Sustainable Development Figures& Tentative Projections
(John Davenport, spring 2013)
I. Questions:
How near are we to the carrying capacities of different parts/aspects of the biosphere on Earth?
How much is our use of various environment resources likely to increase during the 21st century?
Are the 'doomsayers' since Donella Meadows (Beyond the Limits) correct or not?
The Endowment Model: environmental capital or "principal" vs "interest" (annual yield).
-- how much of the annual yield are we taking?
-- in what ways are we directly reducing the principal, and thus lowering annual yields?
Limitations in accessible information:
These two sorts of impacts are often not distinguished in the available literatures.
Instructors from outside science teaching environmental topics find it hard to dig into this data.
Much of the available data on which college courses rely is from year 2000, or early 1990s.
However, the recently released Geo-5 reports include more recent data.
Components of Human Footprint (one way of aggregating different impacts):
 Green growth on land used or displaced (by harvesting, grazing, building on)
 Fish from shallow seas (mostly for eating or feeding to livestock)
 Accessible freshwater runoff used (for domestic consumption, irrigation, industry etc)
 Classical pollution absorption and waste processing (in land, watershed, oceans)
 Carbon dioxide, methane, and other greenhouse gases
Does not include fresh water and impacts of toxic substances (hard to express in g-hectares).
Most of the following only concerns our footprint on land and shallow seas; Wilson and the
Footprint network include the costs of warming due to carbon in their calculations.
II. Commonly used sources: Wilson's Figures (from 2002) for land, seas, and carbon:
Edward Wilson says that the average ecological footprint per capita for the entire human race =
2.1 hectare1 of productive land & seas per person. A hectare is 100meters2 or 2.471 acres. When
multiplied by 6 billion in 2002, that is a total footprint of 12.6 billion global hectares in 2002.
1
Edward Wilson, The Future of Life, p.23.
But what are the total amounts of productive land and seas (or ecological capacity) according to
Wilson? This is not totally clear from his book, but he says that if everyone on Earth had the same
ecological footprint as an American in 2002 (9.6 hectares) this would be five times the available
hectares on the planet. And in 2002, he assumes a population of roughly 6 billion. So this implies:
9.6 x 6 billion = 57.6 billion / 5 = 11.5 billion hectares of total productive land and shallow seas
in one earth. That agrees fairly well with a number of web sources too.
This explains Wilson’s claim that in 2002 we were already using more than the total available
productive land and seas that Earth has. This might seem to be impossible, but (a) it includes
degrading the principal base of the biosphere, rather than the biological “interest” on 11.5 billion
hectares, and (b)the indirect impact of carbon release from fossil fuels. Carbon accounts for just
under 44% of per person footprint, or 0.918 hectares pp out of 2.1 pp in Wilson’s 2002 analysis.
Global Footprint Network Figures: This derivation from Wilson agrees fairly well with the
claim in the Global Footprint Network Ecological Footprint Atlas 2010, which offers their most
current estimates: "In 2007, the area of biologically productive land and water on Earth was
approximately 11.9 billion hectares" (p.13).2 The GFN report also offers this useful breakdown:
A "global hectares,"
again, are areas of
average productivity
in each category.
For example, cropland
is more productive
than an average
hectare of productive
land/seas on Earth.
The total carrying
capacity estimates
were a little lower
when Wilson wrote.
The early Global Footprint Network figures derived from work by Wackernagel, Wermer, and
Goldfinger (WWG for short),3 who originally divided the productive hectares as follows:
9 billion g-hect.
Productive lands of all kinds
2.2 billion g-hect.
Seas (mostly shallow seas with abundant fish)
--------------------------------------------------------------------------------11.1 billion hectares Total available on Earth
2
http://www.footprintnetwork.org/images/uploads/Ecological_Footprint_Atlas_2010.pdf
Wackernagel, Wermer, and Goldfinger, "Introduction to the Ecological Footprint" (March, 2007), entry in
Internet Encyclopedia of Ecological Economics (Global Footprint Network), available online in pdf. This draws on a
book published by Wackernagel and Rees and Wackernagel’s 2002 dissertation. Wackernagel is President of GFN.
3
The current estimates are obviously a little more optimistic at 11.9 billion g-hectares, and this is
the figure I will use in our projections.
The GFN website offers many useful figures. Its current overview graphs estimate that by 2008we
use over 1.5 earths worth of land and seas, up from 1.4 in 2005:
Their downloadable excel chart also shows a footprint of 2.7 global hectares per person(on
average) in 2007; the same figure is cited in the Ecological Footprint Atlas 2010 (p.18).
