---------- Forwarded message ----------
Date: 20 Jun 95 03:04:14
Subject: A little data (ecol-econ)
* Xposted: msg originally in ecol-econ.
From Alan McGowen to doug bashford on 14 Jun 95 12:42:59
about: A little data:
Since some would like to see more data, here is a
bit of data I have at hand that all readers should
* * *
Blair Sandler asked:
> <What is NPP?>
Net primary production. It's the photosynthetic production
of plants minus what they use for their own life processes
-- so it's the amount of food left over for everything else.
Think of it as the GNP of an ecosystem.
Let's look at some numbers.
(1 Pg = 10^15g)
Total terrestrial NPP ["terrestrial" means "on land",
i.e. this doesn't include marine NPP.] 132
Consumed by humans 0.8
Consumed by domestic animals 2.2
Wood used by humans 2.4
(4% of total)
Croplands (1) 15
Converted pastures (1) 10
Tree plantations (1) 2.6
Human-occupied lands (1) 0.4
Consumed from little-managed
ecosystems (2) 3
Land clearing 10
(31% of total)
NPP lost to human activity
Decreased NPP of cropland vs.
natural systems (3) 10
Human-occupied areas 2.6
(together with the NPP dominated,
39% of total potential NPP)
(1) This includes the total NPP of wholly human-dominated
(2) This category includes wood harvested and forage
consumed by domestic animals on little-managed systems,
and anthropogenic fires.
(3) This accounts for a decrease (on average) in the NPP
of crop systems compared to the natural systems they
replace, due primarily to the substitution of annuals for
perennials. If we follow Olson et al. (1983) and assume
that cropland NPP is equal to or above that of natural
systems, this component of loss dissappears but is
replaced by an equivalent amount of cropland NPP
dominated by humanity.
[From Vitousek et al., 1986, quoted in Vitousek, 1994.]
"NPP dominated" refers to NPP of human-dominated systems.
These are areas that function in wholly different ways
as a result of human use and human-caused land use change.
Olson, J. S., J. A. Watts, and A. J. Allison. 1983.
Carbon in live vegetation of major world ecosystems.
Oak Ridge National Laboratory, Oak Ridge, Tennessee,
Vitousek, P. M., P. R. Ehrlich, A. H. Ehrlich, and P. A.
Matson. 1986. Human appropriation of the products of
photosynthesis. BioScience 36:368-373.
Vitousek, P. M. 1994. Beyond global warming: ecology and
global change (MacArthur award lecture). Ecology 75(7),
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... False economic assumptions are the root of all social problems.