Facts of Life
Here's a few interesting facts from "Life Counts: Cataloguing Life on Earth":
For every human, there are approximately 500 trees (each, on average, produce three million liters of Oxygen per year). For each human there are 50 birds and 1,000,000,000,000,000,000,000 bacteria (one sextillion). However:
For every elephant, there are 10,000 humans
For every lion, 100,000 humans
Panda, 5,000,000 humans
Sumatran rhinoceros, 100,000,000 (although the pregnant one at the Cincinnati zoo may affect this)
Spix's macaw, over 6 billion (only one is known to exist)
By estimating that modern humans arose 50,000 years ago and applying the best estimates of population over the years, the authors figure that 106,147,380,169 people have been born (as of 2000). Approximately six percent are still living. I've read estimates ranging from 80 billion to 120 billion but never one so exact. (If you've ever heard that "Because of the population explosion, more people are alive today than have died," keep in mind it's a blatant lie.)
The biomass of earth rounds out to approximately 1,850 million tons (British system) of which only 2.3 million tons are animals. In Brussels, plants make up 91.5% of the biomass, humans 7.16, earthworms 0.97%, dogs 0.12%, and cats 0.09%.
In England, there are 75 million field voles (population declining), 59 million humans, nearly 42 million common shrews, 38 million wood mice, 37.5 million rabbits (population rising), and 31 million moles.
What animal is most commonly kept by humans?
Bees - over three trillion
Chickens - nearly 13.5 billion
Cattle - nearly 1.5 billion
Sheep - over one billion
Pigs - nearly one billion
Strangely enough, people keep over 2.6 million "farm" crocodiles
In just the U.S. and Europe people keep 106 million cats and 94 million dogs (but more people own dogs than cats). More people own fish than dogs and cats combined.