How many calories are contained in the land, air, and sea is a complex question with many variables to consider. At a basic level, the number of calories depends on the types of organisms present and their density within a given area. However, providing an exact calorie count is virtually impossible given the immense diversity and variability of life on Earth. Some quick estimations can be made by looking at the major biomass components of each sphere.
Land
The total biomass on land is estimated to be around 2,000 gigatonnes carbon (Gt C). This includes all plant life such as trees, shrubs, grasses and crops. The calorie content of plants can vary substantially by species. As a rough estimate, 1 gram of dry plant matter contains around 4 Calories. If we assume an average of 4 Calories per gram, the total calories contained in land biomass would be approximately:
2,000 Gt C x (1,000,000,000 tonnes/Gt) x (1,000 g/tonne) x (4 Cal/g) = 8 x 10^18 Calories
So in very rough terms, the total calories contained in land biomass is around 8 x 10^18 Calories. This excludes animal life, which would add substantially more calories.
Air
Estimating the calories in the air is challenging because air itself does not contain energy. However, the total biomass of flying birds, insects and other airborne organisms contains calories. The total global bird biomass is estimated at around 0.1 Gt C. Again assuming 4 Cal/g, this would equate to:
0.1 Gt C x (1,000,000,000 tonnes/Gt) x (1,000 g/tonne) x (4 Cal/g) = 4 x 10^15 Calories
This is likely an underestimate since it excludes insects and other flying creatures. But it gives a very rough sense that the total calories contained in airborne life is on the order of 10^15 Calories.
Sea
The oceans contain a huge diversity of life and account for the majority of Earth’s biomass. The total biomass of marine life is estimated at around 1,000 Gt C. Again using the approximation of 4 Cal/g, the total calories contained in ocean life would be:
1,000 Gt C x (1,000,000,000 tonnes/Gt) x (1,000 g/tonne) x (4 Cal/g) = 4 x 10^18 Calories
This excludes dissolved organic carbon and other forms of non-living biological material which would also contain calories. But it provides a rough estimate of the tremendous amount of energy stored in ocean life.
Calories in Different Environments
While the back-of-the-envelope calculations above provide totals for land, air and sea life, enormous variability exists within each sphere. The concentration of biomass and hence calories can differ greatly depending on the local environment. Here is a more detailed look at calorie differences across ecosystems:
Calories in Different Land Ecosystems
| Ecosystem | Calorie Density* |
|---|---|
| Tropical rainforest | High |
| Temperate forest | Moderate |
| Boreal forest | Low |
| Tropical grassland | High |
| Temperate grassland | Moderate |
| Tundra | Very low |
| Desert | Extremely low |
| Wetland | High |
| Cropland | Very high seasonally |
*Calorie density refers to the amount of calories stored per unit area in each ecosystem type.
Tropical ecosystems such as rainforests contain extremely high densities of plant matter and support an abundance of animal life. They are estimated to contain over 1,500 tons of living material (biomass) per acre. This translates to very high calorie densities.
On the other end of the spectrum, deserts contain very little plant and animal biomass, containing an estimated 10-15 tons per acre. The arctic tundra also supports relatively scant vegetation and low animal densities.
Temperate regions and grasslands exhibit intermediate levels of biomass, containing 100-800 tons of living material per acre. Agricultural lands can seasonally support very high calorie densities in the form of crops.
Calories in Different Marine Ecosystems
| Ecosystem | Calorie Density* |
|---|---|
| Coral reef | Very high |
| Mangrove forest | High |
| Kelp forest | High |
| Seagrass bed | Moderate |
| Estuary | High |
| Continental shelf | Moderate |
| Open ocean | Low |
| Deep sea | Very low |
*Calorie density again refers to the amount of calories per unit area.
In the oceans, coastal regions containing coral reefs, kelp forests, and estuaries contain the highest density of marine life and energy. These areas can host over 2,000 tons of biomass per acre.
Open ocean and deep sea ecosystems contain relatively low densities of organisms by area. But because of the vast size of these ecosystems, they still account for a majority of global marine biomass and energy.
Forms of Calories in Land, Air and Sea
Now that we’ve looked at the overall calorie content of the major spheres and different environments, let’s examine some of the major forms those calories take:
Major Forms of Calories on Land
– Plant matter – includes all living vegetation from grasses to trees, representing most land biomass
– Animal tissue – energy contained in the muscles, organs, and tissue of terrestrial animals
– Dead wood – fallen trees and branches contain calories
– Soil organic matter – decaying material in soils holds calories
– Fungi and microbes – soil and leaf fungi and decomposers contain energy
Major Forms of Calories in the Air
– Bird tissue – energy contained in bird muscle, organs, and tissue
– Insect tissue – calories inside insects including butterflies, mosquitos etc.
– Windborne microbes and fungi – airborne microorganisms contain traces of calories
Major Forms of Calories in the Sea
– Fish tissue – energy stored in fish muscles, organs and tissue
– Phytoplankton – marine algae contain calories and account for about half of ocean biomass
– Zooplankton – small drifting animals harbor significant calories
– Bacteria and microbes – marine bacteria play key roles in ocean food webs
– Corals and marine plankton – sedentary species contain calories and support animal life
– Whale tissue – large amounts of calories in whale muscles, blubber, and organs
– Dead marine snow – sinking organic debris composed of dead organisms and waste
This breakdown shows that most land calories are contained in plant matter, while most marine calories occur as animal and microbial tissue. The air comprises relatively few calories mostly from mobile animal life.
Calorie Transfer Between Land, Air and Sea
While we’ve looked at the calories present in each sphere, it’s important to note that significant calorie transfer occurs between the land, air and sea through natural processes:
– Land plant matter provides calories and nutrition for herbivorous terrestrial animals
– Dead plant material decomposes providing calories that enrich soils
– Birds and insects can transport calories through the air from land to sea
– Fish absorb calories by consuming phytoplankton and zooplankton
– Whales transport tons of calories over long distances through migration
– Rainfall carries dissolved organic matter full of calories from land into the sea
– Microbes decompose dead organisms transferring calories back into the soil or water
– Evaporation and precipitation create a global circulation of calories and nutrients
This constant cycling and movement of calories interconnects the three spheres. The biomass present at a given locale depends on this exchange of energy.
Anthropogenic Effects on Calorie Distribution
While natural processes drive calorie cycling, human activities significantly disrupt and alter calorie distribution within and between Earth’s spheres:
– Deforestation reduces land biomass and terrestrial calorie content
– Fertilizer runoff increases marine algal growth and sea calories
– Overfishing depletes calories stored in fish populations
– Pollution disrupts marine food chains lowering calorie transfer efficiency
– Climate change impacts growth rates and geographic ranges of organisms
– Invasive species can dramatically alter native calorie densities
– Agricultural practices convert natural calories into dense human foods
Humans both intentionally and inadvertently redistribute calories. Our actions have enormous potential to either augment or diminish the calorie content across ecosystems. Careful stewardship is needed to maintain the balance of energy through the spheres.
Conclusion
While rough estimates can be made, quantifying the exact number of calories present on land, in the air, and in the oceans is extremely complex. The immense variability in biomass distribution makes precise calculations virtually impossible. However, we can say that terrestrial ecosystems likely contain trillions more calories than the air, while marine systems contain comparable or greater calories than the land. Within each sphere, huge differences in calorie density reflect differences in climate, productivity, and biodiversity across biomes. Ongoing exchange and transport of calories links the spheres in an interconnected system. As a keystone species, humans have an outsized role in reshaping global calorie budgets. But with thoughtful stewardship, we can maintain the natural flows of energy through the planet.