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Why study the carbon cycle?

Carbon is everywhere, in the oceans, in rocks and soils, in all forms of life, and in our atmosphere. Without carbon, life would not exist as we know it. The well-being and functioning of our planet depends on carbon and how it cycles through the Earth's systems.

Carbon is constantly in the news. Have you heard of carbon dioxide and the greenhouse effect? The carbon cycle plays a key role in regulating Earth's global temperature and climate by controlling the amount of carbon dioxide in the atmosphere. The greenhouse effect itself is a naturally occurring phenomenon that makes Earth warm enough for life to exist. Without the greenhouse effect, Earth would be a much colder place. Carbon dioxide is an important greenhouse gas, because it helps Earth's atmosphere to retain heat generated from the Sun. But sometimes, too much of a good thing can have negative consequences. Too much carbon dioxide going into the atmosphere can lead to a planet that gets unnaturally hot.

Since the industrial revolution in the 19th century, carbon dioxide in the atmosphere has risen by 30%. Scientists have shown that this increase in carbon dioxide is a result of human activities that have occurred over the last 150 years, including the burning of fossil fuels and deforestation. Since carbon seems to be connected to everything that matters to us—our climate, our bodies, our ecosystems, the health of our planet—it makes sense for us, scientists and non-scientists alike, to learn as much about carbon and carbon cycle as we can. Only then can we make sensible "carbon decisions" that will impact our future.

What will I learn?

This unit will introduce you to the basics of the carbon cycle. You will learn how the carbon cycle, climate and the abiotic and biotic components of the environment influence each other in many ways. You will learn how carbon moves throughout the different components of the carbon cycle and where carbon is stored in the Earth's system. Using case studies, NASA visualizations, current research, and interactives, you will explore how living things on land, in soils, and in our oceans regulate the carbon cycle. Because carbon, climate and the environment are tightly coupled, you will analyze the effect of carbon dioxide on the Earth's thermostat and our climate. Finally, you will seek possible solutions to a warming climate.

Key Questions

Key questions addressed by this unit include:

How do the carbon cycle, climate and the environment influence each other?

How does carbon move through the Geosphere and the Biosphere, in what forms and at what time and spatial scales?

How is the carbon cycle interconnected with other biochemical cycles such as the nitrogen cycle?

How does the carbon cycle regulate the temperature of Earth's atmosphere?

Will carbon dioxide continue to rise, and if so, what can we do about it?

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Climate and the Carbon Cycle: Unit Overview

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Why study the carbon cycle? Carbon is everywhere, in the oceans, in rocks and soils, in all forms of life, and in our atmosphere. Without carbon, life would not exist as we know it. The well-being and functioning ...

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New research

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New view of how ocean 'pumps' impact climate change

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Earth's oceans have a remarkable natural ability to pull carbon from the atmosphere and store it deep within the ocean waters, exerting an important control on the global climate. A large portion of the carbon dioxide emitted when humans burn fossil fuels, for instance, is taken up and stored in the ocean via a set of processes that make up the ocean carbon cycle.

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Good for why we should care and current news and data.

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Climate Central researches and reports on the impacts of climate change, including sea level rise and coastal flooding, extreme weather and weather attribution, global warming and local temperature trends, carbon dioxide and greenhouse gas emissions.

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Explore the fact-checked online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of objective articles, biographies, videos, and images from experts.

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ThoughtCo.com is the World's Largest Education Resource

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From chemistry to computer programming, arts to World War II, ThoughtCo.com provides guides, tips, and resources to help you understand more about the world around us.

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HowStuffWorks has been explaining how things work to curious minds since 1998. Providing factual, unbiased content that's fun to read and makes difficult topics easy to understand.

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Weathering of minerals role in the Carbon Cycle

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Weathering of minerals role in the Carbon Cycle

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from pp. 176-177 in the book called, "Drawdown" by Paul Hawken

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See the section "Making Rocks"

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T. Schuur

Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA

Highlights

Northern permafrost region soils contain 1,460-1,600 billion metric tons of organic carbon, about twice as much as currently contained in the atmosphere.

This pool of organic carbon is climate-sensitive. Warming conditions promote microbial conversion of permafrost carbon into the greenhouse gases carbon dioxide and methane that are released to the atmosphere in an accelerating feedback to climate warming.

New regional and winter season measurements of ecosystem carbon dioxide flux independently indicate that permafrost region ecosystems are releasing net carbon (potentially 0.3 to 0.6 Pg C per year) to the atmosphere. These observations signify that the feedback to accelerating climate change may already be underway.

Introduction

The Arctic continues to warm at a rate that is currently twice as fast as the global average (see essay Surface Air Temperature). Warming is causing perennially-frozen ground (permafrost) to thaw, with permafrost in many locations currently reaching record high temperatures (Biskaborn et al. 2019). Organic carbon contained in soils of the permafrost region represent a climate-sensitive carbon reservoir that is affected by warming air and ground temperatures and permafrost thaw. This permafrost carbon is the remnants of plants, animals, and microbes that have lived and died in tundra and boreal ecosystems, accumulating in frozen soil over hundreds to thousands of years (Schuur et al. 2008). The northern permafrost region holds almost twice as much carbon as is currently in the atmosphere. Additional net releases of carbon dioxide (CO ₂) and methane (CH ₄) to the atmosphere as a result of warming and faster microbial decomposition of permafrost carbon have the potential to accelerate climate warming. This report details recent advances in quantifying the amount of organic carbon stored in permafrost soils and the current exchange of CO ₂ between tundra and boreal ecosystems and the atmosphere. It updates material included in an essay on the terrestrial carbon cycle that appeared in Arctic Report Card 2016 (Schuur and Hugelius, 2016).

Permafrost carbon pools: How much permafrost carbon is available to release into the atmosphere?

The new, best mean estimate of the amount of organic carbon stored in the northern permafrost region is 1,460-1,600 petagrams (Pg; 1 Pg = 1 billion metric tons) (Hugelius et al. 2014; Schuur et al. 2015). Of this inventory, 65-70% (1,035 ± 150 Pg) of the carbon is within the surface layer (0-3 m depth) (Fig. 1). Soils in the top 3 m of the rest of Earth's biomes (excluding Arctic and boreal biomes) contain 2,050 Pg of organic carbon (Jobbagy and Jackson 2000). The soil carbon from the northern circumpolar permafrost region adds another 50% to this 3-m inventory, even though it occupies only 15% of the total global soil area (Schuur et al. 2015).