--Given 6.7 billion people in 2007, these figures imply a total human footprint of 18.09 billion ghectares, which explains the claim that in 2007 we were using 150% of current biocapacity.
Per-Person footprint: In 2003, the GFN webpage showed an average global footprint per person
of 2.25 hectares–closer to the figure that Wilson used(but their webpage no longer shows this
kind of chart, probably because the historical per capita estimates keep being revised up):
If we extend the line to 2.7
g-hectares per person in 2007
it looks like per capita footprint
has been rising sharply in recent
years. And this may be correct.
1.7
____
|
2007
However, the Footprint Atlas
2010 explains revisions in their
methods that have moved the
total footprint line up a bit
across all recent years. So 2.7 pp
in 2007 may not be that much
more than the revised 2003
figure. Note the orange line for
pp. biocapacity. It agrees with
the 2007 figures which give us
11.9 billion g-hectares of total
carrying capacity. 11.9 billion / 6.7 billion people = 1.776 g-hectares per person of biocapacity.
The WWF "Living Planet Report 2012" provides an updated & disaggregated pp footprint chart
(derived from GFN data -- but it is not easy to see where). Their charts also show howpp footprint
is sensitive to economic ups and downs in richer nations because of their high share of total world
footprint. Notice the dips in the mid 70s, early 80s, and again in 2008:
But this implies that the
dark green line for
wealthy nations has
probably gone back up
since 2008.
Developing economies
also have rising total
production + consumption
(Geo-5 p.11). But given
their larger increases in
population, their p-person
footprint is rising little.
-- The black line = world biocapacity per person = about 1.8 g-hectares pp. (the figure given in
the WWF full Living Planet 2012 report, p.12). This is just a bit more optimistic than the 1.776 pp
estimate in the 2003 report. However it may have fallen further pp since then, because this figure
of 1.8 x 7 billion people = almost 13 billion g-hectares (which is more than we really have).
-- In both charts, the biocapacity line goes down as population goes up – but this is because it is a
per person figure. So it does not give us an accurate estimate of any serious loss of carrying
capacity in absolute terms (e.g. from deforestation, desertification, salination of soils).4
For a total world average per person footprint trend line (combining rich and poorer nations), we
need this chart from the WWF "Living Planet Report 2012" (p.40):
Notice here that
this pp footprint a
did bend back up
in 2003 to 2008.
Given the 2008
economic crash
and recovery
since, it may be
about back where
it was, or a little
higher overall.
4
Note that given a population of 6.3 billion people in 2003, the superceded GFN chart implies a per capita
capacity of 1.78 hectares in 2003, which implies a total available resource of 11.2 billion hectares. This agrees well
with our deduction from Wilson. These figures are cited in a European Commission report of 2006.
So what about now? Suppose we roll forward the Global Footprint Network figures to today:
-- total world population is now a little over 7 billion people in 2012.
-- I will assume conservatively that total average pp. footprint has not increased since 2008. It will
remain around 2.7 g-hectares per capita in my projections.
That yields a total human footprint in 2012 of around 18.9 billion g-hectares of productive land
and shallow seas now appropriated directly or indirectly (including productive use foregone and
land used for waste absorption and CO2 sinks)= about 63% over sustainable footprint.
Carbon Footprint inclusion. As noted for Wilson, this is possible only because Global Footprint
Network includes the environmental impact of carbon release (unfortunately they do not yet add
in other significant greenhouse gases like methane, so their calculated carbon footprint is less than
total greenhouse gas footprint). The GFNEcological Footprint Atlas 2010 includes this chart
(p.18) that shows how much of the total footprint consists in the land and seas that would be
required to absorb our greenhouse gases:
Remember that on
this chart, the line at
1 = 1 Earth
biocapacity of 11.9
billion g-hectares.
That was the total
world footprint in
about 1976.Clearly
energy use via fossil
fuels drives most of
this growth. Noncarbon footprint has
expanded only about
18% since 1961.
By contrast, total human footprint increased
over 63% from 1961 to 2007.
And we can see on this chart that most of the
growth in world energy usage is coming from
developing nations with high population
growth as well.
Unfortunately most of this comes from usage
of fossil fuels, as we see in the next chart. Thus
greenhouse gas footprint is the fast-rising
factor, with non-carbon footprint rising more
slowly over time.
And these increases in global energy usage are closely correlated with world GDP growth (notice
the small dip in 2008 when world GDP contracted a bit). Thus much of the footprint increase
that popular environmental authors project comes from growth in use of fossil fuels.
