But, according to a team of environmentalists led by Linus Blomqvist of The Breakthrough Institute, that ubiquitous, guilt inducing statistic is oversimplified and very likely wrong. Blomqvist and his coauthors detail their arguments in Tuesday's release of PLoS Biology.
"Ecological footprint measurements, as currently constructed and presented, are so misleading as to preclude their use in any serious science or policy context," he says.
Blomqvist, a dedicated, yet pragmatic conservationist, recognizes that any overarching global environmental metric won't be perfect. The Global Footprint Network (GFN) originally devised the ecological footprint metric decades ago. The overall value is derived from gauging the ecological supply and demand of six different components: cropland, grazing land, forest, fishing ground, built-up land, and carbon footprint. Everything makes sense at first glance, but delve a little deeper and problems with their methods and the resulting "1.5 Earths" statistic become apparent.
According to GFN's own data, every single component is either very close to in balance or is in surplus, except one: carbon footprint. That category alone is responsible for the deficit that gives rise to the idea that we're using 1.5 Earths.
"Indeed, if one excludes carbon, global biocapacity exceeds the footprint of consumption by about 45% in 2008," Blomqvist says.Blomqvist doesn't question that we're putting too much carbon into the atmosphere, but he does question whether or not the amount is equal -- as the graph points out -- to .85 Earths.
To calculate carbon footprint, GFN simply defines carbon uptake by forests as the single method to offset human greenhouse gas emissions. This makes the carbon uptake rate extremely significant -- a tiny change can drastically alter the resulting footprint. The GFN currently estimates the rate to be 0.97 metric tons of carbon per hectare of forest per year, meaning that we'd have to plant dense forests on over half of Earth's land to bring our ecological footprint into balance. But in fact, forests' global carbon uptake rate fluctuates each year, from as low as zero to as high as 6. If the value was simply altered to 2.6 -- which is plausible -- then the carbon deficit disappears.
Blomqvist and his team also take aim at other weaknesses of the "1.5 Earths" calculation. For example, the way the cropland and grazing land categories are formulated, they can never be in deficit. Humans decide how much land to use for agriculture, and we can't technically use more than we create. Moreover, the GFN doesn't even register declines in global forest area for their footprint calculation. If these shortcomings were corrected, our global footprint would very likely increase.
William Rees and Mathis Wackernagel, the scientists who originally created the ecological footprint statistic, disagree with many of Blomqvist's assertions. They contend that their calculations are best put to use on a local or national scale, not a global one.
"There is nothing gained by not knowing one's country's biocapacity balance," Rees and Wackernagel counter, "and there are presently no better estimates."
Furthermore, they stand by their estimate of real-world forests' carbon uptake rate, arguing that the rate is obviously insufficient to prevent potentially catastrophic warming.
"The carbon sequestration rate is not 2.6 or no carbon dioxide would be accumulating in the atmosphere," they say.
Blomqvist and his colleagues offer recommendations for improving any sort of ecological measurement. Chiefly, it should take into account declining stocks of natural resources, include estimates of uncertainty, and illuminate diverse pathways to achieving sustainability. Planting trees, while worthwhile, is definitely not the only option to "using" one Earth instead of 1.5.
(Image: Drawn Earth via Shutterstock)
Source: Blomqvist L, Brook BW, Ellis EC, Kareiva PM, Nordhaus T, et al. (2013) Does the Shoe Fit? Real versus Imagined Ecological Footprints. PLoS Biology 11(11): e1001700. doi:10.1371/journal.pbio.1001700
Source: Rees WE, Wackernagel M (2013) The Shoe Fits, but the Footprint is Larger than Earth. PLoS Biology 11(11): e1001701. doi:10.1371/journal.pbio.1001701
This evening, city blocks across the country will be packed with people masquerading as ghouls, goblins, specters, and (God forbid) twerking Miley Cyruses, all tricking, treating, and occasionally extorting their ways to a bounty of delectable candy. When bags are teeming and parents are seething, that's when the wanton gluttony can finally begin.
