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Biosphere & Ocean Absorption of Greenhouse Gases

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we're going to be learning about how the ocean and biosphere help control global warming by absorbing greenhouse gases. We'll look at how this is affecting the Earth and the prognosis for years to come.

What Are Greenhouse Gases?

In 2017, hurricanes pummeled the southern coast of the United States and the Caribbean in close succession. Many islands lost everything, with beaches, cities, and all infrastructure destroyed. In the same year, the worst wildfires in history raged through California while thousands were forced to evacuate. Meanwhile, droughts ripped through Africa and parts of the Antarctica pack ice broke apart during their winter, a time when pack ice should normally refreeze.

What is going on in our world? Human activities are putting increasing amounts of stress on the Earth. Many of our problems stem from the production of greenhouse gases, like carbon dioxide or methane. These gases wrap the Earth like a blanket, trapping heat from the Sun. This is leading to climate change, or an increase in global temperature on Earth. This doesn't simply mean everywhere is getting hotter. Climate change results in rising sea levels, altered chemical composition of the ocean, and large-scale changes in weather patterns that are causing increased numbers of natural disasters.

What Is The Carbon Cycle?

Carbon dioxide cycles through living things, also known as the biosphere; the atmosphere; the oceans; and Earth. Normal processes like breathing and geological activities release carbon dioxide into the atmosphere. Trees take carbon dioxide out of the atmosphere during photosynthesis, and the oceans are also able to absorb some. Over millions of years, the carbon in living things is compressed into fossil fuels deep within the Earth after they die. But, humans are disrupting this process. We are digging up fossil fuels and burning them faster than they can be made. Today, we're going to look at how two specific parts of the carbon cycle are involved in controlling levels of greenhouse gases: the biosphere and the ocean.

Biosphere

Redwood trees are some of the largest living things on Earth, growing up to 360 feet tall. Where do these trees get their mass? Many students might think of water or nutrients, but the answer is actually something invisible - carbon dioxide. Trees take in carbon dioxide and use water and light energy from the Sun to convert it to sugar through the process of photosynthesis. This reduces the amount of carbon dioxide in the atmosphere and helps to mitigate human activities that are driving climate change.

Photosynthesis allows plants to store carbon as sugar
photosynthesis

But, the biosphere includes all living things on Earth, so how is everyone else involved? All living things are made of carbon. Plants take carbon dioxide from the air and make that into carbon-based sugars, like glucose. When herbivores consume the plants, they eat the sugar, and thus the carbon, and use it to make energy, grow, and repair.

But you might be thinking, 'what about the carnivores'? After all, carnivores only eat meat. But, remember, all living things are made of carbon. So, the plants got the carbon from the atmosphere, the herbivores ate those plants, and now the carnivores consume the herbivores and the carbon continues to be passed up the food chain.

But, all good things must come to an end, and eventually, all of these living things will die. When organisms die in a natural ecosystem, their bodies are eaten by scavengers, again passing the carbon onto other parts of the biosphere. Whatever remains will be destroyed by decomposers like worms and fungi and the rest of the carbon will be returned to the soil. Over millions of years, the geologic processes of the Earth will compress those living things into rock, and eventually, they will become fossil fuels like coal and oil.

Oceans

The oceans are one of the most important ecosystems on Earth. Although we usually think of rainforests as providing most of the oxygen for Earth, it's actually our oceans that supply 70% of the oxygen in the atmosphere. If that wasn't enough, our oceans are one of the largest carbon sinks on the planet, meaning a body that can store carbon dioxide.

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