-- For ex., Walter Dodds says (citing a 2007 paper by Dietz, Rosa, and York) that "the human
footprint will increase by about 33% in the next decade" -- but most of this would be carbon.
However, there are problems with this carbon component of the GFN model.
 The trouble with greenhouse gas footprint in general is that it is so hard to project what the
ultimate effects of warming will be on the parts of the biosphere.
 It seems very likely that there will be many harmful effects that imply a net reduction in the
principal base (and thus carrying capacity) of different ecosystems, for example when rainfall
in reduced on croplands or river flow reduced when glaciers have retreated. But reductions in
the principal of a fund are not well modeled as spending a percentage of its annual yield.
 And it is controversial to include these impacts in assessment of sustainability, especially on
the GFN approach that just adds in the amount of land and seas needed to absorb the
greenhouse gases. This does not reflect what will actually happen to the biosphere from
warming. Yet the other elements of footprint are unimpeachable to warming skeptics.
Thus it is more conservative to start with non-carbon (non-greenhouse) footprint and project
increases in these components. Estimates of greenhouse impact can be added back in later.
Non-Greenhouse Footprint: Since a little more than half of total footprint in GFN chart is in
carbon waste impact, taking this component out of the 18.9 billion figure projected for 2012
leaves a 9.3 billion g-hectare non-carbon footprint in 2012.
-- That is over 78% of the available 11.9 billion g-hectares, even leaving warming out entirely.
-- And that is about 1.33 g-hectares per person of footprint.
The big questions for the future are then
1. how much more productive can we make available land and seas (to increase total number of
g-hectares) by more efficient extraction of goods and services from the same capital base?
2. will our non-greenhouse footprint be over 100% of available annual yield by peak population,
or close enough to this that most remaining wilderness and biodiversity is lost?
3. how much will our farming, grazing, logging, and building erode the principal of various parts
of biosphere by then – includes sprawl, salination of soil, soil erosion etc?
4. and how much will global warming erode the productive biocapacity of the biosphere, further
subtracting from the principal base?
First, though, we should check the non-greenhouse footprint figures against another source.
IV. Comparison with Stuart Pimm's figures(from 2001) for land
and shallow seas:
Stuart Pimm's accounting of the Earth leaves carbon footprint aside
and focuses on direct and indirect appropriation of the annual growth
yield on land and in productive/shallow seas.
 His initial total for available productive land is roughly 130
million square kilometers,5 or 13 billion hectares,6 though it
obviously varies enormously in productivity between regions. He
notes that only 100 million km2 can produce much,7 so we can
adjust his land total to something like 10 billion hectares.
 If we assume 2.2 billion hectares of productive shallow seas
(following WWG above) this brings his total for land and seas up
to 12.2 billion hectares, which is slightly higher or a bit more
optimistic than the new Global Footprint Network figure of 11.9 billion.
 However, this may be partly because their unit is "global hectares," and the mean productivity
may be a bit less than the productivity of the median hectare in Pimm's 12.2 billion.
Pimm also shows in detail throughout chs. 1-6 (in rough agreement with Vitousek et. al) that we
are now appropriating (using and preventing/foregoing) about 42% of NPP(net primary product
of photosynthesis) or annual biomass growth on land, and 33% of coastal sea productivity. This
implies an average hectare usage:
10 billion x 0.42 =
4.20 billion hect
(Land)
2.2 billion x 0.33 =
0.73 billion hect
(Seas)
--------------------------------------------------------------------12.2 billion
=
4.93 billion hect
Total
Pimm vs. GFN today?Dividing this 4.93 billion hectares by 5.3 billion people in the year 1990
(the date of most of Pimm's data) implies an average per capita usage or "footprint" of
0.93hectares per person, which is quite a bit better than the 1.33 g-hectares we derived from the
5
Stuart Pimm, The World According to Pimm p.18.
There are 100 hectares in 1 km2
7
Pimm, p.105.
6
Global Footprint Network figures rolled forward to 2012.
-- Part of the reason is that Pimm's figures also do not include nuclear footprint (but that is small).
-- Is the difference is due to Pimm's42% of NPP figure being based largely on 1990 data?We
might think so, because the updated GFN chart shows a total footprint in 1990 of around 1.2 x
biocapacity (11.9 billion) = 14.28 billion g-hectares. And roughly 55% was non-carbon = 7.864
g-hectares. If we divide this by a population of 5.3 billion we get 1.48 g-hectares per person. And
this is still much larger than Pimm's figure.
