Population Dynamics After Caughley: The Grand Vision

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Is Modern Agriculture Sustainable?
An Ecologist’s View of Agricultural
Science
Charles J. Krebs
Department of Zoology
University of British Columbia
Outline of Talk
Ecology to what purpose?
 A triumvirate of problems:
Agriculture – Biodiversity - Population
 Ecological principles for guidance in
helping to solve the agricultural crisis
 Summary

Ecological
understanding
Management
recommendations
Policy
implementation
The
Politics
of
Ignorance
Basic Principle # 1
 The earth has physical, chemical,
and biological limitations
- it is the only planet we have
Are Current World Practices
Sustainable ?
Three key areas
- Agriculture
- Biodiversity
- Population
 Two steps for ecologists:
- evaluate the current situation
- suggest solutions to current problems

Global Distribution of Hunger: Quantified
by the 2012 Global Hunger Index
Wheeler, T. and J. von Braun. 2013. Climate change impacts on global food security.
Science 341:508-513.
Global Yield Trends in Rice and Wheat
10
target
Yield (tons per ha)
8
%
2.4
6
er y
p
%
1.0
4
pe
e
ry
ar
target
ear
Rice
er ye
0.9% p
2
ar
Wheat
0
1960 1970 1980 1990 2000 2010 2020 2030 2040 2050
Ray, D. K. et al. 2013. Yield trends are insufficient to double global crop production
by 2050. PLoS ONE 8:e66428.
Global Agricultural Land Area
Land area (km2 x 106) ha
6
Total Agricultural Area
5
4
Meadows and Pastures
3
Since 1991 no change in land area used
2
Arable Land and Crops
1
0
1970
Source: FAOSTAT, 2013.
1980
1990
2000
2010
Five Solutions

Stop expanding agriculture’s footprint

Close the world’s yield gaps

Use resources more efficiently

Shift diets away from meat

Reduce food waste
Foley, J. A. 2011. Can we feed the world and sustain the planet?
Scientific American 305 (5): 60-65.
Maize Yield in Africa Cropland
Currently operating at 10-30% of potential
tonnes per ha
Yield in 2000
Potential Yields
Under optimum use of
rainwater, nutrient, weed,
and disease management
Bindraban, P. S. et al. (2012). Assessing the impact of soil degradation on food
production. Current Opinion in Environmental Sustainability 4:478-488.
Agriculture

Premise: Agriculture is applied ecology
- if this is correct, agriculture must
operate under the principles of
applied ecology

What principles of applied ecology are
applicable?
Agriculture – Fundamental Issues

Agriculture reduces biodiversity
- is this reversible?

Agriculture exacerbates climate change
- can we neutralize this?
Agricultural Sustainability - # 1

Ecological Generalisation # 1:
ecosystems must run on solar energy
- current agriculture runs on nonrenewable resources (oil, natural
gas, coal)

Agriculture must transition to
renewable energy
- whither industrial agriculture?
Agricultural Sustainability - # 1

Agriculture can continue to use nonrenewable resources only if it can
remove their harmful effects on the
air, water, and land

This is a very important technical
problem in energy engineering that
is beyond my expertise to discuss
Agricultural Sustainability - # 2

Ecological Generalization # 2:
nutrient input = nutrient output
- crop production depends on
fertilizer inputs

Nitrogen limits productivity in many
soils

Phosphate is also required in fertilizer
Fertilizer Problems - # 1

Nitrogen is both a positive and a
negative factor
- crop production depends on
fertilizer inputs
- biodiversity declines with
nitrogen inputs
- water pollution results from
excessive nitrogen runoff
Global nitrogen fixation, natural and
anthropogenic, for 2010
Biological
Nitrogen
Fixation
Fowler, D., et al. 2013. The global nitrogen cycle in the twenty-first century. Philosophical
Transactions of the Royal Society of London B: 368: doi 10.1098/rstb.2013.0164.
Effects of Nitrogen Fertilizer Input on Plant
Biodiversity in Europe
No. of plant species per 100 m2
80
70
60
50
more nitrogen fertiliser = fewer plant species
40
30
20
10
0
0
50
100
150
200
250
300
350
400
450
Annual Nitrogen input (kg/ha/year)
Kleijn, D. et al. (2009). On the relationship between farmland biodiversity and land-use intensity in
Europe. Proceedings of the Royal Society of London B 276:903-909.
Corn Yield - Iowa
Corn grain (tonnes per ha)
12
10
8
6
4
0
50
100
150
200
250
300
Nitrogen fertilizer - kg/ha
Cerrato, M.E., and Blackmer, A.M. 1990. Comparison of models for describing corn yield
response to nitrogen fertilizer. Agronomy Journal 82: 138-143.
350
Agricultural Sustainability - # 3

