’t fight fair. They strangle the other plants in their skyward quest.

In the middle of a flat, marshy, expanse full of debris, park service employs have constructed a nesting platform for ospreys–also known as seahawks.

If you look closely, you can just barely make out something stirring in the nest.

I just posted an article and multimedia extravaganza to Scienceline, the webmagazine published by the students of the SHERP program. If I was trying to learn one thing from my time at SHERP, it’s how to put together a print and multimedia package like this.  Check it out!

That’s why I’m always on the look out for micro-level technology that could potentially enable the average Joe (or Jane) to actually generate clean energy.

Two new developments in micro-level energy production showed up on the web this past week that look promising. The first, reported on the website Planetsave, is about a regional energy company that is exploring the economics of turning residential rooftop space into energy-producing solar cell arrays. The twist is that the company would rent the space from homeowners and the wattage generated would feed back into the energy grid rather than to the house where it was generated.  The company, Duke Energy of North Carolina, thinks that this approach may be more economical than building new coal-fired power plants.

The second development is a nearly silent wind turbine for the home, called the Energy Ball, produced by Swedish company HomeEnergy. The turbine is unique (maybe not?) in that it uses a physics principle known as the Venturi Effect to increase its efficiency. (The Venturi effect is basically the observation that a fluid or gas pushed through a long, thin tube moves faster than through a short, fat one.)  Apparently, you can plug this thing right into any free outlet in your house.  Unfortunately, you aren’t going to find these in the clearance rack at IKEA–entry level models start at $4,600.

Solar cells and wind turbines are all good and great for homeowners, but what about us apartment dwellers? Stay tuned.