-- And this agrees with the pp footprint line, which showed a per capita footprint of about 2.65 ghectares pp in 1990 (a peak point), of which about 1.45 g-hectares pp was non-carbon.
-- So the difference seems to be due largely to Pimm's methodology being more conservative. The
GFN is including some other non-carbon factors, perhaps such as increasing exhaustion of some
fishing grounds.
V. Three Ways of Estimating Carbon Footprint
1. Now carbon footprint is sometimes measured just in terms of the amount of carbon dioxide
(and sometimes other greenhouse gases, esp. methane) released per person or their expected
effects via warming, e.g. how much productive land might be lost – net -- from temperatures
rising a degree, some dry areas drying out further, and sea levels rising. Focusing only on sea
level rise, carbon footprint might equal 2-4% of the productive land on earth, depending on how
high sea level goes.
-- But that is in productive coastal areas, so in terms of “global hectares” of average productivity
it would be more like 5-7% of all global hectares = 60 -83 million of the 11.9 billion g-hectares.
2. Global Footprint Network takes a very different approach, looking at how much land for green
growth and unharvested shallow seas are needed to absorb these greenhouse gases – e.g. how
much forest and farmland would be enough to breath in these gases (thus directly paying for our
greenhouse gas emissions in land “sinks”). This is what makes their carbon footprint calculation
so large (we’d have to reforest vast parts of the world to eat so much carbon).
3. An intermediate estimate for assessing human ability to get through the 21st century bottleneck
without disaster would be to include the following actual impacts on land & seas:
 losses of land from sea level rise,
 land drying, becoming less productive, speeding desertification due to changes in rainfall,
 loss of coral reefs due to bleaching, reducing fishery productivity, and
 loss of freshwater for irrigation due to weather shifts as well,
 along with some land set aside for reforestation to the point that (with a shift to green energy)
global greenhouse gases stop increasing. Of course, this is rather optimistic.
Let me guess (rather conservatively) that this method would
generate a figure around 15% of all productive hectares.
-- Obviously that would reduce the figure of 11.9 billion ghectares to 10.12 billion g-hectares.
-- We will add this figure into our projections based on
Pimm's more conservative estimate of per capita footprint.
Now we are ready to do forward projections with these
figures, taking population increase into account.
VI.Attempted Projections for our Future Land & Seas Footprint
Scenario 1a– Pimm's lower pp footprint figures; only non-carbon footprint increases; and a
base UN estimate of 10 billion people by peak population.
1. Based on the UN estimate in 2010, assume 10 billion people as the peak human population
reached by the year 2100. [This tallies well with Walter Dodds' analysis, which takes into
account population momentum driving increases long after flat fertility rate is achieved -- see
Dodds, Humanity's Footprint,13-15].
2. Assume that Pimm's average per capita non-carbon footprint increases by 10% due to
economic development in the Third World, and slowly rising GDP in the developed world as
well (leading to expansion of farmland for crops, more land put into irrigation, more razing
lands for more livestock, meat, suburban sprawl etc).
-- This is the big issue, where most of the difficulties with such a projection lie.
-- Change in per-person non-greenhouse footprint depends very much on how much greater
efficiency from improved technology allows us to increase economic output without more
"throughput" of environmental resources, i.e. with increases in what GFN calls "intensity"
of usage -- getting more out of same inputs.
-- In recent decades, pp non-greenhouse footprint has actually been declining (or so it first
appears). We saw a 19% increase in total non-carbon footprint in the GFN figures from
1961 - 2007, but population also tripled during that period, so pp. non-carbon footprint
actually fell significantly. But as population growth levels off and standards of living rise,
non-carbon impacts on land and seas are likely to rise per capita. More on this below.
3. Pimm figure of 0.93hectares ppnon-carbon footprint x 1.1= 1.023 hectares per person by
2100, with my estimated 10% pp growth.
4. Then implies 10 billion people x 1.023 hectares = 10.23 billion g-hectares used/foregone.
5. Which is 86% of the available 11.9 billion hectares of productive land and shallow seas,
assuming that this all stays intact until 2100.
-- Very little would then left over for wilderness and biodiversity.
-- 10% of actual land is enough to preserve key hotspots, but these are much more productive
than average hectares -- even 8% of land in hotspots could easily be 20% of the g-hectares.
Scenario 2a: Only carbon increases -- assume no increase in per capita non-carbon footprint.
