Is There More Hair or Grass in the World?

This is an interesting question that doesn’t have a definitive scientific answer yet. At first glance, most people would probably guess that there is more grass than human hair on earth. However, when you start to dig into the details, it becomes a surprisingly complex question with arguments on both sides. Here is an overview of the key considerations in determining whether there is more grass or human hair on earth.

Why You Might Think Grass is More Abundant

Grass is practically everywhere and covers massive areas of land across the globe. Savannas, prairies, steppes, and tundra ecosystems are dominated by grasses. Even in forests and deserts, grass is abundant on the ground layer. Grasslands and pastures used for agriculture take up vast areas.

In comparison, human hair is obviously concentrated on people’s heads and bodies. With an estimated global population of 7.7 billion, there are certainly a lot of humans, but we still take up a tiny fraction of the earth’s surface relative to the massive grassy areas. Our intuition says that grass must dominate in terms of sheer area covered and number of individual blades.

Estimating the Abundance of Human Hair

However, the number of strands of human hair may be more vast than you’d expect. Let’s consider some estimates:

• The average human head has about 100000 to 150,000 hairs.

• Multiply this by the global population of 7.7 billion, and you get an estimated 770 trillion to 1,155 trillion hairs just from human heads alone.

• The human body has hair on more than just the scalp. A 2016 study estimated the average human has 5 million hairs covering their body.

• If each person has around 5 million hairs, the global human population has around 38.5 quintillion hairs on bodies.

When you add up head and body hair, the total number of human hairs in the world could be upwards of 39.5 quintillion. That’s clearly a massive number, even compared to the seeming infinitude of grass blades across the globe.

Estimating Grass Abundance is Complex

Estimating the total number of grass blades on earth is surprisingly difficult There have been a few different attempts

• One estimate suggested there are about 3.04 × 10^18 blades of grass, which is 304 quintillion.

• A Quora user named Progardenman calculated there are about 29 × 10^29 blades of grass globally, which equals 29 decillion.

• Others have proposed figures from 25 to 50 quintillion blades of grass worldwide.

As you can see, the estimates vary widely. Unlike the relatively straightforward calculation of human hairs, grass abundance over the entire earth is hard to pin down. The number likely falls somewhere between 25 quintillion to 29 decillion blades.

Comparing Grass and Hair Estimates

Based on the above calculations, human hair seems like it could plausibly exceed the number of grass blades globally. However, the estimates are uncertain enough that it’s hard to make a definitive claim either way.

If we take the estimate of 39.5 quintillion hairs on human bodies worldwide, it exceeds the low end estimate of grass abundance at 25 quintillion blades but falls far short of the high end estimate of 29 decillion blades. More rigorous scientific sampling would be needed to improve the accuracy of these global estimates.

In the end, while human intuition favors grass dominating in terms of sheer numbers, the reality is the abundances of grass and human hair worldwide are much closer than you might expect. The massive global human population makes our combined hair quite abundant. The jury is still out, but human hair very well could add up to more than grass globally. But more research is needed to answer this hairy question definitively.

Other Factors to Consider

Beyond just total numbers, there are a few other considerations that complicate the hair vs. grass debate:

• Variation in hair and grass density: Hair density varies dramatically by body part and between people. Grass density fluctuates across climates and environments. More sampling would be needed to accurately quantify densities.

• Grass growth rates: Grass grows rapidly so blades die frequently; new shoots continually replace them. The actual number of grass blades at any given time is fluctuating.

• Hair length: Grass blades are small, usually just centimeters long. Scalp hairs can grow over a meter long. So human hairs likely take up more physical volume.

• Defining “hair”: Does animal fur count as hair in this comparison? Do grass-like plants such as cereals and bamboos count as grass? The definitions matter.

• Changing abundances: Humans are increasing in population while habitat loss may be reducing grasslands. Abundances are moving targets.

Given these complexities, the “more hair vs. grass” question does not have an easy or definitive answer right now. But it’s an interesting thought experiment from an ecological perspective and shows how a simple question can quickly get complicated when you dig into the details. The true global abundances of these organisms remain elusive for now. More rigorous sampling and density estimates would be needed to conclusively resolve this hairy debate.

The Importance of Grass and Hair

Beyond just the abundance, it’s worth considering the important ecological roles of grass and human hair:

The Significance of Grass

• Grasses are vital primary producers forming the base of many food webs. Numerous species rely on grasses for food and shelter.

• Grasslands sequester carbon, preventing it from entering the atmosphere as CO2. They offer huge ecological services.

• Grasses prevent soil erosion and desertification by securing topsoil with their dense root systems. Their extensive underground biomass also stores carbon.

• Grasses support livestock that provide meat, dairy and materials to humans around the world.

The Significance of Human Hair

• Head hair protects the scalp from UV radiation and cold temperatures. It enhances sensation and keeps dust from eyes and nose.

• Body hair retains pheromones for sexual signaling. It also aids movement of sebaceous secretions.

• Scalp hair is important for self-expression, identity and cultural practices (e.g. Hairstyles). It influences attractiveness and mate selection.

• Human hair supports a multi-billion dollar global industry including hair care products, wigs, extensions, transplants, etc. It drives research and development.

So while the global abundances of grass and human hair are still up for debate, it’s clear both play important roles on earth in their own ways. Quantifying and comparing their abundances also reveals how a simple question can lead to complex ecological analyses. Even if we can’t definitively answer whether there is more hair or grass in the world yet, exploring this question is an interesting thought experiment that gives insight into the immensity and interconnectedness of life on our planet.