A significant amount of carbon (25-30%) is also stored deeper (> 3 m depth) due to unique processes that bury carbon in permafrost region soils. In particular, the Yedoma region of Siberia and Alaska remained ice-free during the last Ice Age and accumulated silt (loess) soils, which buried large quantities of organic matter deep into the permafrost (Strauss et al. 2013). Recent work has reconciled several estimates for the Yedoma region, placing 327-466 Pg C in these deep loess deposits, which can be tens of meters thick (Schuur et al. 2018). This region contains intact Yedoma deposits that have remained primarily frozen since the last glacial period, and also deposits where abrupt permafrost thaw led to ground subsidence ( thermokarst) and lake formation. These thermokarst lakes accumulated more carbon as lake ecosystems developed, and these deposits later re-froze into permafrost when the lakes drained (Anthony et al. 2014; Strauss et al. 2017). The remaining deep carbon accounted for in the total permafrost carbon inventory is contained in Arctic river deltas, which contain 96 ± 55 Pg C (< 10%).

Permafrost thaw occurs when a warming climate affects permafrost temperature gradually from the surface downward. At the same time, abrupt permafrost thaw, related to the destabilization of and melting of ground ice, can affect tens of meters of permafrost rapidly over a single season. As a result, the entire organic carbon inventory of surface and deep soil reported here may be vulnerable to thaw in a changing climate.

Ecosystem-atmosphere carbon exchange: Is the Arctic currently releasing additional net carbon dioxide emissions to the atmosphere?

Permafrost thaw and increased microbial decomposition releases stored organic carbon from the terrestrial biosphere into the atmosphere as greenhouse gases. At the same time, plant growth sequesters atmospheric CO ₂, which becomes stored as new plant biomass or deposited as new soil organic matter. Direct and indirect effects linked to climate warming can stimulate both processes, and whether Arctic ecosystems are currently a net carbon source (losses > gains) or sink (gains > losses) is an area of intense research. Ecosystem carbon balance (net gain or loss of ecosystem carbon) is the relatively small difference between two large, opposing fluxes: plant carbon uptake via plant photosynthesis and growth versus respiratory loss via metabolism by all living organisms (Fig. 2). Across the landscape, this biological carbon cycle is then modified by relatively rapid physical disturbances, such as fire and abrupt permafrost thaw (thermokarst) that accelerate carbon losses while modifying rates of carbon gain. Carbon dioxide represents the main form, by weight, of carbon exchanged between ecosystems and the atmosphere. Methane exchange is a much smaller amount by weight than CO ₂, and consequently does not greatly alter ecosystem carbon balance at the landscape scale. The larger warming potential of CH ₄ means that changing emissions can affect climate, but these impacts are outside of the scope of this report.

Northern tundra and boreal ecosystems typically gain carbon ( carbon sink) stored in plant biomass and new soil organic matter during the short summer growing season when plant photosynthesis and growth is greater than carbon respired by plants and soil back to the atmosphere. In any given year, individual ecosystems can have gains or losses in net carbon due to changes in the physical and biological environment (Treat et al. 2018), and also depending on the successional stage of the ecosystem, but what matters to future climate is the aggregate response across the regions over years to decades.

Previous efforts to synthesize ecosystem carbon balance focused on CO ₂ flux measurements have produced results that have not agreed. For instance, a study that scaled plot CO ₂ flux measurements to regional land area reported a net annual carbon exchange in the tundra region of 0.013 Pg C per year (i.e., a small sink but near neutral exchange) over the 1990s and 2000s (McGuire et al. 2012). A follow-up study focused on a subset of the same tundra sites and also included new sites with additional non-summer data to bolster the under-sampled cold season (Belshe et al. 2013). The second study supported the previous finding that the summer-season carbon sink increased in the 2000s compared with the 1990s. However, the second study also suggested that the mean tundra flux remained a carbon source annually across both decades when additional non-summer flux data were included. When scaled to a similar-sized region, the second study predicted that the tundra was acting as a current source of 0.462 Pg C per year. One potential explanation for the difference between these two comprehensive synthesis studies was the inclusion (in the former), and exclusion (in the latter) of fluxes measured in wetland ecosystems. Wetlands generally store more carbon in anaerobic soils, and typically act as annual net carbon sinks even while CH ₄ is emitted (Lund et al. 2010). This differential response of individual ecosystem types and the relative scarcity of measurement sites across the Arctic region continue to make it difficult to upscale to the aggregate effect of ecosystems' greenhouse gas exchange on the atmosphere.

Another approach to this same question is to measure changes in atmospheric greenhouse gas concentrations and to separate out contributions from different sources. Given the extent of fossil fuel carbon emissions, it remains a challenge to quantify and separate the effect of ecosystem carbon exchange, but regional atmospheric measurement campaigns can help to focus in on local influences (Parazoo et al. 2016). Recent measurements of atmospheric greenhouse gas concentrations over Alaska by NASA aircraft have been used to the estimate the net regional impact on the atmosphere by those Arctic and boreal ecosystems for 2012 to 2014 (Commane et al. 2017). This recent NASA campaign was able to provide important insight into the aggregate influence of the carbon exchange for the Alaska permafrost region, across tundra, boreal forests, and wetland/lake/freshwater ecosystems as a whole. During this three-year time period, the tundra region of Alaska was found to be a consistent net CO ₂ source to the atmosphere, whereas the boreal forest region was either neutral or a net CO ₂ sink. The boreal forest region exhibited larger interannual variability due both to changes in the balance of photosynthesis and respiration and to the amount of combustion emissions by wildfire.

The Alaska study region as a whole was estimated to be a net carbon source of 0.025 ± 0.014 Pg C per year averaged over the land area of both tundra and boreal forest regions for the three-year study period. If this Alaskan region (1.6 × 10 ⁶ km ²) was representative of the entire northern circumpolar permafrost region soil area (17.8 × 10 ⁶ km ²), this amount would be equivalent to a circumpolar net source of 0.3 Pg C per year. Historically (over hundreds to thousands of years), the Arctic region was accumulating carbon in soils and vegetation and thus was acting as a net sink of atmospheric CO ₂. Assuming this three-year snapshot provided by NASA aircraft monitoring is indicative of the Arctic's current physical and biological environment, a significant and major threshold has been crossed in the high latitude region whereas the aggregate effect of terrestrial ecosystems is now contributing to, rather than slowing, climate change.

Aircraft measurements of atmospheric greenhouse gas concentrations help to describe the combined regional impact of changing permafrost region ecosystems. However, the long cold Arctic winter (or non-summer) season limits observations from the air, just as it has limited ground-based observations in the past due to the difficult operating conditions. For example, the NASA aircraft campaign made atmospheric measurements from April through November only. In one of the recent synthesis studies of ground-based measurements, the regional carbon balance estimate for the North American subregion, for example, had 80 study-years of summer measurements and only 9 study-years of non-summer measurements available for upscaling (McGuire et al. 2012). The summer growing season is typically a time when net carbon is stored within growing ecosystems acting as a seasonal carbon sink. However, summer carbon sequestration is partially offset by carbon losses in fall, winter, and spring when microbes remain metabolically active and release CO ₂ during a period where plants are largely dormant. While absolute levels of CO ₂ flux are low during the non-summer season, the long period of more than 250 days can be enough to offset the net carbon that accumulated during summer.

