The carbon cycle

0:00- [Narrator] Take a deep breath, in and out. The carbon dioxide you just exhaled, it might end up in a tree. A few years later, it could settle in a soil, and millions of years from now, it might even become coal. But wait, how does carbon move through all these places?

0:18Let's find out. Carbon is stored in different parts of the environment called the carbon reservoirs. Organic reservoirs include living organisms, like plants, animals, and even microbes. This also includes their remains after they die. Now, inorganic reservoirs include non-living parts of the environment, like rocks, sediments, water, and even the atmosphere.

0:45But what's interesting is that the carbon moves from one reservoir to another in a cycle. So we call this the carbon cycle. But how does it move? You ask. Well, there are four main processes that move carbon through the environment. We have photosynthesis, respiration, decomposition, and combustion.

1:07Let's start with photosynthesis. Plants use sunlight to convert carbon dioxide from the atmosphere into glucose, a type of sugar. Now, processes that remove carbon from the atmosphere are called carbon sinks. So through photosynthesis, plants act as a carbon sink.

1:28Next up, respiration. Respiration is a process in which plants and animals break down glucose to get energy. This process releases carbon dioxide back into the atmosphere. Any process that adds carbon to the atmosphere is called the carbon source. So respiration is a carbon source.

1:49But what happens when plants or animals die? That's where the decomposers come in. Organisms like bacteria and fungi, they break down dead organisms to get energy. This process is called decomposition. And it also releases carbon dioxide back into the atmosphere.

2:07So decomposition is a carbon source as well. Now these three processes: photosynthesis, respiration, and decomposition, make up the biological carbon cycle. This cycle moves carbon between the atmosphere and organisms, and it happens relatively quickly, often within years.

2:27That's why it's also called the fast cycle. But not everything breaks down right away. Some organisms and their remains don't fully decompose. Instead, they get buried under layers of soil and rock. Over millions of years, most of these buried carbon becomes part of sedimentary rocks.

2:47But in certain conditions, like very little oxygen combined with intense heat and pressure, the carbon can turn into fossil fuels like coal, or oil or natural gas. This underground carbon can stay locked away for millions of years. So how does it get unlocked then?

3:08Well, eventually carbon is released back into the atmosphere in two ways, through volcanic eruptions, which releases carbon stored in rocks, or when humans extract and burn fossil fuels for energy. We call that combustion. Both processes release carbon dioxide into the air.

3:26So these processes are also carbon sources. This long-term movement of the carbon through rocks and deep underground is called the geological carbon cycle. And since this takes millions of years to complete, it's also called the slow cycle. So in summary, carbon is always moving from one reservoir to another through living organisms, land, ocean, and deep underground.

3:52The biological carbon cycle happens over days to years. The geological carbon cycle can take millions of years. And remember, carbon isn't created or destroy in a cycle. It just changes form and location. But when we extensively extract and burn fossil fuels, we are taking carbon that was stored deep underground for millions of years and adding it to the atmosphere.

4:15This extra carbon dioxide traps more heat and raises global temperatures, and that's why we need to make an effort to move some of that carbon back into long-term reservoirs like forests or wetlands, mangroves and healthy soils. Planting trees, protecting natural ecosystems and improving land use are all ways we can help keep more carbon stored and reduce the impact of climate change.