Long before the genesis of life, Earth was covered in water.
Today, water vapor fills the atmosphere.
Great masses of ice stretch across the planet’s poles, and beautiful, aquatic landscapes decorate
its many continents.
Our blue planet owes its fruitful development to this clear, inorganic solvent, but how
could a single chemical substance influence the evolution of an entire planet?
Roughly 10% of the world’s land area is covered in glacial ice, a mono-mineralic rock
made of solid H2O.
Masses of glacial ice form ice caps and ice sheets, as well as the largest glaciers on
Earth.
In North America, the largest frozen glacier is the Bering Glacier, which covers approximately
5,000 square kilometers of the Alaskan Peninsula.
Like all glaciers, the Bering Glacier began as a mass of ice that was compressed by immense
pressure under accumulating snow.
Glaciers, like rivers, gradually move from high to low elevations, constantly shifting
and eroding the landscapes around them.
As they move, massive glaciers scour hills and mountain sides, carving U-shaped valleys,
sometimes hundreds of meters deep.
When glaciers melt along the coast, rounded depressions flood with a mix of sea water
and glacial meltwater, creating fertile ecosystems called fjord estuaries.
There are many estuaries in the world, like the Thames Estuary in England and San Francisco
Bay in the western United States.
Unlike these estuaries, fjord estuaries are filled with deep, cold water, which enables
large, open-ocean creatures like whales to live closer to the shore.
In Kenai Fjords National Park, humpback whales migrate over 4,300 kilometers every spring
to feed on krill in this fjord estuary’s nutrient-rich, brackish water.
About 3,500 kilometers south of Kenai Fjords National Park, five million years of running
water, combined with rock uplift, have eroded a deep ravine into the American state of Arizona.
The cliffs of the Grand Canyon, which stand over 1,800 meters tall, were carved by the
Colorado River, which flows across the 336,000-kilometer Colorado Plateau in the southwestern United
States.
The Colorado River is most famous for sculpting one of the world’s natural wonders, but
it is also a life-giving force for some of North America’s driest regions.
Winding its way across the desert, the Colorado River supplies fresh water to a variety of
arid ecosystems, including desert scrub, boreal forests, and pinyon-juniper woods.
Along the Grand Canyon, the Colorado River supports more than 90 species of mammals,
300 species of birds, and 1,700 species of plants.
This rushing river has also played an important role in human history.
For roughly 12,000 years, the Colorado River has provided water for drinking and irrigation
to local communities.
The Puebloans were the first people to build complex masonry structures along the cliffs
that line the Colorado River.
Later, the region was settled by a number of tribes, including the Havasupai, who occupy
parts of the Grand Canyon today.
South of the Equator, the Amazon River Basin spans six densely populated countries and
nourishes the world’s most diverse terrestrial ecosystem, the Amazon Rainforest.
The Amazon River flows from the Andes Mountains in Peru to the coast of Brazil, where it discharges
into the Atlantic Ocean.
The Amazon is the largest river in the world by volume discharged and sustains millions
of species, including colorful birds and playful primates living in the Amazon Rainforest.
The rainforest supports a diverse ecosystem, but it also helps regulate the region’s
tropical climate.
The trees in the Amazon Rainforest recycle precipitation through a process called transpiration.
Every day, billions of trees pump countless tons of water into the atmosphere, creating
flying rivers that influence weather patterns and supply fresh water to millions of people.
The ecological significance of the Amazon Rainforest is rivaled by the Great Barrier
Reef, located on the eastern coast of Australia.
Stretching nearly 2,300 kilometers and containing over 3,000 individual reefs, the Great Barrier
Reef is the largest single structure created by living organisms.
The Great Barrier Reef is made of hard corals.
Corals are marine animals that build calcium carbonate skeletons, forming a reef’s three-dimensional
structure.
Roughly 600 species of corals live in the Great Barrier Reef, alongside more than 1500
species of fish, 215 species of birds, and six of the seven marine turtle species in
the world today.
Tropical coral communities, like the Great Barrier Reef, support 25% of all known marine
life.
These ecosystems also shield coastlines from damaging waves.
Unfortunately, coral communities around the world are rapidly shrinking, due in part to
rises in ocean temperatures.
When tropical waters get too warm, it destroys the delicate, symbiotic relationship between
coral and microscopic algae called zooxanthellae.
Zooxanthellae supply their coral hosts with food, which they produce through photosynthesis.
When ocean temperatures rise, corals expel their microscopic symbionts, causing the coral
to appear white or bleached.
Corals can recover from bleaching, but if ocean temperatures continue to increase, the
majority of coral species will die.
In 2016, a single warming event along the Great Barrier Reef destroyed more than 20%
of its corals.
Scientific models predict a two-degree Celsius increase in ocean temperatures by 2050, which
may destroy up to 99% of the Earth’s coral reefs.
Another natural wonder recently affected by climate change is Victoria Falls, a breathtaking
waterfall in southern Africa.
Located on the Zambezi River, along the border of Zambia and Zimbabwe, Victoria Falls is
the world’s largest curtain of falling water, stretching a remarkable 1,700 meters across.
In 2019, after a long drought driven by climate change, Victoria Falls shrunk from a colossal
waterfall to a mere trickle.
Like the Colorado and Amazon Rivers, the Zambezi River supports a myriad of plants and animals,
but it also played a critical role in the evolution of early humans.
Some scientists believe anatomically modern humans originated in southern Africa, near
the Zambezi river.
Around the river basin, archaeologists have also uncovered dozens of human artifacts,
dating back thousands of years.
The Zambezi River has potentially nurtured human development from the Stone Age all the
way to the modern era.
In all its forms, water has influenced the Earth’s development and topography, creating
a habitable world for millions of species.
Water may be a tasteless, colorless, and transparent substance, but it has transformed the Earth
into the beautiful blue planet we know today.