A new comprehensive synthesis study of non-summer ecosystem CO ₂ fluxes across the circumpolar region showed that carbon release during the Arctic winter was 2 to 3 times higher than previously estimated from ground-based measurements (Fig. 3) (Natali et al. 2019). This circumpolar estimate suggests that carbon release in the cold season offsets net carbon uptake during the growing season (derived from models) such that the region as a whole could already be a source of 0.6 Pg C per year to the atmosphere. It was not possible to determine whether these higher flux estimates were a result of changing environmental conditions or the aggregation of more observations during this scarcely observed non-summer period. Regardless, similar to the regional extrapolation made by aircraft, this winter flux synthesis supports the idea that the accelerating feedback from changing permafrost ecosystems to climate change may already be underway.

References

Belshe, F. E., A. G. Schuur, and B. M. Bolker, 2013: Tundra ecosystems observed to be carbon dioxide sources due to differential amplification of the carbon cycle. Ecol. Lett., https://doi.org/10.1111/ele.12164.

Lund, M., and Coauthors, 2010: Variability in exchange of CO ₂ across 12 northern peatland and tundra sites. Glob. Change Biol., 16(9), 2436-2448, https://doi.org/10.1111/j.1365-2486.2009.02104.x.

Natali, S., and Coauthors, 2019: Large loss of CO ₂ in winter observed across pan-Arctic permafrost region. Nat. Climate Change, 9, 852-857, https://doi.org/10.1038/s41558-019-0592-8.

Parazoo, N. C., R. Commane, S. C. Wofsy, C. D. Koven, C. Sweeney, D. M. Lawrence, J. Lindaas, R. Y. -W. Chang, and C. E. Miller, 2016: Detecting regional patterns of changing CO ₂ flux in Alaska. P. Natl. Acad. Sci. USA, 113(28), 7733-7738, https://doi.org/10.1073/pnas.1601085113.

Schuur, E. A. G., and Coauthors, 2008: Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle. Bioscience, 58, 701-714.

Schuur, E. A. G., and Coauthors, 2018: Chapter 11: Arctic and boreal carbon. In: Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report, Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu, Eds., U.S. Global Change Research Program, Washington, DC, USA, 428-468.

Schuur, T., and G. Hugelius, 2016: Terrestrial carbon cycle. Arctic Report Card 2016, J. Richter-Menge, J. E. Overland, and J. Mathis, Eds. http://www.arctic.noaa.gov/Report-Card.

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T. Schuur Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA Highlights Northern permafrost region soils contain 1,460-1,600 billion metric tons of organic carbon, about twice as much as currently contained in the atmosphere. This pool of organic carbon is climate-sensitive.

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an article from The New York Times

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A short textbook about Ocean Acidification with many short chapters.

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The ocean plays an important role in the global carbon cycle. Carbon moves in and out of the ocean daily, but it is also stored there for thousands of years.

The carbon cycle

Carbon is a chemical element vital to all living things and is present in many non-living things. Carbon circulates around the planet in what is called the carbon cycle. Parts of the cycle store carbon for different lengths of time, and there are many processes that move carbon in and out of the stores.

Find out more about the carbon cycle in the interactive.

Carbon moves through the carbon cycle in stops and starts. An individual atom might pass through plants, animals and the atmosphere in a matter of days, yet stay trapped in rocks for millions of years.

Plants exchange carbon with the atmosphere every day as they make and use carbohydrates for energy, but plants also store carbon because they use it to build their structures - some trees store carbon for hundreds of years. This carbon only moves on again if the tree dies and decays or is burnt. Carbon can be stored for much longer periods too - for thousands of years in the ocean or for millions of years in rocks.

Changes to the carbon cycle

Systems do not stay the same - when one part is changed, other parts respond and change to restore a balance. Over the last 200 years or so, there has been a detectable change in the carbon cycle. Humans have been burning carbon-rich fossil fuels, releasing carbon dioxide into the atmosphere. This has been releasing carbon that would normally be stored in the geosphere. Even the carbon dioxide put into the atmosphere by all the volcanoes that erupt in a year is only a hundredth of that released by human activity.

The ocean removes about half the extra carbon dioxide from the atmosphere and increased plant growth removes more through photosynthesis, but the level of carbon dioxide in the atmosphere is still rising. Carbon dioxide is one of the greenhouse gases that stops heat escaping from the planet. More carbon dioxide in the atmosphere, means more heat trapped, resulting in an increase in temperature - this is contributing to climate change.

The ocean and carbon

The ocean plays an important part in the carbon cycle. Overall, the ocean is called a carbon 'sink' because it takes up more carbon from the atmosphere than it gives up.

Carbon dioxide from the atmosphere dissolves in the surface waters of the ocean. Some of the carbon dioxide stays as dissolved gas, but much of it gets turned into other things. Photosynthesis by tiny marine plants (phytoplankton) in the sunlit surface waters turns the carbon into organic matter. Many organisms use carbon to make calcium carbonate, a building material of shells and skeletons. Other chemical processes create calcium carbonate in the water. The using up of carbon by biological and chemical processes allows more carbon dioxide to enter the water from the atmosphere.

Biological pump

Living things in the ocean move carbon from the atmosphere into surface waters then down into the deeper ocean and eventually into rocks. This action of organisms moving carbon in one direction is often called a biological pump.

Carbon gets incorporated into marine organisms as organic matter or structural calcium carbonate. When organisms die, their dead cells, shells and other parts sink into deep water. Decay releases carbon dioxide into this deep water. Look at the carbon cycle interactive to see how much carbon is in the deep ocean compared to other stores. Some material sinks right to the bottom, where it forms layers of carbon-rich sediments. Over millions of years, chemical and physical processes may turn these sediments into rocks. This part of the carbon cycle can lock up carbon for millions of years.

Related content

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The ocean plays an important role in the global carbon cycle. Carbon moves in and out of the ocean daily, but it is also stored there for thousands of years. Carbon is a chemical element vital to all living things and is present in many non-living things.

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Humans, just like all other living organisms, have impacted the global carbon cycle since the dawn of our species. However, the magnitude of our impacts has changed dramatically throughout history. The Industrial Revolution, which occurred around the turn of the 19th century, began to make major changes in the use of resources around the world. Beginning in Britain, industrialization eventually affected the whole world. The development of coal-fueled steam power, and later transportation following the discovery of large oil deposits, had enormous influence on the economic and social structure of the world. As the world accelerated in the production and transportation of manufactured goods, the production and consumption of fossil fuels grew. As economic growth continued to increase, so did the production of carbon dioxide through fossil fuel combustion. See Figure \(\PageIndex{2}\) later in this text.

