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Sustainability assessment

The ecological sustainability of the South West

Biocapacity

Biocapacity is a measure of the biological productivity in an area. It is an aggregate of the productivity of various ecosystems within the area, for example, arable or crop land, pasture, forest and bioproductive sea, built or degraded land. Biocapacity is dependent not only on natural conditions but also on prevailing farming and forestry practices.

Bioproductivity

Bioproductivity is the ability of a piece of land to produce biomass, which is the weight (or estimated equivalent) of organic matter, including animals, plants and micro-organisms (living or dead) above or below the soil surface. Different ecosystems will have different levels of bioproductivity.

Earthshare

The earthshare is the average amount of global resources available per person. To calculate earthshare, the total available bioproductive land and sea area of the planet is divided equally among the current global population. It is estimated that the current earthshare is 1.9 gha (Loh, 2002). If everyone lived within their earthshare, we would be ecologically sustainable at a global level.

Yield

Rate of production, for example agricultural production per hectare of crop.

An ecological footprint measures the demand for natural resources. By comparing this demand with available supply it is possible to estimate ecological sustainability. This supply is referred to as 'biocapacity'.

per person biocapacity

Where:

  • L = the area of that land type
  • Y = the bioproductivity or yield of that area type

Biocapacity can be derived at any geographical scale - it just depends on the boundaries chosen. For the purposes of sustainability assessments, biocapacity is expressed in global hectares (gha) to ensure consistency with the ecological footprint.

The South West's biological capacity

The bioproductivity of the different area types identified in the South West was assessed to derive the region's biocapacity, as shown in Table 11.

Table 11
The South West's biocapacity
 
Area type Total biocapacity (gha) Biocapacity per person (gha) % of total biocapacity
Total biocapacity 9,438,071 1.91 100%
of which…  
Arable 2,854,134 0.58 30%
Pasture 2,632,634 0.53 28%
Built land* 1,292,177 0.26 14%
Forest 893,970 0.18 9%
Sea** 1,765,156 0.36 19%
* Built land is included to illustrate 'potential bioproductivity'.
** Average per person UK data from the National Footprint Accounts (Redefining Progress, 2002) was used to derive this figure.
Note: Totals may differ due to rounding.

The South West's biocapacity is 1.91 gha per person. If the same principles are applied to the whole world, the biocapacity per person, often referred to as the 'average earthshare', would be 1.9 gha (Redefining Progress, 2002). The South West's biocapacity is virtually equivalent to the average earthshare because the region has higher than global average bioproductivity and higher than global average population density.

The ecological footprint can be compared with biocapacity derived at either the global, national or regional level. Comparing a South West resident's ecological footprint (5.56 gha) with the region's biocapacity per person (1.91 gha) indicates whether the population is living within the means of its regional boundaries - or not. The figures show that at a regional level, demand for natural resources is greater than supply. Alternatively, it is possible, and some would argue more desirable, to compare the ecological footprint with globally available biocapacity as an indication of whether the South West's population is living within the environmental and equitable means of our planet. This comparison is shown in Table 12.

Table 12
Comparing a South West resident's ecological footprint with regional, national and global biocapacity, in 2001
 
  Global hectares per person
South West resident's ecological footprint 5.56
South West's biocapacity 1.91
UK's biocapacity 1.64
The world's biocapacity (earthshare) 1.90
 

If everyone on the planet consumed as much as an average South West resident, 3 Earths would be needed to support current global resource consumption.