1. Based on the UN estimate in 2010, assume 10 billion people as the peak human population.
2. 2012 adjusted Pimm figure of 0.93hectares pp non-carbon footprint x 10 billion = 9.3 billion
g-hectares used, which is 78% of the available 11.9 billion hectares of productive land + seas.
3. With a15% reduction in the capital base of the biosphere (the productive principal) due to
global warming we have 10.12 billion g-hectares. 9.3 billion then = 91.2% of this remaining
available productive land and seas.That is very close to the limit.
4. This leaves less than 8.8% for all other species on earth, and some of this will be in shallow
seas. If only 6.5% of land is left as wilderness, far too little for biodiversity will remain.
Scenario 3a: Both warming effects and per person consumption increases.
-- take the 10.23 billion g-hectares we use in scenario 1 with the 10% pp footprint increase.
-- take the 10.12 billion g-hectares available after a 15% reduction in biocapacity due to warming.
-- this implies human use of 101.5%of remaining productive g-hectares of land and seas.
That is a verydestructive scenario in which the principal base will erode much further and faster.
Scenario 1b: re-run the figures with higher GFN figures for pp non-carbon footprint
We already saw that in 2012, GFN estimates that non-carbon footprint is about 78% of what the
Earth can sustain. So we know that increasing population on this figure will take us well beyond
the sustainable limits.
-- take the GFN figure was 1.33 g-hectares pp of non-carbon footprintx 10% increase = 1.46 pp
-- multiply this by 10 billion = 14.6 billion g-hectares (out of an available 11.9 billion g-hectares).
That is a 26% overshoot that would lead to massive harm to the productive base of the biosphere
and all associated ecosystem services, and huge dieoffs in the human population.
Scenario 2b: GFN pp non-carbon footprint stable, with warming loss = to 15% ave. land
-- 1.33 g-hectares pp (not increasing by 2100) x 10 billion people = 13.3 billion g-hectares, which
is already well more than the available 11.9 billion.
-- compared to 10.12 billion g-hectares remaining after warming on moderate warming estimate.
-- that is a 31% overshoot with enormous destructive results.
Scenario 3b: combine moderate warming loss with 10% increase in GFN pp non-carbon fp
The results of combining the changes in scenario 1b and 2b are unimaginable.
-- 1.46 g-hectares pp. x 10 billion people = 14.6 billion g-hectares
-- and 10.12 billion g-hectares remaining after warming.
-- a 44% overshoot, developing over decades towards 2100, would surely mean the end of most
wild species on Earth, the death of perhaps a quarter of humanity, and an economic crash that
could put most of the surviving people back to early 20th century standards of living at best.
Scenario 4: Balance
Another way to look at these figures is to ask how much ave. per person non-carbon footprint
would have to come down (due to technological improvements and conservation) to keep the
human race within sustainable limits through peak population.
-- We saw that it can be done on Pimm's figures as long as we keep pp non-carbon footprint flat.
-- With GFN figures, assuming a 15% loss of land and productive shallow seas due to warming,
we need to bring non-carbon footprint down to less than 1 g-hectare per capitaso that with 10
billion people, we are using only 10 billion g-hectares.
-- That is a 33% reduction in pp non-carbon footprint. And it still leaves almost nothing left for
wilderness or biodiversity.
Scenario 5: Utopia: Biodiversity Hotspots Saved
Suppose we succeed in setting aside 8% of the world’s land for wilderness and biodiversity,
mostly in tropical rainforests. Assume these on average have more than twice the productivity of
an average hectare of land and shallow seas = 20% of bioproductivity, or 20% of the g-hectares.
-- This reduces the hectares available for human use from 11.9 to 9.5 billion g-hectares.
-- Even with a loss of only 10% more due to warming, we are then down to 8.6 billion g-hectares
for human use, not counting the biodiversity hotspots.
-- With 10 billion people, that is a maximum of 0.86 g-hectares per person non-carbon footprint.
-- 5(a): that is about a 7.5% reduction in ave. per capita usage on Pimm's figures.
-- 5(b) and about a 35.5% reduction in ave. per capita footprint from the GFN figure.
-- These reductions would have to be achieved despite rising meat/dairy consumption
-- That puts a lot of pressure on technological improvements to cut pp non-greenhouse footprint.
This might be about the very best scenario we could reasonable hope for by 2100.
VII. Drivers of per-person Land and Seas footprint increases (Speth, Dodds, Brown, Rosa):
These scenarios show how crucial it is to develop accurate projections of per capita non-carbon
footprint changes for the coming decades; right now, these projections do not appear to exist.