Some of the human impacts on the carbon cycle have been quantified for you in Figure 7.1.1. Changes to fluxes in the carbon cycle that humans are responsible for include: increased contribution of CO ₂ and other greenhouse gases to the atmosphere through the combustion of fossil fuels and biomass; increased contribution of CO ₂ to the atmosphere due to land-use changes; increased CO ₂ dissolving into the ocean through ocean-atmosphere exchange; and increased terrestrial photosynthesis. The first two impacts, both contributing excess CO ₂ to the atmosphere at a rate of 4 Gt of carbon per year have, by far, the largest impact on our planet. For this reason, this is the change that we will most often focus on throughout this section. The excess CO ₂ in the atmosphere is responsible for the increased CO ₂ dissolving into the ocean, which we will discuss later in this section. This is also, in part, responsible for the increased terrestrial photosynthesis that can be observed, as additional CO ₂ is available to plants for photosynthesis. However, intensive agricultural and forestry practices also contribute to the change in this flux.

One characteristic example of a human impact on the carbon cycle is illustrated in Figure \(\PageIndex{1}\). Throughout most of our recent human history, people have been physically altering the landscape around them in order to have more control over their surroundings and increase their odds of survival. One way that people have done this is through agriculture. In order for most forms of agriculture to be successful, native vegetation is eliminated or minimized. Resources from this native vegetation, such as wood, may be used for combustion to provide heat, sanitation, or fuel for cooking. Combustion may also be used as an efficient way to clear the land and make way for crops or grazing lands for livestock. Often, settlements are formed around these newly fashioned agricultural fields, and the land is used in a similar fashion for many years in the future.

Let's identify the ways in which humans are impacting the carbon cycle in this scenario of agricultural establishment. You should be able to identify from the above paragraph that the flux of combustion will release CO ₂ previously held in vegetation into the atmosphere. In addition, remember that the land that used to house native vegetation is now home to agricultural lands. In most controlled agricultural environments, there is less total vegetative biomass than there would be under natural conditions. This decreased biomass leads to lower total photosynthesis rates, thereby decreasing the amount of CO ₂ that is removed from the atmosphere and turned into plant biomass. Also, open soil on the fields between crops, during the winter months, or as a result of overgrazing allows for the air to penetrate deep into the soil structure. This provides the environment necessary for enhanced aerobic respiration by soil microorganisms. This decreases soil carbon, which can lead to erosion and soil degradation, and also releases additional CO ₂ to the atmosphere.
Figure \(\PageIndex{1}\): Impacts of slash and burn agriculture and biomass burning. a) Slash and burn agriculture in Maaninka, Finland. This kind of agriculture was still in use in Finland at the end of the 1920s. b) Slash and burn agriculture at the margins of the Amazon Rainforest in South America captured by astronauts on the International Space Station in August, 2014. Credit: Astronaut photograph ISS040-E-103496. c) Global distribution of biomass fires, represented by red, orange, and yellow dots (lighter colors indicates more fires), based on nighttime measurements obtained by the DMSP Operational Linescan System. Credit: Julia Cole, NASA Earth Observatory
As you learned in Chapter 5, biomass is an important form of energy to human civilization. Prior to the Industrial Revolution, this was essentially the only form of fuel to which most people on Earth had access. In many less-industrialized countries, combustion of biomass such as wood or animal dung is still the primary energy source that many citizens, particularly in rural areas, depend on for domestic use (heating, sanitation, and cooking) as it is inexpensive, relatively efficient, and readily available. Figure \(\PageIndex{1}\)c shows the global distribution of biomass fires in the world. While the burning of biomass for domestic use contributes to some of these fires, it is the so-called slash-and-burn agriculture that makes up a larger contribution. Take a minute to compare the areas highlighted in Figure \(\PageIndex{1}\)c to the countries of the world that are currently experiencing rapid population growth (Chapter 3). If you need a refresher, use the CIA World Factbook website to view current global population growth values by country: www.cia.gov/library/publicat.../2002rank.html.

While biomass burning still has a significant impact on the global carbon cycle, human impacts on fluxes such as fossil fuel extraction and combustion continue to grow. For a review of the impacts of non-renewable energy sources such as fossil fuels, see Chapter 4. Burning of any fossil fuel (coal, natural gas, crude oil) moves carbon from a previously-sequestered state deep within the Earth's crust into carbon dioxide in the atmosphere. As countries become more industrialized, their reliance on and combustion of fossil fuels tends to increase. Look at the graph in Figure \(\PageIndex{2}\), which compares CO ₂ emissions from fossil fuels of regions across the globe.

How has the use and distribution of fossil fuels changed throughout the past 250 years?
Figure \(\PageIndex{2}\): Total annual CO₂ emissions from fossil fuel combustion 1850-2011 by global region. Data from the Carbon Dioxide Information Analysis Center (CDIAC) cdiac.esd.ornl.gov/
The data shown in Figure \(\PageIndex{2}\) reveals much about the regions of the world it depicts. The effects of historic events such as the Great Depression of 1929-1939, World Wars, the fall of the Soviet Union in 1991, and the Kuwait oil fires of 1991 can be seen. Furthermore, between 1850 and 2011, different regions have gone in and out of the lead position as top producer of CO ₂ from fossil fuel emissions. Population is one reason why fossil fuel use has changed throughout time. This is particularly apparent when comparing the data for Western Europe to that of India and Southeast Asia.

As countries industrialize, their relationship with agriculture also changes. More-industrialized countries rely very little on slash-and-burn agriculture. Their agricultural practices, however, are no less impactful on the environment. The growing population (Chapter 3) in many countries has required agriculture to become industrialized in order to meet demand. As a person living in the United States, industrialized agriculture probably produces the vast majority of the food you eat, including grains, fruits and vegetables, dairy and eggs, meats, and even fish. Industrialized agriculture can refer to a variety of practices, but has several main components: the use of motorized machinery; the use of chemicals such as fertilizers, pesticides, hormones, and/or antibiotics; and the intense and efficient production of one product across a large area of land.
Figure \(\PageIndex{3}\): US methane emissions by source. 36% of the US methane production comes from agriculture: enteric fermentation (production of methane by anaerobic bacteria within the ruminant gut) and manure management. All emissions estimates from the Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2013. US EPA
One example of the impacts of industrialized agriculture is the production of methane (CH ₄), a potent greenhouse gas. You will learn more methaneabout methane later in this section. As you saw earlier, methane is a common product of anaerobic metabolisms. The gut of ruminant animals (such as sheep, cattle, and goats) has evolved to allow the animals to digest the very tough carbon molecules, such as cellulose, in grass. They do this through symbiosis, or cooperation, with anaerobic bacteria who live in the gut tract. These anaerobic bacteria produce methane and other gases as a result of their metabolism when they break down molecules like cellulose. This is sometimes called enteric fermentation. The methane gas is excreted from the animal, and this contributes significantly to total methane emissions (Figure \(\PageIndex{3}\)). A similar type of bacteria live in the fecal matter, or manure, of livestock. As the manure is handled or stored for future use, methane is also released to the environment.

