Concepts of Agroecology and sustainability

1
Concepts of Agroecology and sustainability

• Dr Lina Al-Bitar, PhD
• CIHEAM/IAM-B

2

• Part 2
• Introduction to agroecology and Ecology
• Ecosystem and Agroecosystem
• Structure and functionning of ecosystem
• Difference between ecosystem and agroecosystem
• The environmental complex

3
Agro-ecology
Agroecolgy has become an important means of
designing and managing agroecosystems for
sustainability.
4
Agro-ecology
Agro, in Greek Agròs, means field.
Eco, in Greek oikos, means the home, the place
where we live.
Logòs, in Greek phylosophy, is the law of the
world, the metaphysical principle that animates
the matter.
Ecology is the science concerned with the
interrelationship of organisms and their
environments.
5
Ecology
It studies all that happens on the Earth.
Its aim is to study and understand reality as a
whole.
It has as object of study the ecosystem.
6
Ecosystem
A dynamic complex of plant, animal and
micro-organism communities and their non-living
environment acting as a functional unit.

• A unity that, through the continuous flow of
  solar energy that sustains it, is capable of
• Self-organization
• Self-control
• Self-maintainance
• Self-evolution

7
Levels of organization

• Organism
• Population
• Community
• Species diversity
• Dominance
• Vegetative structure
• Trophic structure
• Stability

8
Ecosystem functioning Energy flow
decomposers
9
Ecosystem functioning nutrients

• Needed for organism growth and development

• Nutrients cycle in ecosystems, constantly
  changing form, and moving from one component to
  another

• biogeochemical cycle
• - occur from the local to the global scale
• - Improve biotic and abiotic components
• - C, N, O, P and S are the most important.

10
Nitrogen cycle
phosphorus cycle
11
(No Transcript)
12
Ecosystem functionning mechanisms of population
regulation

• Environment adaptations

• predation

• interference

• mutualism
• Symbiosis
• parasitism

• competition
• Interspecific
• intraspecific

13
Ecosystem and Agro-ecosystem

• Ecosystem used for agricultural aims.

• Ecosystem modified in its physionomy with the
  introduction in space and time of new selected
  components.

14
Agro-ecosystem
Agroecosystems are domesticated ecosystems that
are in many basic ways intermediate between
natural ecosystems, such as grasslands and
forests on the one hand, and fabricated
ecosystems, such as cities on the other hand.
Agroecosystems are communities of plants and
animals interacting with their physical and
chemical environments that have been modified by
people to produce food, fibre, fuel and other
products for human consumption and processing.
15
They are solar powered as are natural ecosystems,
but differ in that
(1) the auxiliary energy sources that enhance
productivity are processed fuels (along with
animal and human labour) rather than natural
energies
(2) diversity is greatly reduced by human
management in order to maximize yield of specific
food or other products
(3) the dominant plants and animals are under
artificial rather than natural selection
(4) control is external and goal oriented rather
than internal via subsystem feedback as in
natural ecosystems.
16
Agroecosystem functionning
Solar Energy
Plant Biomass
harvest
Plant residues
Animal Biomass
dungs
Soil organic matter
manure
17
INPUT
Fossil stock
Natural energy flow
Auxiliary energy flow
Native Abundant For free clean
Imported Limited Expensive polluted
Agroecosystem farm
Environment (air, water, soil, organisms)
Market
OUTPUT
18

• Intensive Extensive
• (conventional) (sustainable, organic,
  traditional)
• Monocolture Polyculture
• Mechanization Animal traction, labour
• Intensive tillage no, minimum tillage
• Mineral Fertilization On-farm organic
  fertilization
• Chemical control Biological control
• Irrigation Storm water
• Selected varieties Native, Indigenous varieties

Agroecosystems
19
Comparison between natural ecosystems and
agroecosystems (Gliessman, 1997)
Natural Ecosystems Sustainable Agroecosystems Conventional agroecosystems
Production low Low/ medium high
Productivity medium medium/ high Low/ medium
Diversity high medium low
Resilience high medium low
Output stability medium Low/ medium high
Flexibility high medium low
Human interaction low medium high
Reliance on external inputs low medium high
Autonomy high high low
Sustainability high high low
20
The environmental complex
The environment is not a set of seperate
resources, but a complex of interacting resources
that need to be understood as part of a dynamic
system.

• The main factors are
• Light
• Temperature
• Water (in the soil and the atmosphere)
• Wind
• Soil and nutrients
• Fire
• Biotic factors

21
Autecology
Is the study of agroecosystems from a more
limited perspective that of the individual crop
organism in relation to its environment.
Solar radiation
Relative humidity
temperature
humans
Atm. composition
Associated animals
wind
Crop organism
Rainfall, irrigation
Associated plants
fire
Soil nutrients
Topography, latitude
Soil
Parent material
Gravity
The environmental complex (Gliessman, 2000)