 We can estimate likely increases in energy use and world GDP, but much of these pp changes
are growth in fossil fuels usage. But it also includes
-- land stripped for coal, or used for natural gas extraction, and seas used for oil well drilling ;
-- we can count this as an indirect use of land bioproductivity, or reduction in principal base.
 Long-term projections for global GDP increases that still rely on more resource throughput:
-- Dodds says world GDP doubled in last 25 years (p.17). Suppose (conservatively) that it
only doubles again by 2050 with a population of 9 billion [many scenarios show it more
than quadrupling by 2050 -- as shown here]. That is 55.5% more GDP per capita than now.
-- A lot then depends on how much technological improvements in efficiency can hold down
increases in land and seas resource usage to feed GDP growth (or even perhaps get more out
of less land usage in some sectors). Consider all the following:
-- land mined for other minerals used in productive processes (e.g. metals);
-- land used for new buildings and roads (human built-up areas);
-- land used for wood for paper and construction, for cotton, other consumables (e.g. palm oil)
-- If GDP pp increases 55.5% and only 1/4 of this is from increases in these kinds of
throughput, with 3/4 coming from better technology, that is still a pp. non-carbon footprint
increase of 13.87%, which is more than the 10% that I plugged into Scenario 1 for year 2100
(50 years later). So by this measure, my 10% estimate looks very optimistic indeed.
 But we saw that pp non-carbon footprint had fallen from 1961 to 2012, and that is largely due
to the amazing increases in efficiency of farming and food production in general (including
fishing) due to new technology and more intensive extraction from lands and seas.
-- The "green revolution" tripled grain yields to 3.3 tons per hectare, largely as a result of
* new strains of crops that use less water, such as "dwarf" wheats from Japan;8
* vast increases in irrigation, which produces about 40% of global grain harvests, and uses
70% of world freshwater usage annually, resulting in almost a 280% increase in irrigated
areas since 1950.
8
See Lester Brown, Full Planet, Empty Plates: The New Geopolitics of Food Scarcity (W. W. Norton Co, 2012 -Earth Policy Institute), pp.73-75.
* huge increases in use of fertilizers (from 14 million tons in 1950 to 177 million tons in
2010 !), pesticides, herbicides, and other industrial chemicals;
* more high-tech farm machinery in use across more of the world.
These are huge increases in efficiency, but it is not
evident that they can continue to keep pace with a
43% increase in people by 2100:
 The amount of arable land has only risen about
10% since 1961 to about 1.4 billion g-hectares.
So most of the gains in food production were
from technology. It is unclear that this can continue for much longer.
-- in many places, yields on the same land are no longer rising; all the methods to increase
them further have been used. Japan has seen no increase in rice yields in 17 years.
-- rice yields in China are very close to those in Japan, i.e. near the apparent limits;9
-- and wheat yields have hit their limit in Western Europe.
-- still, much of the best arable land
in Africa, e.g. in Rwanda and
Tanzania, can be farmed more
intensively if the people are
willing to accept the other
ecological costs of more
industrial chemical in farming.
-- against this hope is set the fear of
further soil erosion in the Sahel
regions in northern Africa.
9
Brown, Full Planet, Empty Plates, pp.79-81.
 Water used for irrigation is also running into limits in many parts of the world, and irrigated
areas are falling in the US, the Middle East, and soon in India, Pakistan, China, and Mexico.10
-- it is possible that this could be partly offset by new dams, but these have other impacts on
river ecosystems and watersheds, and there are fewer candidate places left with most rivers
in populated areas already heavily dammed and channeled.
-- the other hope lies in new technologies like drip irrigation, but even if it doubled the amount
of crops from irrigation, that is not be enough to keep pace with a rise to 10 billion people.
-- or massive hydroengineering projects to move flood waters to drier areas where they are
needed (e.g. from Mississippi to aquifer under Oklahoma) or to capture monsoon rains in
massive reservoirs and pump them north (e.g. from SE Asia) -- very energy-intensive.
 As more of the world's population emerges from poverty, there is an increasing consumption
of meat (and milk and eggs), resulting in need for more grains and grazing lands.
-- but if grain yields per hectare start to peak in many places, larger animal herds will be
competing with growing human populations for grain-based foods, esp. soybeans.
-- population of livestock increases in proportion with human population, e.g. in Africa:11
people
livestock
1950
227 million
300 million
2009
1 billion
862 million
-- nearly 400% increase
-- nearly 300 % increase
-- but range animals in particular have a nearly fixed footprint per head; they use more land as
their numbers rise, until the exceed the carrying capacity of the available foliage.