The methane excretions of one cow or a few sheep would be miniscule and insignificant. If you were a small farmer with only enough livestock to feed your family, your contribution to total methane emissions would be close to zero. However, the demand for animal protein from meat, dairy, and eggs is very large in the United States. As of January 2015, the United States had a total cattle inventory of 89.9 million animals, and in 2014, 25.5 billion pounds of beef was consumed in the United States (statistics: National Cattlemen's Beef Association). The impacts of enteric fermentation and manure management for almost 90 million animals are very significant, as seen in Figure \(\PageIndex{3}\). In both cases, carbon that was previously stored in biomass (cattle feed) is moved into the atmosphere, this time in the form of CH ₄. This is another example of how humans have impacted the carbon cycle.

Previously in this chapter, you identified other ways the carbon cycle is impacted by human agriculture. Through industrialized agriculture, we must also account for the fossil fuels that are used. In order to deliver agricultural products to consumers, fossil fuels are used numerous times: deliveries of fertilizer, feed, and/or seed to farms; farm machinery; delivery of products to processers; food processing; delivery of foods to supermarkets; etc.

As animal products, especially meat, are expensive, the demand is typically greater in more industrialized countries than it is in less-industrialized countries. This makes industrialized agriculture, and especially industrialized animal agriculture, one of the major contributors to greenhouse gas emissions in more-industrialized countries.

Knowledge check - answer these questions on your own to further explore the impacts of biomass and fossil fuel burning on the global carbon cycle.

1. Why is there a correlation between population growth rate and global distribution of biomass fires?

2. Do you think this correlation is more likely due to personal biomass fires for activities such as cooking, or due to slash-and-burn agriculture? Why?

3. Given any other knowledge you might have about the areas highlighted in Figure \(\PageIndex{1}\)c, what other environmental impacts may be occurring here besides carbon cycle alterations?

4. Compare the production of CO ₂ emissions from fossil fuel combustion across world regions in 1900, 1950, and 2011 in Figure \(\PageIndex{2}\). What has accounted for these differences?

5. Has the total worldwide production of CO ₂ from fossil fuels increased evenly relative to human population growth during the time period displayed in Figure \(\PageIndex{2}\)? Why or why not?

6. What are the differences in contributions of greenhouse gas emissions from more industrialized countries and less-industrialized countries? What are the similarities?

Terms list

Aerobic

Less-industrialized country

Anaerobic

Lithosphere

Autotroph

Methane

Biomass

More-industrialized country

Carbon

Nitrous oxide

Carbon dioxide

Ocean-atmosphere

Cellular respiration exchange

Chloroplast

Photosynthesis

Combustion

Potential energy

Consumption

Primary producer

Decomposition

Reservoir

Equilibrium

Residence time

Flux

Ruminant animal

Greenhouse gas

Sink

Heterotroph

Slash-and-burn agriculture

Industrial Revolution

Source

Industrialized agriculture

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Humans, just like all other living organisms, have impacted the global carbon cycle since the dawn of our species. However, the magnitude of our impacts has changed dramatically throughout history. The Industrial Revolution, which occurred around the turn of the 19th century, began to make major changes in the use of resources around the world.

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Forests are good carbon sinks as long as they're managed and remain as forests. Management and forest products can significantly increase the amount of sequestered carbon and reduce additions from fossil fuels.

Carbon has become a growing issue with forests and forest management, usually spoken about in terms of carbon dioxide and climate effects.

There are conflicting schools of thoughts about the role of forest management and use of wood products. The research background is extensive and growing rapidly. The bulk of that research demonstrates that management and wood products are critical to reduce the effects of rising carbon dioxide levels in the atmosphere. Forests can also be managed to become more resilient in the face of potential climate change patterns.

Jim Bowyer and others summarize the carbon role of forests in four tenets:

1. Keep forests as forests and manage appropriate forests for carbon.

2. Recognize that substantial quantities of carbon are stored in wood products for long periods of time.

3. The substitution effect is immediate, irreversible and cumulative.

4. It is imperative in policy development that objective, science-based analyses are used, that holistic thinking that encompasses the full suite of options in forest management be employed, and that particularly close attention be paid to assumptions and models underlying analyses.

To better understand this somewhat counter-intuitive idea, envision various pools where carbon is stored. There are pools in forests, the oceans, the soil and the atmosphere. The carbon volumes vary from pool to pool. Carbon also cycles normally among the pools both naturally and through human activity.

The carbon balance in the forest pool varies with the age of the forest, the volume of timber and other forest factors. Moving carbon from the atmosphere into forests is called sequestration. However, forests will not sequester carbon forever. Older forests may actually become carbon emitters.

Management helps keep forests younger and more rapidly sequestering carbon. However, harvesting forests also releases carbon, at least temporarily. Some of that carbon goes into deep soils (long storage times) and some temporarily moves into the atmosphere, from whence it came. Within a few years, that atmospheric carbon is re-absorbed by forests or other normal pools. The overall balance is maintained, as long as forest acreage remains.

A large pool, sometimes referred to as a "sink," outside the normal carbon cycle lies within wood products, especially lumber and landfills, about 28 to 29 million tons annually between 2005 and 2007 in the United States. That's about 12-13 percent of what the U.S. forests sequester each year. Growing this pool has advantages.

Together, annual forest growth and wood products sequester between 12-19 percent of total annual fossil fuel emissions. This percentage could be larger.

Additionally, a "substitution effect" increases the value of management and wood products in reducing carbon dioxide effects. When wood is used in place of other raw materials, considerably less fossil fuel is consumed. Construction materials such as concrete, metals and plastics use many times more fossil fuel for extraction, processing and distribution.

Carbon from burning fossil fuels comes from sources outside the normal carbon cycle. Fossil fuel carbon has been stored for millions of years from when the earth was a different kind of place. Over the past 50-75 years, massive quantities of this ancient carbon have been released. Substituting wood products for other raw materials substantially reduces the inflation of the normal carbon cycle.

Most scientists agree that increasing atmospheric carbon (enlarging the normal carbon cycle) has begun to affect Earth's climate. Reducing the use of fossil fuels is one counter-active measure. More managed forest and use of forest products is another.

Forest management already provides revenue streams, economic benefits, environmental services, healthy forests and expanded recreational opportunities. A tool for carbon management can be added to the list of benefits.

For more information, visit these websites:
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Forests play a key role in the global carbon cycle and climate change

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Forests are good carbon sinks as long as they're managed and remain as forests. Management and forest products can significantly increase the amount of sequestered carbon and reduce additions from fossil fuels. Carbon has become a growing issue with forests and forest management, usually spoken about in terms of carbon dioxide and climate effects.

