Where Is The Biomass?

Biomass refers to the total mass of all living organisms in a given area or ecosystem. It includes plants, animals, bacteria, fungi and other organisms. Biomass is an important measure of the health and productivity of an ecosystem. The amount and distribution of biomass plays a key role in global carbon and nutrient cycles.

Most biomass on Earth is found in plants. Plants produce biomass through photosynthesis, converting sunlight, water and carbon dioxide into energy and plant matter. Biomass can be measured for a given habitat, biome or the entire biosphere. Understanding where biomass is located and how it changes over time provides critical insights into the functioning of ecosystems and their role in climate change.

In this article, we will examine the distribution of biomass across different regions and habitats on Earth. We will look at terrestrial, oceanic and soil biomass. We will also discuss methods for measuring and mapping biomass globally.

Terrestrial Biomass

The majority of biomass on land is contained in forests. Trees contain large amounts of woody biomass in their trunks, branches, stems, and roots. The total amount of biomass contained in forests globally is estimated to be over 80% of all biomass on land. After forests, grasslands contain the next largest amount of biomass. Grasses and other herbaceous plants contain biomass largely in their stems and leaves. Croplands also contain significant biomass in cultivated grasses, shrubs, and trees. Agricultural biomass includes residues left after harvesting crops, manure, and purpose-grown energy crops. On land, biomass is distributed unevenly based on climate, soil conditions, and human land use. Tropical and temperate forests tend to contain more biomass than boreal forests. Grassy savannas and plains contain more biomass than arid scrublands or deserts.

Oceanic Biomass

The oceans contain a significant amount of the planet’s biomass, primarily in the form of phytoplankton. Phytoplankton are microscopic, photosynthetic organisms that live suspended in the upper layers of the ocean. While individually tiny, phytoplankton exist in huge numbers and are the foundation of the marine food web.

Phytoplankton biomass is estimated at between 1 and 10 billion tons of carbon. Phytoplankton absorb large amounts of CO2 through photosynthesis and provide over half of the oxygen in the atmosphere. In addition to phytoplankton, marine algae form an important source of biomass along coastal regions and throughout the ocean. Macroalgae, like giant kelp and sargassum, provide habitat and food for many marine organisms. There are also vast meadows of seagrass in coastal areas which are highly productive ecosystems.

In total, scientists estimate that the biomass of marine plants equals 3-6 times the total global biomass of terrestrial plants. The oceans play a vital role in global biomass production and distribution.

Soil Biomass

Soil biomass refers to all the living organic matter in the soil, including microorganisms, earthworms, plant roots, and small animals. The soil biomass plays a vital role in soil health and productivity. The major components of soil biomass include:

Microorganisms – Bacteria and fungi make up the majority of soil microorganisms. They drive key nutrient cycles like the carbon and nitrogen cycles. Microbes decompose organic matter, making nutrients available for plant uptake. They also form symbiotic associations with plant roots.

Earthworms – Earthworms are essential ecosystem engineers. As they burrow through the soil, they aerate the soil, improve drainage and water infiltration. Earthworm castings are rich in nutrients. Their burrowing mixes the soil layers.

Plant roots – Living roots and root exudates are an important source of organic carbon for microbes. Roots hold soil in place preventing erosion. The rhizosphere is a hotspot of microbial activity.

Other soil fauna like nematodes, arthropods and small mammals are also part of the soil biomass. Soil biomass is concentrated near the surface but extends meters deep into the soil profile. The size and activity of the soil biomass depends on climate, soil type, and land management practices.

Regional Differences

Biomass distribution varies significantly across different geographic regions and biomes. Tropical rainforests, such as the Amazon, contain some of the highest biomass densities on Earth. The warm climate and abundant precipitation in rainforests support dense vegetation growth and high animal populations.

In contrast, deserts and other arid regions contain very little biomass due to limited water availability. Grasslands and savannas have intermediate levels of biomass, supported by seasonal precipitation. Boreal forests in high latitudes also store significant carbon in their vegetation and soils.

The distribution of biomass depends heavily on precipitation, temperature, soil fertility, and other local environmental factors. Latitude is also an important determinant of biomass, as tropical regions receive more solar radiation and support more plant growth. Higher biomass levels are sustained near the equator, decreasing towards the poles.

Overall, it is estimated that South America and Africa have the highest biomass densities globally based on their extensive tropical forests and savannas. Meanwhile, northern latitude regions like the tundra have sparser vegetation and lower biomass stocks. Understanding these regional patterns can inform estimates of carbon storage and habitat resources.

Measuring Biomass

There are several techniques used for measuring and estimating biomass across different environments and scales. These include:

Direct harvesting: This involves physically collecting all plant material from a known area, drying it, and weighing it to determine dry biomass per unit area. This is labor intensive but provides an accurate, direct measurement of biomass.