In short, then, unless new technologies can extract at least 43% more from the same land and
seas, driving per capita usage down that much by 2100, then total extraction or throughput will
have to increase -- more of the total available bioproductivity of land and seas (annual 'interest')
will have to be used each year, thus expanding total human non-carbon footprint. How?:
 More arable land can be gained by cutting forests, but much of this yields land that is too poor
to be harvested at high yields for long, and reverts to grazing land in a few years. And the
losses to biodiversity and ecosystem services are huge when tropical forests are cut.
 Increasing fish harvests relative to population despite looming exhaustion of some fisheries;
 Freshwater usage is projected to double by 2050 (beyond which we guess): while population
climbs perhaps 30%, per capita usage will increase by about 60% (partly due to more meat).
-- that is a large jump in pp water footprint, which we left out of our earlier projections.
-- and the human race is already using 50% of the currently accessible runoff. Doubling takes
us to 100%, which is impossible. We will have to capture more runoff in ways noted above.
In sum: "Tremendous increases in productivity of cropland made possible by technology in the
past 50 years may not be duplicated. Most high-quality areas for growing food are already under
cultivation. Increasing food production will take a large environmental toll ... Converting natural
lands to croplands endangers species, water supply, and water quality [given chemical runoffs].
As we demand more from marginal lands, wind erosion increases.... (Dodds, p.29).
10
See Lester Brown, World on the Edge: How to Prevent Environmental and Economic Collapse (W. W. Norton Co,
2011 -- Earth Policy Institute), pp.21-30
11
See Lester Brown, World on the Edge, p.40.
VIII. Likely Losses in the Principal Base of the Biosphere (reducing total biocapacity)
As this passage from Dodds suggests, a lot of the factors that we have been considering as driving
pp non-carbon footprint up (as technological improvements in efficiency try to bring it down)
might be more easily modeled in our projections as reductions in the bio-endowments that
produce the annual 'interest' we consume off of 11.9 billion productive g-hectares.
Warming. So far, I only modeled losses due to warming from greenhouse gases as reductions in
the principal base of the world's ecosystems that produce the green growth we use or displace.
-- A lot of the loss in productivity from sea level rise would come from loss of coastal wetlands
that are highly fertile, and rice fields near coastal estuaries in Asia: “Even a 3-foot rise in sea
level would sharply reduce the rice harvest in Asia…It would inundate half the Riceland in
Bangladesh and would submerge part of the Mekong Delta [in Viet Nam].12
-- To these effects should be added the loss of river flows from declining glaciers and winter
snows in central Asia. Four rivers sustaining the most populated areas on Earth – the Indus,
Ganges, Yellow, and Yangtze rivers – all depend on ice melting each summer from Himalayan
glaciers. Flow in these rivers could drop by 50%; even a 20% drop would be disastrous to their
use for irrigation in the dry seasons.
Overuse Factors: Topsoil Loss, water, and others. But there are many other serious causes of
declines in theproductive bases of various ecosystems around the world. As we saw, some of the
biomass used or forgone in Pimm's calculation is really due to loss of 'principal' in the world's
biological 'fund,' since it is the biomass not grown because of the degrading of the land’s
productive capacity:
 paving over land for roads, parking lots, buildings -- suburban sprawl. The US has paved an
area equal in size to the state of Georgia.
 increasing amount of land near cities and mines taken up for landfills, wastes, which continue
to increase despite recycling (which only lowers their rate of increase).
 drylands lose productivity through overgrazing, and may regain this capacity only very slowly
if left fallow. Instead, soils may blow away, or be lost through water erosions in heavy rains;
invasion by woody shrubs may also make the land useless for grazing when grass is gone.
-- Brown describes two giant dust bowls forming in northwest China into western Mongolia,
and in the Sahel regions around the Sahara desert. According to Wang Tao, a global expert,
the following amount of dry lands (mostly grazing lands) turned into desert each year:13
1950 - 1975
1975 - 1987
1987 - 2010
Ave of 600 square miles / year
Ave of 810 square miles / year
Ave of 1390 square miles / year
Total: 15,000
Total: 9,720
Total: 31,970
That is 56,690 square miles (x 259 hectares per square mile) = 14,682,710 hectares
= about the area of the state of Georgia again. If this rate of soil loss increases, it will
eventually outstrip our capacity to irrigate more land to compensate.
 in rain-fed croplands also, topsoil is lost through over-farming and loss of trees that serve as
windbreaks, resulting in these lands changing to less productive grazing land;
12
13
See Lester Brown, World on the Edge, p.49.