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Deforestation-Effects on the Carbon Cycle

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Deforestation-Effects on the Carbon Cycle

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Human Influences on the Global Carbon Cycle

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Human Influences on the Global Carbon Cycle

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Human Influences on the Global Carbon Cycle

Processes of Carbon Flow in the Human Realm

Humans have exerted an enormous influence on the global carbon cycle, largely through deforestation and fossil fuel burning. In this section, we explore how these processes have led to changes in the dynamics of carbon in the atmosphere.

Fossil Fuel Burning

Another pathway for carbon to move from the sedimentary rock reservoir to the atmosphere is through the burning of fossil fuels by humans. Fossil fuels include petroleum, natural gas, and coal, all of which are produced by slow transformation of organic carbon deposited in sedimentary rocks - essentially the fossilized remains of marine and land plants. In general, this transformation takes many millions of years; most of the oil and gas we now extract from sedimentary rocks is on the order of 70-100 million years old. New fossil fuels take a very long time to form, and we are using them up much, much faster than they are being formed, meaning that if we keep using fossil fuels at the rate we are today, we will run out! This run out date depends on new discoveries and our ability to extract fuels more efficiently by processes like fracking, but we will be close to running out late this century.

These fossil fuels are primarily composed of carbon and hydrogen. For instance, methane, the main component of natural gas, has a chemical formula of CH ₄; petroleum is a more complex compound, but it, too, involves carbon and hydrogen (along with nitrogen, sulfur, and other impurities). The combustion of fossil fuels involves the use of oxygen and the release of carbon dioxide and water, as represented by the following description of burning natural gas:

Beginning with the onset of the industrial revolution at the end of the last century, humans have been burning increasing quantities of fossil fuels as our primary energy source.

As a consequence, the amount of CO 2 emitted from this burning has undergone an exponential rise that follows the exponential rise in the human population. The magnitude of this flow is currently about 9 Gt C/yr. This number also includes the CO ₂ generated in the production of cement, where limestone is burned, liberating CO ₂.

As you can see in the graph above, this flow has changed considerably over time, as human population has increased and as our economies have become more industrialized with a big thirst for the energy provided from the combustion of fossil fuels. The model we will work within the lab activity for this module includes this history, beginning in 1880 and going up to 2010; beyond 2010 is the realm of future projections, which can be altered to explore the consequences of choices we might make or not make in the future. Part of the new energy economy that is key to our future is the use of so-called renewable energy sources, including wind, solar and geothermal energy, that emit little or no carbon. There are some interesting map view representations of this history of fossil fuel carbon emissions in the video below:

Video: Annual Fossil-Fuel CO2 Emissions (2:03) This video is not narrated.

If the video does not play, you can view it at YouTube: Annual Fossil-Fuel CO2 Emissions

Land-Use Changes - Forest Burning and Soil Disruption

The other form of human alteration of the global carbon cycle is through forest cutting and burning and the disruption of soils associated with agriculture. When deforestation occurs, most of the plant matter is either left to decompose on the ground, or it is burned, the latter being the more common occurrence. This process reduces the size (the mass) of the land biota reservoir, and the burning adds carbon to the atmosphere. Land-use changes other than deforestation can also add carbon to the atmosphere. Agriculture, for instance, involves tilling the soil, which leads to very rapid decomposition and oxidation of soil organic matter. This means that in terms of a system, we are talking about two separate flows here - one draining the land biota reservoir, the other draining the soil reservoir; both flows transfer carbon to the atmosphere. Current estimates place the total addition to the atmosphere from forest burning and soil disruption at around 2-3 Gt C/yr; estimates divide this into 70% to 50% forest burning, with soil disruption making up the remainder. Deforestation is a particular problem in the Amazon, as we will see in Module 9.

Deforestation

The actual history of this alteration to the natural carbon cycle is not well-constrained - not nearly as well known as the fossil fuel burning history - but we include a reasonable history that reflects patterns of land settlement and forest clearing.

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Human Influences on the Global Carbon Cycle

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Processes of Carbon Flow in the Human Realm Humans have exerted an enormous influence on the global carbon cycle, largely through deforestation and fossil fuel burning. In this section, we explore how these processes have led to changes in the dynamics of carbon in the atmosphere.

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NASA Earth Observatory- The Carbon Cycle

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NASA Earth Observatory- The Carbon Cycle

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Carbon flows between the atmosphere, land, and ocean in a cycle that encompasses nearly all life and sets the thermostat for Earth’s climate. By burning fossil fuels, people are changing the carbon cycle with far-reaching consequences.

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Organic matter is a key component of soil that affects its physical, chemical, and biological properties, contributing greatly to its proper functioning on which human societies depend. Benefits of soil organic matter (SOM) include improvement of soil quality through increased retention of water and nutrients, resulting in greater productivity of plants in natural environments and agricultural settings. SOM improves soil structure and reduces erosion, leading to improved water quality in groundwater and surface waters, and ultimately to increased food security and decreased negative impacts to ecosystems. Since the beginnings of recorded history, societies have understood that human activities can deplete soil productivity and the ability to produce food (McNeill and Winiwarter 2004). Only in recent history has the understanding of soil productivity been tied to SOM levels, with the depletion of SOM stocks often leading to large-scale impacts on whole ecosystems as well as the entire planet. For example, destruction of rainforests that hold a significant amount of the carbon stored in terrestrial ecosystems contributes significantly to rising atmospheric carbon dioxide (CO ₂) levels linked to climate change, while reductions in SOM levels from soil disturbance from mining can impact infiltration of rainfall and the storage of soil moisture important for flood mitigation. Soil disturbance also leads to increased erosion and nutrient leaching from soils, which have led to eutrophication and resultant algal blooms within inland aquatic and coastal ecosystems, ultimately resulting in dead zones in the ocean (Fig. 1). Restoration of organic matter levels in soil requires an understanding of the ecological processes important for SOM storage. Proper restoration techniques can help restore terrestrial ecosystem functions.

Soil organic matter is composed of soil microbes including bacteria and fungi, decaying material from once-living organisms such as plant and animal tissues, fecal material, and products formed from their decomposition. SOM is a heterogeneous mixture of materials that range in stage of decomposition from fresh plant residues to highly decomposed material known as humus. SOM is made of organic compounds that are highly enriched in carbon. Soil organic carbon (SOC) levels are directly related to the amount of organic matter contained in soil and SOC is often how organic matter is measured in soils.