Fertilizer
- nitrogen is produced from natural gas
- phosphate comes from rocks

Nitrogen production is tied to oil in
availability and price

Phosphate is limited to rock formations
World Rock Phosphate Production
Production (Mg/year)
Peak phosphorus ≈ Peak oil
Year
Dery, P. and Anderson, B. 2007. Peak phosphorus. Energy Bulletin 13 August 2007.
World Phosphorus Fertilizer Use
50
Million tons P2O5
40
1.8% growth
30
4.6% growth
20
10
0
1960
1970
1980
1990
2000
2010
Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a vigorous
debate about long-term phosphorus security. Sustainability 3:2027-2049.
Phosphorus - # 1

An essential element for all living organisms

Renewable P from bird guano
- Nauru, Christmas Island, now gone

Non-renewable P from igneous and
sedimentary rocks
- Morocco, China, USA mainly
- a finite resource
Scholz, R. W., and F.-W. Wellmer. 2013. Approaching a dynamic view on the availability of
mineral resources: What we may learn from the case of phosphorus? Global
Environmental Change 23:11-27.
Phosphorus - # 2

Will we run out of phosphorus?

Quality and accessibility of remaining
reserves are decreasing
- costs will thus increase

Extremely variable estimates of how much
phosphorous is left in rocks
Neset, T.-S. and D. Cordell. 2012. Global phosphorus scarcity: identifying synergies for
a sustainable future. Journal of the Science of Food and Agriculture 92: 2-6.
Lifetime of World Phosphate Rock Reserves
Author
Estimated
Estimated year
lifetime of
of depletion
Assumptions
reserves
Tweeten (1989)
61 years
2050
3.6% increase in demand
Runge-Metzger (1995)
88 years
2083
2.1% increase in demand
60-130 years
2058-2128
2-3% increase in demand
Smil (2009)
80 years
2080
At current rate of extraction
Fixen (2009)
93 years
2102
At 2007 production rate
69-100 years
2078-2109
90 years
2099
At current rates
300-400 years
2310-2410
At current rates
Steen (1998)
Smit et al. (2009)
Vaccari (2010)
Van Kauwenbergh (2010)
0.7% to 2% increase to 2050
Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a
vigorous debate about long-term phosphorus security. Sustainability 3:2027-2049.
“If ‘Plateau Phosphorus’ does describe future production, the new
reserve figures could add 168 years to production availability.”
Mew M. Future phosphate rock production – peak or plateau? Retrieved June 12, 2012,
from http://www.fertecon-frc.info/page15.htm
Phosphorus - # 3

Does the “Peak Phosphorus” curve apply to
future supplies?

The analogy with oil production is not valid
because oil can be substituted by other
energy sources

There is nothing known that can substitute for
phosphorus
Scholz, R. W. and F.-W. Wellmer. (2013). Approaching a dynamic view on the availability of
mineral resources: What we may learn from the case of phosphorus?
Global Environmental Change 23:11-27.
Phosphorus - # 4

There is a limited amount of phosphorus
available on the Earth
- everyone seems to agree on this

Recycling and recovery must be part of the
phosphorus management strategy

There are now movements in this direction
Rhodes, C. J. 2013. Peak phosphorus - peak food? The need to close the phosphorus cycle.
Science Progress 96: 109-152.
Agricultural Sustainability - # 4
Soil erosion is a critical problem that is a
central issue in nutrient losses
 What is the state of soil erosion in
agricultural areas?

Soil Degradation Penalty for Food Crops in China
Business
as usual
2030
Double soil
Degradation
2030
Food production decline of 14% to 30%
Business
as usual
2050
Double soil
Degradation
2050
Ye, L. and E.Van Ranst. (2009). Production scenarios and the effect of soil degradation on longterm food security in China. Global Environmental Change 19:464-481.
Agricultural Sustainability - # 5
Climate change is happening
 Four broad impacts on agriculture:
- changes in the distribution of rainfall
and temperature
- increased variability of weather
- changing crop productivity (C3, C4)
- coastal crops and sea level rise
 Soils do not move….