See Lester Brown, World on the Edge, pp.38-39.
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-- Brown: “Today, a third of the world’s cropland is losing topsoil at an excessive rate.”14
conversion of more productive tropical forest to less productive farmlands andgrazing lands;
invasive species reducing productivity of rivers and arable land;
irrigated croplands are degraded through salination and lose productive capacity they had as
drylands before irrigation;
loss of irrigated land due to drying up of overused aquifers, as per Brown’s predictions;
destruction of rivers, coral reefs, estuaries, and shallow coastal seas by agricultural runoff (due
to increasing farming chemicals), toxins, dynamiting for fish, and more dams;
decline in productivity of fisheries, half of which are now overfished or fished to capacity.
It is very hard to estimate the likely total loss to productivity of the "capital base" of the biosphere
due to such factors by peak population around 2100. The following is a conservative estimate of
those reductions:
Scenario 6: Loss of 9% more of capital base of biosphere due to overuse factors.
-- 15% drop in average productivity in rivers and shallow seas (= reduced fish stocks).
-- 8% drop in average productivity of lands
This would leave us with 10.79 g-hectares, which is more than a 9% cut in the total available.
This can then be added to any of the earlier scenarios.
-- For example, we deduct another 10% of the original 11.9 billion for warming, which leaves
9.6 billion g-hectares after degradation and greenhouse effects.
-- So even to achieve balance, without anything left for biodiversity, we need to bring the average
non-carbon footprint down to 0.96 g-hectares pp before peak population. That is about a 38%
reduction in average per capita non-carbon footprint.
Can we add to the biosphere's productivity?
I have assumed in this analysis that we cannot add significantly to the biomass produced on land
and in shallow seas. Rainfed cropland itself is not increasing much: Pimm says roughly 15 million
km2 (or 1.5 billion hectares) since the 1960s, with only about a 1% net increase since then. This
stability masks opposing forces:
+ conversion of forest land into rain-fed cropland
+ expanding farming on to uncultivated non-forest lands: 445,000 million hectares =
= a 20% increase possible, largely through land in Africa.
+ increasing productivity on arable land already farmed -- Foley
- loss of rain-fed cropland taken from tropical forests as it reverts to dry grasslands
- loss of rain-fed cropland due to soil erosion (affects grazing lands more).
These factors have been competing; thus cropland has had net slow growth in recent decades.
The same is true for the net 1% average increase in irrigated cropland each year, which includes;
+ irrigation of more dry lands for cropland
- loss due to salination from irrigation and loss of water sources (which will speed up).
There are only four ways I can see of massively increasing biomass productivity on land:
 enormous increase in irrigation using expensive water from desalination plants, powered by
14
See Lester Brown, World on the Edge, p.38. I assume it desertification continued at same rate since 2000.
sustainable energy that does not add to our carbon footprint (how? $6 a gallon water?);
 figuring out how to control weather and causing more rain to fall on currently dry areas (a
science-fiction, but it would help a lot of we could redirect rain!);
 massive reforestation projects in grasslands that were previously forest or that can sustain
forests (would require enormous areas and massive investment, and would eat into arable land
and grazing land);
 and bringing intensive factory farming to areas of Africa that do not presently have it, so as to
increase greatly the productivity of these lands (as is already happening with foreign nations
buying and leasing African lands for farming).
The first of these seems barely imaginable (probably we’ll only manage a small increase via
desalination), and the second is technologically unimaginable now. The third is economically
unimaginable too, though it would help a lot with carbon reduction to reforest. The fourth is
feasible and will probably account for the 50-60% increase in grain we need by 2050. The
question is how much it can increase the productivity of an average hectare worldwide.
Conclusion: our present rates of land and seas usage, coupled with increases in the average usage
rates and increases in population, is clearly unsustainable for human beings and other species.
-- we have to control population growth by a global Marshall Plan to end the worst poverty in the
developing world, via local development and political reforms that get rid of tyrannies and
kleptocratic warlords;
-- we have to keep average pp non-carbon footprint from rising much by increasing productivity
further on the arable land we have, by preventing large increases in meat consumption
worldwide, and by technofixes and efficiency controls for sufficient freshwater;
-- we have to adopt a tough global greenhouse gas treaty with carbon cap & trade regime
-- we have to set aside at least 8% of hotspot lands and seas for wilderness and biodiversity.
Per capita footprint now in different parts of the world.