SOC levels result from the interactions of several ecosystem processes, of which photosynthesis, respiration, and decomposition are key. Photosynthesis is the fixation of atmospheric CO ₂ into plant biomass. SOC input rates are primarily determined by the root biomass of a plant, but also include litter deposited from plant shoots. Soil C results both directly from growth and death of plant roots, as well as indirectly from the transfer of carbon-enriched compounds from roots to soil microbes. For example, many plants form symbiotic associations between their roots and specialized fungi in the soil known as mycorrhizae; the roots provide the fungi energy in the form of carbon while the fungi provide the plant with often-limiting nutrients such as phosphorus. Decomposition of biomass by soil microbes results in carbon loss as CO 2 from the soil due to microbial respiration, while a small proportion of the original carbon is retained in the soil through the formation of humus, a product that often gives carbon-rich soils their characteristic dark color (Fig. 2). These various forms of SOC differ in their recalcitrance, or resistance to decomposition. Humus is highly recalcitrant, and this resistance to decomposition leads to a long residence time in soil. Plant debris is less recalcitrant, resulting in a much shorter residence time in soil. Other ecosystem processes that can lead to carbon loss include soil erosion and leaching of dissolved carbon into groundwater. When carbon inputs and outputs are in balance with one another, there is no net change in SOC levels. When carbon inputs from photosynthesis exceed C losses, SOC levels increase over time.

Photosynthesis, decomposition, and respiration rates are determined partly by climatic factors, most importantly soil temperature and moisture levels. For example, in the cold wet climates of the northern latitudes, rates of photosynthesis exceed decomposition resulting in high levels of SOC (Fig. 3). Arid regions have low levels of SOC mostly due to low primary production, while the tropics often have intermediate SOC levels due to high rates of both primary productivity and decomposition from warm temperatures and abundant rainfall. Temperate ecosystems can have high primary productivity during summer when temperature and moisture levels are highest, with cool temperatures during the rest of the year slowing decomposition rates such that organic matter slowly builds up over time (Fig. 4). While climatic conditions largely generate global patterns of soil carbon, other factors that vary on smaller spatial scales interact with climate to determine SOC levels. For example, soil texture - the relative proportions of sand, silt, and clay particles that make up a particular soil - or the mineralogy of those soil particles can have a significant impact on soil carbon stocks. Additionally, the processes of erosion and deposition act to redistribute soil carbon according to the topography of the landscape, with low-lying areas such as floodplains often having increased SOC relative to upslope positions.

The amount of C in soil represents a substantial portion of the carbon found in terrestrial ecosystems of the planet. Total C in terrestrial ecosystems is approximately 3170 gigatons (GT; 1 GT = 1 petagram = 1 billion metric tons). Of this amount, nearly 80% (2500 GT) is found in soil (Lal 2008). Soil carbon can be either organic (1550 GT) or inorganic carbon (950 GT). The latter consists of elemental carbon and carbonate materials such as calcite, dolomite, and gypsum (Lal 2004). The amount of carbon found in living plants and animals is comparatively small relative to that found in soil (560 GT). The soil carbon pool is approximately 3.1 times larger than the atmospheric pool of 800 GT (Oelkers & Cole 2008). Only the ocean has a larger carbon pool, at about 38,400 GT of C, mostly in inorganic forms (Houghton 2007).

There is a growing body of evidence supporting the hypothesis that the earth's climate is rapidly changing in response to continued inputs of CO ₂ and other greenhouse gases (GHGs) to the atmosphere resulting from human activities (IPCC 2007). While a suite of GHGs exist (e.g., N ₂O, CH ₄), CO ₂ has the largest effect on global climate as a result of enormous increases from the preindustrial era to today. Atmospheric CO ₂ concentrations have risen from approximately 280 parts per million (ppm) prior to 1850, to 381.2 ppm in 2006 (WMO 2006), with a current annual increase of 0.88 ppm (3.5 GT C/yr) (IPCC 2007). Approximately two-thirds of the total increase in atmospheric CO ₂ is a result of the burning of fossil fuels, with the remainder coming from SOC loss due to land use change (Lal 2004), such as the clearing of forests and the cultivation of land for food production (Fig. 5).

While the carbon released to the atmosphere through deforestation includes carbon emitted from the decomposition of aboveground plant biomass, carbon levels in the soil are also rapidly depleted from the decomposition of SOM. The decomposition of SOM is due to the activity of the microbial decomposer community in the absence of continual rates of carbon input from the growth of forest vegetation, as well as increased soil temperatures that result from warming of the ground once the forest canopy has been removed. Although this soil carbon loss has contributed to increased CO ₂ levels in the atmosphere, it also is an opportunity to store some of this carbon in soil from reforestation.

Despite the much larger size of the oceanic carbon pool relative to the soil carbon pool, the rate of exchange between the atmosphere and the soil is estimated to be higher than that between the atmosphere and the ocean. Current estimates are that carbon inputs from photosynthesis by terrestrial vegetation fixes more carbon than carbon loss through soil respiration, resulting in a soil storage rate of about 3 GT C/yr. Oceanic carbon flux rates suggest oceans store about 2 GT carbon/yr despite occupying a vastly larger proportion of the earth's surface. Although there is interest in increasing oceanic carbon storage rates through large-scale nutrient additions, there is skepticism towards this approach due to the unknown consequences on global nutrient cycles and marine ecosystems (Cullen & Boyd 2008). The goal of increased storage of carbon in soil has received much wider acceptance due to a better understanding of the processes involved in SOC storage, more direct control of these processes through human activities, and the other known ecosystem benefits to be obtained by increasing SOC, including benefits to water quality and increased food security.

Soil carbon sequestration is a process in which CO ₂ is removed from the atmosphere and stored in the soil carbon pool. This process is primarily mediated by plants through photosynthesis, with carbon stored in the form of SOC. In arid and semi-arid climates, soil carbon sequestration can also occur from the conversion of CO ₂ from air found in soil into inorganic forms such as secondary carbonates; however, the rate of inorganic carbon formation is comparatively low (Lal 2008).

Since the industrial revolution, the conversion of natural ecosystems to agricultural use has resulted in the depletion of SOC levels, releasing 50 to 100 GT of carbon from soil into the atmosphere (Lal 2009). This is the combined result of reductions in the amount of plant roots and residues returned to the soil, increased decomposition from soil tillage, and increased soil erosion (Lemus & Lal 2005). Depletion of SOC stocks has created a soil carbon deficit that represents an opportunity to store carbon in soil through a variety of land management approaches. However, various factors impact potential soil carbon change in the future, including climatic controls, historic land use patterns, current land management strategies, and topographic heterogeneity.

Continued increases in atmospheric CO ₂ and global temperatures may have a variety of different consequences for soil carbon inputs via controls on photosynthetic rates and carbon losses through respiration and decomposition. Experimental work has shown that plants growing in elevated CO 2 concentrations fix more carbon through photosynthesis, producing greater biomass (Drake et al. 1997). However, carbon loss may also increase due to increased plant respiration from greater root biomass (Hungate et al. 1997), or from accelerated decomposition of SOM through increased microbial activity (Zak et al. 2000). Likewise, increased temperatures may impact the carbon balance by limiting the availability of water, and thus reducing rates of photosynthesis. Alternatively, when water is not limiting, increased temperatures might increase plant productivity, which will also impact the carbon balance (Maracchi et al. 2005). Increased temperatures may also lead to higher rates of SOM decomposition, which may in turn produce more CO ₂, resulting in positive feedbacks on climate change (Pataki et al. 2003).

