Our home Earth is an extraordinary planet. The diversity and abundance of life is breathtaking.
About 4.5 billion years ago a planet roughly the size of Mars collided with Earth. Seventy percent of Earth's crust was thrown into outer-space, eventually coalescing to form the Moon.
The remaining 30 percent of the original crust and its continental plates were able to move more easily. This played a crucial role in the process of evolution.
In addition, that collision knocked the Earth's perpendicular axis onto a tilt that is roughly 23 degrees. This created varying day lengths and restricted the freezer-effect of the higher latitudes to the poles. It also enabled wet and dry seasons and lessened the extent of the world's deserts. The tilt is responsible for the mass seasonal animal migrations.
Earth's distance of 93 million miles from the sun appears to be the optimal distance to support life.
Ninety percent of the world's fresh water takes place from evaporation off the ocean - the majority of that occurs around the equator in warm tropical oceans. The remaining 10 percent comes from lakes, rivers and water released by plants.
The location of mountains has a profound effect on where that ocean moisture falls.
Tropical rainforests occupy only three percent of Earth's land mass yet they brim with astounding diversity. Two hundred different species of trees live in a hectare of the Amazon.
The Amazon River carries almost one-fifth of the world's flowing freshwater - equal to that of the next 10 biggest rivers combined. It has over 3,300 fish species - more than the entire Atlantic.
The most common pollinators in the Amazon are bees. Orchid bees travel up to 12 miles each day, searching for food, collecting and pollinating.
Moving north or south of the equator, the zones of subtropical grasslands are bathed in warm sun but the amount of moisture is significantly reduced. There are distinct wet and dry seasons. Grasses - the most widespread land-plant, replace trees.
Grasslands or savannahs support an amazing high number of large animals. These are some of the most efficient ecosystems on the planet.
Grasslands range from Africa to the high steppes of the Tibetan plateau to the tall-grass pampas of South America to the prairies of North America to the frozen tundra in the Arctic.
They support 1.5 million wildebeests along East Africa's Serengeti, 2 million gazelles on Mongolia's steppes and almost 3 million caribou in North America's tundra. They feed thousands of predators like lions, hyenas, wolves and eagles.
Sandwiched between the tropics of Cancer and Capricorn lie Earth's deserts. From outer-space, astronauts can clearly see the dark red colors of Australia's Great Sandy Desert and the remarkable different patterns of the giant Namib sand dunes.
Deserts cover about 19.3 million square miles - over one third of Earth's land mass and they are growing.
About halfway between the tropics and poles are the temperate forests of oaks, beeches, maples, birch and aspens. Broad leaves are very efficient at trapping sunlight, but not tolerant of freezing. So these forests are deciduous and display brilliant leaf colors in the fall.
From northern California to Alaska the world's largest temperate rainforests are conifers. The tallest trees on the face of the Earth are redwoods. Cathedral-like Sitka spruce, western hemlocks, western redcedars and Douglas-firs thrive in lush rainforests with hundreds of millions of salmon, eagles, wolves, black bears and giant grizzlies.
Valdivian coastal rainforests of Chile and Argentina are home to the second largest temperate rainforests. There the alerce or Patagonia cypress can live for over 3,500 years. Monkey-puzzle trees thrive high in the Chilean Andes virtually unchanged since they evolved a couple hundred million years ago.
The largest contiguous forests are the boreal or taiga - Earth's emerald crown. One third of all the trees in the world are found here. European aspen is the most widespread tree on the globe and deciduous Siberian larch can withstand minus 65 Fahrenheit.
Earth's two poles are deep freezers. The Antarctic has an average elevation of 7,590 feet with an average winter temperature of minus 65 Fahrenheit. Only lichens and two flowering plants live there. The emperor penguin is the only animal that stays throughout the winter.
The Arctic is a low-lying basin of frozen sea ice, in the winter it is covered by 5 million square miles of ice. It is home to 40 different species of mammals and 90 flowering plants.
Planet Earth is awesome.
Dr Reese Halter is a Science Communicator: Voice for Ecology, conservation biologist at Cal Lutheran University and public speaker. Contact him through http://DrReese.com
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