Does the Amazon Rainforest Really Produce 20 Percent of the World's Oxygen?

SL_Photography/iStock via Getty Images
SL_Photography/iStock via Getty Images

Richard Muller:

No. In fact, under normal conditions (prior to human-caused fires) the Amazon [rain]forest is in a steady state. Oxygen is produced by photosynthesis and consumed by decay. If these were out of balance, then the mass of wood in the Amazon must change.

That means if the Amazon were to disappear today, instantly (e.g. we harvested all the wood and used it to build houses) then the oxygen and carbon dioxide in the atmosphere would continue on at the same level. Until, that is, the wood rots. Then the carbon dioxide levels would increase.

Except for the biomass decrease from human-caused fires, the biomass of the Amazon has not been changing. That means that no net carbon dioxide is being removed from the atmosphere, so no net oxygen is being released from carbon dioxide.

Recently the Amazon biomass has been changing due to fires. When that happens, the wood and other carbohydrates in the trees combine with oxygen and produce CO2 and H2O. Thus the burning of the rainforests contributes to global warming.

But under normal situations, when the biomass of the Amazon is not changing, there is no net production of oxygen or carbon dioxide.

Incidentally, many writers who don’t understand this—and mistakenly think that the Amazon produces net oxygen—double their error by using a backward metaphor. They refer to the Amazon basin the "lungs of the world," but lungs are the organ that remove oxygen from the air and replace it with carbon dioxide, not the other way around.

Where did the 20 percent figure come from? The best guess is that ecologists have calculated that 20 percent of the photosynthesis of the world takes place in the Amazon basin. But so does 20 percent of the consumption.

This post originally appeared on Quora. Click here to view.

What's the Difference Between Yams and Sweet Potatoes?

Julia_Sudnitskaya/iStock via Getty Images
Julia_Sudnitskaya/iStock via Getty Images

This Thanksgiving, families across the country will enjoy a traditional meal of turkey, stuffing, and sweet potatoes ... or are they yams? Discussions on the proper name for the orange starchy stuff on your table can get more heated than arguments about topping them with marshmallows. But there's an easy way to tell the difference between sweet potatoes and yams: If you picked up the tuber from a typical American grocery store, it's probably a sweet potato.

So what's a sweet potato?

Sweet potato and yam aren't just different names for the same thing: The two produce items belong to their own separate botanical categories. Sweet potatoes are members of the morning glory family. Regular potatoes like russets, meanwhile, are considered part of the nightshade family, which means that sweet potatoes aren't actually potatoes at all.

Almost all of the foods most Americans think of as yams are really sweet potatoes. The root vegetable typically has brown or reddish skin with a starchy inside that's orange (though it can also be white or purple). It's sold in most supermarkets in the country and used to make sweet potato fries, sweet potato pie, and the sweet potato casserole you have at Thanksgiving.

Then what's a yam?

Yams.
Yams.
bonchan/iStock via Getty Images

Yams are a different beast altogether. They are more closely related to lilies and grasses and mostly grow in tropical environments. The skin is more rough and bark-like than what you'd see on a sweet potato, and the inside is usually white or yellowish—not orange.

They're a common ingredient in parts of Asia, Africa, and the Caribbean. Because the inside of a yam is less moist than the inside of a sweet potato, they require more fat to make them soft and creamy. They're also less sweet than their orange-hued counterparts. In many regions in the U.S., yams aren't sold outside of international grocery stores.

Where did the mix-up come from?

Also sweet potatoes.
Also sweet potatoes.
Kateryna Bibro/iStock via Getty Images

So if yams and sweet potatoes are two totally different vegetables that don't look or taste that similar, why are their names used interchangeably in the U.S.? You can blame the food industry. For years, "firm" sweet potatoes, which have brown skin and whitish flesh, were the only sweet potatoes grown in the U.S. In the early 20th century, "soft" sweet potatoes, which have reddish skin and deep-orange flesh, entered the scene. Farmers needed a way to distinguish the two varieties, so soft sweet potatoes became yams.

Nearly a century later, the misnomer shows no signs of disappearing. Many American supermarkets still call their orange-fleshed sweet potatoes yams and their white-fleshed ones sweet potatoes, even though both items are sweet potatoes. But this isn't a strict rule, and stores often swap the names and make things even more confusing for shoppers. So the next time you're shopping for a recipe that calls for sweet potatoes, learn to identify them by sight rather than the name on the label.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

What's the Difference Between Memorial Day and Veterans Day?

iStock/flySnow
iStock/flySnow

It may not be easy for some people to admit, but certain national holidays often get a little muddled—namely, Memorial Day and Veterans Day. In fact, the U.S. Department of Veterans Affairs sees the confusion often enough that they spelled out the distinction on their website. The two days are held six months apart: Veterans Day is celebrated every November 11, and Memorial Day takes place on the last Monday of May as part of a three-day weekend with parades and plenty of retail sales promotions. You probably realize both are intended to acknowledge the contributions of those who have served in the United States military, but you may not recall the important distinction between the two. So what's the difference?

Veterans Day was originally known as Armistice Day. It was first observed on November 11, 1919, the one-year anniversary of the end of World War I. Congress passed a resolution making it an annual observance in 1926. It became a national holiday in 1938. In 1954, President Dwight D. Eisenhower changed the name from Armistice Day to Veterans Day to recognize veterans of the two world wars. The intention is to celebrate all military veterans, living or dead, who have served the country, with an emphasis on thanking those in our lives who have spent time in uniform.

We also celebrate military veterans on Memorial Day, but the mood is more somber. The occasion is reserved for those who died while serving their country. The day was first observed in the wake of the Civil War, where local communities organized tributes around the grave sites of fallen soldiers. The observation was originally called Decoration Day because the graves were adorned with flowers. It was held May 30 because that date wasn't the anniversary for any battle in particular and all soldiers could be honored. (The date was recognized by northern states, with southern states choosing different days.) After World War I, the day shifted from remembering the fallen in the Civil War to those who had perished in all of America's conflicts. It gradually became known as Memorial Day and was declared a federal holiday and moved to the last Monday in May to organize a three-day weekend beginning in 1971.

The easiest way to think of the two holidays is to consider Veterans Day a time to shake the hand of a veteran who stood up for our freedoms. Memorial Day is a time to remember and honor those who are no longer around to receive your gratitude personally.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

SECTIONS

arrow
LIVE SMARTER