|Planet Earth was formed about 4.54 billion years ago according
to evidence from radiometric dating. Within Earth's first billion years
life appeared in its oceans and began to affect the atmosphere and surface
promoting proliferation of aerobic as well as anaerobic organisms, over
time causing formation of the atmosphere's ozone layer. This layer and the
geomagnetic field blocked the most life-threatening parts of the Sun's radiation,
so life was able to flourish on land as well as in water.
Since then the combination of Earth's distance from the Sun, its physical properties and its geological history have allowed life to thrive and evolve.Earth is the third planet from our Sun, the densest planet in the Solar System, and the only astronomical object known—so far—to support life. The earliest life on Earth arose at least 3.5 billion years ago and Earth's biodiversity has expanded continually except when interrupted by mass extinctions. Earth is currently home to 10–14 million species of life, of which about 1.2 million have been documented. More than 7.3 billion humans depend upon its biosphere and minerals to survive.
Life on Earth evolved to survive and thrive within the constraints of its delicate, thin, biosphere. The chemistry of our air allows aerobic organisms to breathe and live. Radiation from the Sun supports photosynthesis for plants to grow and feed us. Both air and water temperatures are rising. The balance between just enough radiation and too much is determined by the composition of our thin atmosphere (ozone level). Humans have altered the natural values by using fossil fuels and coal for energy. Carbon dioxide levels are rising; recently recorded as >400ppm the highest during human history. Plants that fix (absorb) CO2 are in decline in part due to clear-cutting of tropical rainforests for agriculture. The oceans now must absorb more CO2 to compensate, and this leads to acidification and loss of PH sensitive species. Ocean temperature rise also contributes to hypoxic (low oxygen) conditions. The human population on Earth is growing at a rate our resources can't sustain.
There have been 5 mass extinctions; Earth survived; new life developed and slowly adapted to changes each time.
The problem we now face is about timing: compensatory evolutionary changes for current life forms cannot happen as quickly as we degrade the environment. Life on Earth developed over millions of years, yet the damage we've done occurred in a few hundred. The scientific community understands what's happening and how to fix it, yet short-sighted economic imperatives discourage change.
We must make positive changes now. Every day we have choices that make a difference. We can both support and protest with our 'wallet'. My goal is to increase awareness about these issues and choices.
|Good planets are hard to find so let's take care of this one|
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