Ecological Theory, Pest Management, and Conservation Biology: Lessons for Rice Ecosystems

1
Ecological Theory, Pest Management, and
Conservation Biology Lessons for Rice Ecosystems

• Dr. Charles J. Krebs
• University of Canberra
• and
• University of British Columbia

2
Starting Assumptions

• Ecology has sprung from a basis in practical
  agriculture
• During the last 60 years the two fields have gone
  their separate ways
• Have ecologists learned anything during that time
  that might aid agricultural science?

3
Historical Development of Ecology
4
Dilemma 1

• Pest management has been largely an empirical
  science
• Conservation biology is also largely empirical
  but with a bit of theory
• Ecological theory moves along almost divorced
  from empirical reality

5
The Challenge

• Can we bring these disciplines together in such a
  way that they can assist one another?

6
Outline

• Ecological Theory
• Pest Management
• Conservation
• Six Practical Principles for Agriculture

7
A Caveat

• All these disciplines profit from better
  statistical methods and better sampling devices
• I will not discuss this sharing of methodology,
  which is very important for progress

8
Ecological Theory Population Dynamics - 1

• Models of population growth
• Age-based and stage-based population projection
  models
• Elasticity and sensitivity analysis of matrix
  models

Caswell, H. 2001. Matrix population models
construction, analysis, and interpretation. 2nd
ed. Sinauer Associates, Sunderland, Massachusetts.
9
Ecological Theory Population Dynamics - 2

• Models of competition and predation
• Tilmans models of competition
• Functional and numerical response models for
  predators

Hastings, A. 1997. Population Biology Concepts
and Models. Springer, New York.
10
Ecological Theory Population Dynamics - 3

• Models of herbivory
• Caughleys interactive and non-interactive
  models of plant-herbivore
• Few theoretical models

Olff, H., V. K. Brown, and R. Drent, editors.
1999. Herbivores Between Plants and Predators.
Blackwell Publishers, Oxford.
11
Ecological Theory Population Dynamics - 4

• Models of disease and parasitism
• Susceptible-Infectious-Resistant models from
  medical epidemiology
• Strong interaction with medical sciences

Anderson, R. M. 1991. Populations and infectious
diseases ecology or epidemiology? Journal of
Animal Ecology 601-50.
12
Ecological Theory Community Dynamics - 1

• Models of equilibrium and non- equilibrium
  community organization
• Disturbance and patch dynamics
• Highly relevant to agricultural systems

DeAngelis, D. L., and J. C. Waterhouse. 1987.
Equilibrium and nonequilibrium concepts in
ecological models. Ecological Monographs
571-21. .
13
Ecological Theory Community Dynamics - 2

• Models of nutrient cycles
• Input-output models of soil nutrients
• Sustainability of nutrient budgets
• A central issue for agriculture

Newman, E. I. 1997. Phosphorus balance of
contrasting farming systems, past and present.
Can food production be sustainable? Journal of
Applied Ecology 341334-1347.
14
Ecological Theory Community Dynamics - 3

• Models of food webs
• Complex food webs show surprises
• Indirect effects
• Law of Unintended Consequences

Williams, R. J., and N. D. Martinez. 2000. Simple
rules yield complex food webs. Nature
404180-183. Paine, R. T. et al. 1998. Compounded
perturbations yield ecological surprises.
Ecosystems 1535-545.
15
Ecological Theory Community Dynamics - 4

• Diversity and Stability Hypothesis
• High biodiversity high stability
• Monocultures lead to pest and disease outbreaks
• A central issue for the agriculture of
  monocultures

McCann, K. S. 2000. The diversity-stability
debate. Nature 405 228-233. Worm, B., and J. E.
Duffy. 2003. Biodiversity, productivity and
stability in real food webs. Trends in Ecology
Evolution 18 628-632..
16
Ecological Theory Landscape Dynamics - 1

• Central Idea
• Landscape ecology argues that what happens at
  one spatial scale may depend on the character
  of the broader landscape.
• A central issue for the geometry of cropping
  systems

Büchs, W. 2003. Biotic indicators for
biodiversity and sustainable agriculture-introduct
ion and background. Agriculture, Ecosystems
Environment 981-16.
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Ecological Theory Landscape Dynamics - 2

• Relevance to Agriculture
• Landscape ecology is possibly the most relevant
  ecological discipline for sustainable
  agriculture
• It is also the least well developed of the
  ecological disciplines

Turner, M. G. et al. 2001. Landscape Ecology in
Theory and Practice Pattern and Process.
Springer, New York. 401 pp.
18
Ecological Theory Complex Systems