Rising CO2 Levels

Increasing CO2 increases the yield of
C3 crop plants

Increasing CO2 does not increase the
yield of C4 crop plants

Drought stress can be reduced in C4
plants because of lower stomatal
conductance
Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the
future of C4 crops for food and fuel. Proceedings of the Royal Society B:
276:2333-2343.
Percentage of agricultural land used for the
production of C4 crops in 2006
Main C4 crops are maize, sugar cane, millet and sorghum
Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the
future of C4 crops for food and fuel. Proceedings of the Royal Society B:
276:2333-2343.
Change in Cereal Production and
Population Growth, 1970-2010
cereals
End of the Green Revolution
people
Source: FAO
Agricultural Sustainability - # 6

Solutions
- recycle nutrients
- reduce fossil fuel use
- low tillage, organic agriculture?
- develop better crops, diversify
- improve grazing management
- integrate crops and livestock
- stop using food for biofuels
- invest in agriculture
Agricultural Sustainability - # 7
What should you eat?
 Ray Hilborn and his research group
have computed the environmental
impact of animal foods
 213 studies, 16 production technologies,
9 measures of impact
 Life Cycle Assessments

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods.
Proceedings of the National Academy of Sciences USA (in review).
Energy Used
In Production
Energy (MJ per 40 g protein
better
worse
Aquaculture
Capture
fisheries
Livestock
Hilborn et al. (2014) PNAS
best for milk, worst
for catfish aquaculture
Greenhouse
Gases
outputs
Greenhouse Gas output (Kg CO2 per 40 g protein
better
worse
Aquaculture
Capture
fisheries
Livestock
Hilborn et al. (2014) PNAS
best for molluscs, worst
for beef production
Agricultural Sustainability - # 8
What should you eat?
 Rank all food groups by 9 measures:
- energy
- greenhouse gases
- acidfication - eutrophication
- land used
- water used
- pesticides
- antibiotics
- soil loss

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods.
Proceedings of the National Academy of Sciences USA (in review).
Agricultural Sustainability - # 8
What should you eat?
 Rank all food groups by 9 measures:
- energy
- greenhouse gases
- acidfication - eutrophication
- land used
- water used
- pesticides
- antibiotics
- soil loss

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods.
Proceedings of the National Academy of Sciences USA (in review).
Environmental Impacts of Food Groups
Beef
Chicken
Catfish
Pork
Eggs
Shrimp
Tilapia
Carp
Milk
Finfish
Invertebrates
Salmonids
Whitefish
Large pelagics
Snall pelagics
Shellfish
worse
better
0
2
4
6
8
10
12
14
16
Average Rank
Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods.
Proceedings of the National Academy of Sciences USA (in review).
Agricultural Sustainability - # 9
The Bottom Line: What should you eat?
 Food security for the Earth would be
improved if we ate more vegetables
 Even with this change, there are many
problems that need addressing
 For any meat consumption, the devil is in
the details, e.g. milk (good for energy,
poor for water use, antibiotics, soil)

Biodiversity

Premise: biodiversity provides a planet
that is inhabitable by humans
- if this is correct, protecting
biodiversity must become a
major societal goal
Biodiversity – Constraints
We do not have a description of the
existing life on earth
 We have a rudimentary understanding
of how ecological communities
operate
 Land clearing for agriculture has been a
major cause of biodiversity loss
- yet we need more food

Ecosystem Services

Coda:
- there is an ever growing literature about
the value of biodiversity and ecosystem
services
- much of this discussion is good political
ecology but hopeless scientific ecology
- we should protect biodiversity because we
cannot eat iron ore or coal or phosphate
rock or paper money…..
Power, A.G. (2010). Ecosystem services and agriculture: tradeoffs and synergies.
Philosophical Transactions of the Royal Society B 365: 2959-2971.
45
The Population Problem
o Ecological Generalization # 3:
- no population increases indefinitely
o The human population of the Earth now
exceeds the carrying capacity of the planet
o Bringing the human population back to some
sustainable level is a critical social issue
Global Ecological Footprint
1.8
Fraction of the planet
being utilised
1.6
1.4
1976
1.2
1.0
Carrying capacity of the Earth
0.8
0.6
0.4
0.2
0.0
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
Source: Living Planet Report 2010
Year
The Politics of Ignorance
 Operational Principle: what you do not
know cannot hurt you
- you can operate in this state by ignoring
evidence-based science, or
- you can fail to fund the scientific research
that will shed light on specific problems
The Politics of Ignorance # 2
 Major current example: climate change
- “there is no need to do anything until we
have scientific certainty”
- how should we respond to scientific
uncertainty ?
- technological optimists vs. technological
pessimists
The Bottom Line




Scientists do not make policy
But we know a great deal about the natural
world that should inform policy but is not
used
We must continue to do good science and ask
our governments to use evidence-based
policies
There is some hopeful evidence that the
ecological world view is slowly replacing the
economic world view
Summary - # 1


Three critical world problems have their
roots in ecology:
- agricultural production
- biodiversity conservation
- human population growth
Our job as scientists is to recognize the
connections between these three
problems and to work toward ethical
solutions
Summary - # 2


There is encouraging signs that we are
moving in the direction of sustainability but
perhaps more slowly than scientists would
like
Agricultural scientists are the heros of our
day and should continue to lead the way to
sustainable agriculture and human
betterment
- (I will not list who the bad guys are…)
Thanks for listening !

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