The key to chocolate's deadliness is a bitter-tasting chemical called theobromine. Like nicotine, cocaine, and morphine, theobromine is an alkaloid, defined chiefly by the presence of at least one nitrogen compound in a heterocyclic ring. Cacao beans, from which chocolate is derived, naturally contain approximately 1.2% of the compound by weight, and since all chocolate has some amount of cacao, the popular sweet also has a little theobromine.
To develop nausea from theobromine intoxication requires piggishness on the order of Augustus Gloop from Willy Wonka and the Chocolate Factory -- you have to eat a lot. To die from it is a chore on a whole other magnitude. The dose at which 50% of people will expire from theobromine intake is around 1000 milligrams per kilogram of body weight. That means that an average ten-year-old child stuffing sweets into his or her mouth this evening would need to consume 1,900 Hersey's milk chocolate miniature candies. If they have a taste for dark chocolate -- which contains more cacao, and thus, theobromine -- they'd still have to devour 659 of those miniature candies, 16.3 pounds of chocolate!
What about freon? Well, it was the first chlorofluorocarbon (CFC) ever invented. Scientists were startled in 1985 to discover a large hole in Earth's protective ozone layer -- which shields us from damaging ultraviolet light -- over Antarctica. They quickly found out that CFCs like freon were the culprits. The discovery catalyzed a major international agreement in 1988, where over 180 countries agreed to substantially reduce or phase out entirely the production of CFCs. 
It was in these ambiguous gender situations that -- for many years -- rigid cultural stereotypes of sexuality seeped into the hospital. Birth certificates demanded a "male" or "female" classification, and doctors desired to deliver. Thus, when a newborn's sex was unclear, physicians would perform gender reassignment surgery. For boys with penises smaller than one-inch when stretched, this meant getting turned into girls. They would be castrated, and have a "vagina" fashioned out of extra skin or colon. On the other hand, girls born with large clitorises would have them trimmed to a less prominent size. In these situations, surgeries were often conducted hastily, with little time for parents to consider the ramifications of such a decision. Needless to say, the young individuals being operated on were never consulted. Moreover, the procedures weren't without physical repercussions. Often, they would render the baby infertile and severely limit sensations of sexual pleasure.
The mechanisms behind copper's antimicrobial powers are manifold. When absorbed, copper mucks with a great many biological processes. In cells, elevated copper levels cause damaging or even deadly levels of hydrogen peroxide to accrue. Excess copper atoms, loitering about, can also turn vagrant and create other problems. Like misguided youths looking for love in the all the wrong places, they bind to proteins that don't require copper to function. The "inappropriate" pairing leaves the protein inoperable, or literally in shambles. Most disturbingly (to microbes, at least) too much copper can weaken the cell membrane, resulting in the slow leakage of essential nutrients. Eventually, the cell dies. 
Rain rarely falls in Goldfields-Esperance, which sports average summer temperatures around 93 degrees Fahrenheit. So the hearty, but thirsty eucalyptus trees extend their roots far underground in search of water, sometimes as deep as 40 meters! Along the way, the roots run through gold-enriched earth, drinking in both moisture and metal. Carried by water, the gold flows through the trees' vascular systems and gets deposited within the cells, themselves. The researchers found leaves and twigs to contain particularly high concentrations of gold: 80 and 44 parts per billion, respectively. That's not enough to make the tree shimmer and sparkle in the midday sun, or even to make a gold ring -- one would have to cut down 500 of the trees just to extract enough metal. But it's still a lot in a biological sense.*
Hambleton is absolutely correct. Chiropractors claim that their manipulations can cure conditions ranging from infant colic, to ear infections, to bed-wetting. But research conducted in respected, science-based medical journals shows otherwise. (See: colic, asthma, ear infection.) 
3. Elephant Trunks actually have "fingers." African elephants have two while Asian elephants only have one. That's why the former is able to grasp objects by pinching the opposing tips of the trunk while the latter must wrap its trunk round objects like a boa constrictor.
4. The elephant's trunk contains over 40,000 muscles, divided into as many as 150,000 individual units! Compare that to the human body, which contains a paltry 639 muscles, and you start to get an idea how intricate the appendage is.