• Much interest in complex systems
• Unclear to me how this will help achieve
  agricultural sustainability
• It has been applied to the Western Australia
  wheat belt in the book by Allison and Hobbs
  (2006)

Gunderson, L.H. Holling, C.S. 2002. Panarchy
Understanding Transformations in Human and
Natural Systems. Island Press, Washington, D.C.
507 pp.
19
Applied Ecology Conservation Biology - 1

• Principles relevant to agriculture
• Protect biodiversity
• Protect genetic diversity
• Protect natural habitat
• Provide dispersal corridors

Caughley, G., and A. Gunn. 1996. Conservation
Biology in Theory and Practice. Blackwell
Science, Oxford. 459 pp.
20
Applied Ecology Conservation Biology - 2

• Why protect biodiversity?
• Save the pieces argument
• Products for human health
• Diversity promotes stability
• Unknown amount of redundancy

Edwards-Jones, G. 2007. Is paradigm shifting
worth the effort? Trends in Ecology Evolution
22 116-117.
21
An Immediate Problem

• How much biodiversity is enough?
• Do we have the right biodiversity for
  agriculture?
• We have not even cataloged much of natural
  biodiversity, particularly in insects

Büchs, W. et al. 2003. Biodiversity, the ultimate
agri-environmental indicator? Potential and
limits for the application of faunistic elements
as gradual indicators in agroecosystems.
Agriculture, Ecosystems Environment 98 99-123.
22
Ecosystem Function in relation to Biodiversity
McCann, K.S. 2000. The diversity-stability
debate. Nature 405 228-233.
23
A Potential Conflict

• Conservation biologists typically worry about
  the rare species
• Agricultural scientists may be more concerned
  with the common species - we must consider
  individual species with regard to system
  function

Balvanera, P. et al. 2005. Applying community
structure analysis to ecosystem function
examples from pollination and carbon storage.
Ecological Applications 15 360-375.
24
Applied Ecology Conservation Biology - 3

• Why protect genetic diversity?
• Future evolution potential
• Protect local ecotypes
• Ignorance is not bliss
• Unknown amount of climate change

Joshi, J. et al. 2001. Local adaptation enhances
performance of common plant species. Ecology
Letters 4 536-544.
25
Local Adaptation in Trifolium pratense
By and large the species do best on their home
ground
Joshi, J. et al. 2001. Ecology Letters 4 536-544.
26
Applied Ecology Conservation Biology - 4

• Why protect natural habitats?
• Future restoration is very expensive
• Niche diversification for desirable species
• Diversity promotes stability
• Unknown amount of redundancy

Brooks, T. M. et al. 2002. Habitat loss and
extinction in the hotspots of biodiversity.
Conservation Biology 16 909-923.
27
Arable Weeds in Netherlands
Landscape complexity can compensate for
intensive farming
Tscharntke, T. et al. 2005. Landscape
perspectives on agricultural intensification and
biodiversity-ecosystem service management.
Ecology Letters, 8, 857-874.
28
Applied Ecology Pest Management - 1

• Relevant Principles
• Killing pests does not always reduce their
  abundance
• Understand pest biology
• Avoid poisons if possible
• Use cultural controls

Singleton, G. R. et al. (ed.) 1999.
Ecologically-based Management of Rodent Pests.
Australian Centre for International Agricultural
Research, Canberra, Australia.
29
Applied Ecology Pest Management - 2

• New methods for pest control
• Sterility experiments on insects and
  vertebrates
• Plant biotechnology Bt cotton
• Cultural controls
• Use cultural controls wisely

Bates, S. L. et al. 2005. Insect resistance
management in GM crops past, present and
future. Nature Biotechnology 2357-62.
30
Alternatives to Pesticides

• Bacillus thuringiensis transgenic plants
• High-dose-refuge strategy depends on
  low frequency of resistance genes and high
  fitness cost of these genes
• Chrysomela tremulae in non-Bt areas already had
  1-2 frequency of resistance genes
• Experiments in lab showed high fitness cost of
  these genes in a non-Bt environment

Wenes, A.L. et al. 2006. Frequency and fitness
cost of resistance to Bacillus thuringiensis in
Chrysomela tremulae (Coleoptera Chrysomelidae).
Heredity 97 127-134.
31
European Rabbit in Australia
High sterility yet no drop in rabbit density
Twigg, L.E. Williams, C.K. 1999. Fertility
control of overabundant species can it work for
feral rabbits? Ecology Letters 2 281-285.
32
Six Pragmatic Principles for Agriculture - 1

• Landscape design matters
• Spatial and temporal components what crop to
  grow where?
• Well established in good agricultural systems
• Information is highly site and crop specific