Allometric equations: These use statistical relationships between easy-to-measure tree properties like diameter and height to estimate total aboveground biomass for individual trees. These individual tree biomass estimates can be summed to calculate stand-level biomass.

Remote sensing: Satellite data and aerial surveys can be used to measure canopy cover, vegetation indices, tree height, and other variables. When combined with ground-truthing data, these can be used to estimate biomass over large regions.

Modeling: Computer models can integrate data on climate, soil, land-use, and ecological principles to estimate current biomass stocks and project future dynamics.

Each method has advantages and disadvantages in terms of accuracy, resolution, and feasibility. Using multiple, complementary approaches provides the most complete understanding of biomass distribution.

Biomass Mapping

There have been increasing efforts in recent years to map the distribution of biomass globally. This involves using satellite data, field measurements, and modeling to estimate the amount of living organic matter in different ecosystems around the world. Mapping biomass has important applications for understanding the global carbon cycle, biodiversity, and vegetation productivity.

One major effort is the creation of biomass maps by NASA and other organizations that quantify aboveground biomass. This involves analyzing satellite imagery from instruments like lidar that can measure vegetation height and structure to estimate biomass density. These maps provide insights into how much carbon is stored in forests and other ecosystems.

There are challenges involved in biomass mapping, however. Ground measurements of biomass are limited, making it difficult to validate maps. Biomass levels differ depending on factors like seasonal variation, disturbance history, and soil conditions, requiring careful modeling. And remote sensing methods can underestimate biomass in dense, multilayered forests. There are also gaps in consistently mapping belowground biomass stored in roots.

As remote sensing capabilities improve and field data collection expands, biomass mapping is becoming more detailed and accurate. This will help in monitoring changes in biomass over time and directing conservation efforts to high-biomass regions important for carbon storage.

Changing Biomass

Human activity and climate change are having significant impacts on global biomass. Deforestation, land use changes, and the burning of fossil fuels have all contributed to losses in terrestrial biomass in many regions. It’s estimated that land use changes between 1700-2000 resulted in a net loss of 190 billion tons of carbon from vegetation biomass and soils. Tropical regions like the Amazon have been especially impacted, with losses in forest biomass due to factors like logging and slash and burn agriculture.

In addition to direct human impacts, climate change driven events like droughts, wildfires, insect outbreaks, and storms have also depleted biomass in many ecosystems. Models predict these impacts will accelerate in the future, with one estimate projecting a 15% loss in global terrestrial biomass by 2100 if high carbon emission scenarios play out. Climate change is also impacting ocean biomass, with warming waters and acidification threatening ecosystems like coral reefs that support rich assemblages of marine life.

While climate change is reducing biomass in some regions, other areas may see increases in plant growth and ecosystem carbon storage. Higher CO2 levels can stimulate plant productivity and increased temperatures open up new suitable habitat at high latitudes. However, the potential benefits are small compared to projected losses in vulnerable tropical and temperate ecosystems. Sustainable management practices and habitat conservation will be crucial for minimizing biomass declines.

Biomass Applications

Biomass has numerous practical applications and uses in our everyday lives. Here are some examples:

Energy Production

Biomass can be used to generate renewable energy through direct combustion, where it is burned to produce heat, as well as through conversion processes like gasification and anaerobic digestion to produce biogas. Common biomass feedstocks used for energy production include wood, agricultural residues, and organic municipal solid waste.

Materials and Chemicals

Biomass can be used to produce a wide variety of materials and chemicals that would otherwise be made from fossil fuels. For example, sugarcane and corn starch are used to manufacture bioplastics. Cellulosic biomass can also be broken down into sugars and fermented to produce biofuels like ethanol.

Soil Health

Adding organic matter like compost, manure, or crop residues to soil helps improve its physical, chemical, and biological properties. This soil biomass promotes nutrient cycling, water retention, and overall soil fertility and crop productivity.

Habitat and Biodiversity

Biomass in the form of plants, trees, and aquatic vegetation provides habitat structure and food resources that support a diversity of organisms and ecosystems. Maintaining these biomass resources is key to conservation efforts.

Conclusion

In conclusion, understanding the distribution of biomass across the planet is crucial for several reasons. First, biomass represents an important carbon sink that helps regulate Earth’s climate and mitigate climate change. Mapping biomass highlights regions where carbon storage may be vulnerable or could be enhanced through conservation or restoration efforts. Second, quantified biomass resources guide sustainable use for food, fuel, and industrial materials. As the human population grows, optimizing use of biomass will be essential. Third, changes in biomass over time provide insight into ecosystem health and productivity. Declining vegetation biomass may signal degradation, whereas increases may indicate recovery. Evaluating these trends informs policy aimed at protecting ecosystems. Finally, advancing biomass mapping technologies open up new possibilities for monitoring biodiversity, habitat quality, and ecological changes occurring globally. Comprehensive biomass data will be invaluable to humanity as we work toward solutions to pressing environmental challenges.