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Re: Ecological Economics and Entropy
Steinn Sigurdsson wrote:
> Joel Cohen's article in Science July 21 1995 discusses
> the problem of defining human carrying capacity.
> The discussion is (apparently) elaborated in his
> recent (reputadly good) book.
>
> Jay Hanson's "definitions" are no more reliable for
> carrying capacity than they are for thermodynamics.
It is a problem to define human carrying capacity,
so it cant be done? Is that what passes for logic
at Cambridge?
It never fails to amaze me that there are so many
idiots in universities. What do you do at Cambridge?
Sweep up?
Even the intellectually challenged should be able to
get through the following post. Give it a try, let us
know how it comes out.
============================================================
Investing in Natural Capital:
The Ecological Approach to Sustainability
from the International Society for Ecological Economics
CARRYING CAPACITY REVISITED
Ecologists define "carrying capacity" as the population of a
given species that be supported indefinitely in a defined
habitat without permanently damaging the ecosystem upon which
it is dependent. However, because of our culturally variable
technology, different consumption patterns, and trade, a
simple territorially-bounded head-count cannot apply to human
beings. Human carrying capacity must be interpreted as the
maximum rate of resource consumption and waste discharge that
can be sustained indefinitely without progressively impairing
the functional integrity and productivity of relevant
ecosystems wherever the latter may be. The corresponding
human population is a function of per capita rates of material
consumption and waste output or net productivity divided by
per capita demand (Rees 1990). This formulation is a simple
restatement of Hardin's (1991) "Third Law of Human Ecology":
(Total human impact on the ecosphere) =
(Population) x (Per capita impact).
Early versions of this law date from Ehrlich and Holdren who
also recognized that human impact is a product of population,
affluence (consumption), and technology: I = PAT (Ehrlich and
Holdren 1971; Holdren and Ehrlich 1974). The important point
here is that a given rate of resource throughput can support
fewer people well or greater numbers at subsistence levels.
Now the inverse of traditional carrying capacity provides an
estimate of natural capital requirements in terms of
productive landscape. Rather than asking what population a
particular region can support sustainably, the question
becomes: How much productive land and water area in various
ecosystems is required to support the region's population
indefinitely at current consumption levels?
Our preliminary data for developed regions suggest that per
capita primary consumption of food, wood products, fuel, and
waste- processing capacity co-opts on a continuous basis up to
several hectares of productive ecosystem -- the exact amount
depends on the average levels of consumption (i.e., material
throughput). This average per capita "personal planetoid" can
be used to estimate the total area required to maintain any
given population. W call this aggregate area the relevant
community's total "ecological footprint' (see Figure 20.2) on
the earth (Rees 1992).
This approach reveals that the land "consumed" by urban
regions is typically at least an order of magnitude greater
than that contained within the usual political boundaries or
the associated built-up area. However brilliant its economic
star, every city is an entropic black hole drawing on the
concentrated material resources and low-entropy production of
a vast and scattered hinterland many times the size of the
city itself. Borrowing from Vitousek et al. (1986), we say
that high density settlements "appropriate" carrying capacity
>from all over the globe, as well as from the past and the
future (Wackernagel 1991).
The Vancouver-Lower Fraser Valley Region of British Columbia,
Canada, serves as an example. For simplicity's sake consider
the region's ecological use of forested and arable land for
domestic food, forest products, and fossil energy consumption
alone: assuming an average Canadian diet and current
management practices, 1.1 ha of land per capita is required
for food production, 0.5 ha for forest products, and 3.5 ha
would be required to produce the biomass energy (ethanol)
equivalent of current per capita fossil energy consumption.
(Alternatively, a comparable area of temperate forest is
required exclusively to assimilate current per capita C02
emissions (see "Calculating the Ecological Footprint").
Thus, to support just their food and fossil fuel consumption,
the region's 1.7 million people require, conservatively, 8.7
million ha of land in continuous production. The valley,
however, is only about 400,000 ha. Our regional population
therefore "imports" the productive capacity of at least 22
times as much land to support its consumer lifestyles as it
actually occupies (see Figure 20.3). At about 425 people/km2
the population density of the valley is comparable to that of
the Netherlands (442 people/km2) [p.p. 369-371]
Even with generally lower per capita consumption, European
countries live far beyond their ecological means. For
example, the Netherlands' population (see Figure 20,4)
consumes the output of at least 14 times as much productive
land as is contained within its own political boundaries
(approximately 110,000 km2 for food and forestry products and
360,00 km2 for energy)(basic data from WRI 1992).8 [p. 374]
PUBLISHED BY:
The International Society for Ecological Economics and
Island Press -- 1994 http://www.islandpress.com
1-800-828-1302 or 1-707-983-6432 Fax 1-707-983-6164
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