Tscharntke, T. and R. Brandl. 2004. Plant-insect
interactions in fragmented landscapes. Annual
Review of Entomology 49405-430.
33
Cotton Fields in an Agriculture Landscape
Uncultivated land
Sorghum
Cotton
Prasifka, J. R. et al. 2005. Relationships of
landscape, prey and agronomic variables to the
abundance of generalist predators in cotton
(Gossypium hirsutum) fields. Landscape Ecology
19709-717.
34
Six Pragmatic Principles for Agriculture - 2

• Maintain natural habitats interspersed with
  agricultural fields
• Habitat management for pests and for useful
  species like pollinators
• But design the interspersion if possible

35
Pollination by Bees in Coffee
Klein, A.M. et al. 2003. Pollination of Coffea
canephora in relation to local and regional
agroforestry management. Journal of Applied
Ecology 40 837-845.
36
Pollination of Watermelon Crops
Kremen, C. et al. 2004. The area requirements of
an ecosystem service crop pollination by native
bee communities in California. Ecology Letters
7 1109-1119.
37
Six Pragmatic Principles for Agriculture - 3

• Maintain soils by measuring nutrient
  inputs and outputs
• The ecological system in larger than a single
  farm or group of farms
• Critical measurements to demonstrate
  sustainability of farming practices

38
Fertilizer Use in China
Richter, J. Roelcke, M. 2000. The N-cycle as
determined by intensive agriculture examples
from central Europe and China. Nutrient Cycling
in Agroecosystems 57 33-46.
39
Six Pragmatic Principles for Agriculture - 4

• Beware of thresholds
• Ecosystem service relationships may not be
  straight lines
• Typically we cross thresholds and are alerted
  to the problem after the fact
• Very little data are available on thresholds

40
Hypothetical Thresholds
Kremen, C. Cowling, R. 2005. Managing ecosystem
services what do we need to know about their
ecology? Ecology Letters 8 468-479.
41
Pseudoreplication
Pacific Ocean Regime Shift
The system reversed in 1993.
Chiba, S. et al. 2006. Effects of decadal climate
change on zooplankton over the last 50 years in
the western subarctic North Pacific. Global
Change Biology 12 907-920.
42
Six Pragmatic Principles for Agriculture - 5

• Consider possible multiple stable states
• Ecosystems can not always get back to where
  they started before disturbance
• Map the resilience of agricultural systems
• Determine the critical disturbance factors

43
Multiple Stable States
Community B
Community A
Community C
Allison, H.E. Hobbs, R.J. (2006) Science and
policy in natural resource management
understanding system complexity. Cambridge
University Press, Cambridge. 241 pp.
44
Equilibrium States
Scheffer, M. Carpenter, S.R. 2003. Catastrophic
regime shifts in ecosystems linking theory to
observation. Trends in Ecology Evolution 18
648-656.
45
Six Pragmatic Principles for Agriculture - 6

• Expect on-going pest control problems
• Pest control is an arms-race
• Never underestimate the power or speed of
  evolutionary change
• Work with natural controls not against them

46
Resistance to Bt in Cabbage Looper
Rapid decline in resistance if no selection
Janmaat, A.F. Myers, J. 2003. Rapid evolution
and the cost of resistance to Bacillus
thuringiensis in greenhouse populations of
cabbage loopers, Trichoplusia ni. Proceedings of
the Royal Society of London, Series B, 270
2263-2270.
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Ecologically-Based Pest Management

• Understand the biology of the pests
• Kill, kill, kill. is not a strategy of
  management but a stop-gap measure
• Sustainable agriculture demands this of
  scientists, but the research is not easy and it
  is expensive

Singleton, G. R. et al. 2005. Integrated
management to reduce rodent damage to lowland
rice crops in Indonesia. Agriculture, Ecosystems
Environment 10775-82.
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Summary 1

• Agricultural monocultures are well designed for
  multiple ecological problems
• To solve these problems, it is useful to look at
  natural ecosystems and the rules by which they
  operate

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Summary 2

• If natural areas are not protected within
  agricultural landscapes, there will be a net
  loss of ecosystem services
• The retention of biodiversity is an essential
  component of sustainable agriculture

50
Summary 3

• We need monitoring indicators to tell us how
  well we are doing
• We need targets for all the elements in
  sustainable agriculture
• We must encourage agricultural scientists and
  ecologists to work together on these gigantic
  problems

51
Summary 4

• Keep the pieces (genetic, species)
• Keep the blueprints (reference ecosystems for
  comparison)
• Keep the ecosystem services (pollination, pest
  control.)