At the scale of a watershed or crop field, the carbon sequestration capacity of the soil may be influenced by local controls on ecosystem processes. Processes such as rainfall infiltration, soil erosion and deposition of sediment, and soil temperature can vary on local scales due to landscape heterogeneity - all of which affect carbon input and carbon loss rates (Fig. 6), resulting in differences in SOC contents along topographic gradients (Thompson and Kolka 2005). For example, slope position impacts soil moisture and nutrient levels, with subsequent impacts on the root growth of plants that may have consequences for soil carbon (Ehrenfeld et al. 1992). The combined effects of changes in carbon inputs and losses from land use, land management, and landscape-level effects on carbon input and loss rates result in variation in the carbon sequestration capacity across landscapes.

Carbon sequestration potential may be determined by an understanding of both the historic SOC stocks under natural vegetation prior to conversion to other uses and the influences of those land uses on carbon loss. Land uses and management that reduce carbon inputs or increase losses compared to natural vegetation result in reductions in SOC over time, creating a soil carbon deficit relative to the levels of carbon that previously existed in the soil. This deficit represents an opportunity to store carbon from conversions in land use and management when those changes result in either increased inputs or decreased losses of carbon. For example, reforestation or grassland restoration on a former crop field can reduce the carbon deficit caused from years of agricultural production and sequester carbon through higher root productivity compared to crops. Likewise, the creation of wetlands and ponds can sequester large amounts of carbon because decomposition is greatly reduced in waterlogged soils from lack of oxygen; this can actually result in carbon gains that exceed the deficits resulting from past land use. Other management practices such as irrigation of pasture or rangelands may also increase carbon levels beyond historic SOC stocks if carbon inputs under new management greatly exceed levels under natural conditions. The effect of land management on SOC levels, especially the impacts of management in agricultural settings, is the subject of much current research (Table 1). These changes in soil carbon, however, typically take many decades to occur, making actual measurements of changes in SOC stocks difficult.

SOC is a vital component of soil with important effects on the functioning of terrestrial ecosystems. Storage of SOC results from interactions among the dynamic ecological processes of photosynthesis, decomposition, and soil respiration. Human activities over the course of the last 150 years have led to changes in these processes and consequently to the depletion of SOC and the exacerbation of global climate change. But these human activities also now provide an opportunity for sequestering carbon back into soil. Future warming and elevated CO ₂, patterns of past land use, and land management strategies, along with the physical heterogeneity of landscapes are expected to produce complex patterns of SOC capacity in soil.

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Organic matter is a key component of soil that affects its physical, chemical, and biological properties, contributing greatly to its proper functioning on which human societies depend. Benefits of soil organic matter (SOM) include improvement of soil quality through increased retention of water and nutrients, resulting in greater productivity of plants in natural environments and agricultural settings.

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Yale Environment 306- Soil as Carbon Storehouse: New Weapon in Climate Fight?

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Yale Environment 306- Soil as Carbon Storehouse: New Weapon in Climate Fight?

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Soil as Carbon Storehouse: New Weapon in Climate Fight?

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The degradation of soils from unsustainable agriculture and other development has released billions of tons of carbon into the atmosphere. But new research shows how effective land restoration could play a major role in sequestering CO2 and slowing climate change.

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NOAA's Pacific Marine Environmental Laboratory (PMEL) Director, Dr. Chris Sabine, narrates an educational video on how and why we measure carbon in the ocean.

The Carbon Group at PMEL works to advance our scientific understanding of the ocean carbon cycle and how it is changing over time. PMEL's research includes documenting the evolving state of the ocean carbon chemistry with high quality measurements on ships and autonomous platforms, studying the ocean's role in the global carbon cycle and the processes involved, and investigating how rising atmospheric CO2 and climate change affect the chemistry of the ocean and its marine ecosystems.

PMEL's efforts support NOAA's commitment to improve the Nation's ability to anticipate and respond to climate impacts, and to conserve and manage healthy oceans, coastal ecosystems, and marine resources.

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NOAA's Pacific Marine Environmental Laboratory (PMEL) Director, Dr. Chris Sabine, narrates an educational video on how and why we measure carbon in the ocean. The Carbon Group at PMEL works to advance our scientific understanding of the ocean carbon cycle and how it is changing over time.

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Explore the Carbon Cycle in pre- and post-industrial eras

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NASA- Earth Science Week: Keeping Up With Carbon

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NASA- Earth Science Week: Keeping Up With Carbon

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NASA | Earth Science Week: Keeping Up With Carbon

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Reliable for most scientific topics. But be careful with controversial topics.

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July 5: Fifth of July in New York

1841 - Thomas Cook, the founder of the British travel company Thomas Cook & Son, organised his first excursion, escorting about 500 people from Leicester to Loughborough.

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Twelve original video games, alongside several ports and other spin-offs, were released by Looking Glass Studios, an American video game developer, in its ten years of activity from 1990 to 2000. The first Looking Glass Studios video game was Ultima Underworld: The Stygian Abyss, which was released in 1992 and received widespread critical acclaim and sold nearly 500,000 units. The studio proceeded to develop titles in multiple genres, including role-playing, sports, flight-simulation, and stealth video games. These were primarily published by Origin Systems, Electronic Arts and Eidos Interactive, with three games self-published by Looking Glass Studios. Their products were praised for innovations in video game technology and design. Several of their successes, such as Flight Unlimited and Thief: The Dark Project, sold more than half a million copies each. Its final project, Jane's Attack Squadron, was completed by Mad Doc Software and released by Xicat Interactive in 2002. (Full list...)

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Cirsium palustre, the marsh thistle, is a herbaceous biennial (or often perennial) flowering plant in the family Asteraceae. It is native to Europe, where it is particularly common on damp ground such as marshes, wet fields, moorland and beside streams. In Canada and the northern United States it is an introduced species that has become invasive. It grows in dense thickets that can crowd out slower-growing native plants. Cirsium palustre can reach up to 2 metres (7 ft) in height. The strong stems have few branches and are covered in small spines. In its first year the plant grows as a dense rosette and in subsequent years a candelabra of dark purple or occasionally white flowers, 10-20 millimetres (0.4-0.8 in) with purple-tipped bracts. In the Northern Hemisphere these are produced from June to September. The plant provides an important source of nectar for pollinators. This C. palustre flower was photographed in Niitvälja, Estonia.
Photograph credit: Ivar Leidus

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From Wikipedia, the free encyclopedia July 5 : Fifth of July in New York 1841 - Thomas Cook , the founder of the British travel company Thomas Cook & Son, organised his first excursion, escorting about 500 people from Leicester to Loughborough.