Ecological Footprint and Biocapacity Accounting

Ecological Footprint analysis examines the size of society's metabolism with a specific research question: how much of the regenerative capacity of the biosphere is being occupied by human activities? To answer this question, footprint analysis measures how much biologically productive land and water area an individual, a city, a country, a region, or humanity uses to produce the resources it consumes and to absorb the waste it generates, using prevailing technology and resource management schemes.

This demand can be compared with supply, or bioca-pacity, the total available biologically productive surface of the planet. The common unit used for this analysis, as the term 'footprint' suggests, is a global hectare, one hectare of land or sea with world-average biological productivity.

Calculating Demand: Footprint

At present, human demands on ecosystems, a population's footprint, are translated into demands for six major land types - cropland, grazing land, fishing grounds, forest, built-up land, and 'carbon land' (Table 1). The first four

Table 1 Major land types in Ecological Footprint and biocapacity accounting. The biocapacity associated with emissions of carbon dioxide is represented by forest land

Ecological Footprint

Biocapacity

Cropland

Cropland

Grazing land

Grazing area

Fishing grounds

Fishing grounds

Forest

Forest

Built-up land

Built-up land

'Carbon land'

NA

From Global Footprint Network (2005) National Footprint Accounts, 2005 edition. Available at http://www.footprintnetwork.org.

From Global Footprint Network (2005) National Footprint Accounts, 2005 edition. Available at http://www.footprintnetwork.org.

of these land types produce food, fiber, and timber products for human consumption. These products may be consumed directly or processed further before final consumption. Regardless of the forms they eventually take within society, however, all products produced from these four land types can be translated, through the use ofyields (annual tonnes per hectare) and conversion factors (tonnes of processed product per tonnes of raw material), back into the amount of area required to produce the products. This land and water area can be located anywhere on the planet.

The fifth land type, built-up land, represents the area required for the physical infrastructure associated with human society, such as cities and roads. The sixth land type, carbon land, represents the amount of biologically productive space required to absorb one of the human economy's most significant waste products: carbon dioxide. This footprint is currently calculated as the amount of forested area required to sequester a given amount of carbon dioxide, effectively removing it from the atmosphere, after accounting for absorption by the oceans.

This approach of translating fossil fuel use into bioproductive area does not suggest that afforestation or other types of biological sequestration are the solution to reducing atmospheric carbon dioxide concentrations. These measures do show, however, how much larger the biosphere would need to be to stabilize carbon dioxide concentrations in the atmosphere without further human intervention. The 2005 Edition of the National Footprint Accounts, for example, calculates that in 2002 the release of one tonne of carbon dioxide per year has a footprint of approximately 0.27 global hectares. Other human-supported methods exist for sequestering carbon dioxide, and the use of these technologies will be reflected in a decrease in the energy footprint as they are brought on line. Similarly, the introduction of renewable energy technologies with lower carbon intensities will also lead to a reduced carbon footprint.

Calculating Supply: Biocapacity

Human demand, or footprint, can be compared to the total availability of biologically productive land and sea, or biocapacity. Biocapacity is currently measured in five major land types (Table 1), analogous to the six land types of footprint with the exception of 'carbon land' (the regenerative capacity available for sequestering carbon dioxide emissions is included in the other major land types).

Globally, footprint analysis identifies, for 2002, approximately 11.2 billion hectares of biologically productive land and sea that can provide economically useful concentrations of renewable resources. These 11.2 billion hectares cover just under one quarter of the planet's surface and include 1.5 billion hectares of cropland, 3.5 billion hectares of grazing land, 3.6 billion hectares of forest, 2.3 billion hectares of marine and inland fisheries, and 0.2 billion hectares of built-up land.

These areas concentrate the bulk of the biosphere's regenerative capacity. There are not yet concrete estimates of precisely how much of the total usable annual biomass generation or net primary production is concentrated on these 11.2 billion hectares, but the number is likely not lower than 80% or possibly 90%. While the remaining areas of the planet are also biologically active, such as the deep oceans or deserts, their renewable resources are not concentrated enough to be a significant addition to the overall biocapacity.

Many materials and pollutants place demands on the biosphere primarily by reducing the ability of ecosystems to provide goods and services, which leads to a loss in biocapacity. Toxics, heavy metals, and other persistent pollutants fall into this category. The amount of bioproductive area required to mine mercury, for example, is vanishingly small compared to the extent of the ecosystems that this metal affects. Similarly, the area required to absorb this product is an undefined quantity, as ecosystems do not have a well-defined or understood ability to assimilate this metal naturally. As a result, the impacts of mercury, as well as other toxics, do not appear primarily in the material's footprint but rather in the widespread loss of biocapacity that it can cause when released widely into the environment.

The Common Unit: Global Hectares

Given the widely varying scope of human demands, and the wide variety of ecosystems available on the planet, any aggregate analysis or indicator requires a common metric for comparison. Ecological Footprint accounts compare different types of footprints to each other and to available biocapacity using a global hectare, defined as a hectare with world-average ecological productivity of the 11.2 billion bioproductive hectares on Earth.

In the context of global hectares, biological productivity does not refer to a rate of biomass production, such as net primary production (NPP). Rather, productivity is the potential to achieve maximum yields of products considered useful for human purposes. As a result, one hectare of highly productive land (e.g., cropland) is equal to more global hectares than one hectare of less productive land (e.g., pasture). Global hectares are normalized so that the number of actual hectares of biologically productive land and sea on the planet is equal to the total worldwide budget of global hectares in any given year.

What products are useful is defined in any year by the types of products that are actually extracted from global ecosystems. Useful yields, and hence total biocapacity, will increase if largely unharvested ecosystem products (e.g., tree bark) are extracted on a large scale in the future.

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Responses

  • Luam
    What is bicapacity accounting?
    2 years ago
  • Alisha Henderson
    What is biocapacity accounting?
    2 years ago
  • Gorbulas Gardner
    What does biocapacity referred to?
    2 years ago

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