1. Agroecology. Ecological understanding of farming systems. Ben-Gurion
University of the Negev
Ben-Gurion University of the Negev
Agroecology Ecological understanding of farming systems 1. Introduction • Definitions Dr. Bertrand Boeken The Wyler Dept. of Dryland Agriculture Jacob Blaustein Institute for Desert Research Ben-Gurion University of the Negev Sede Boqer Campus 84990 Israel Tel. office 08-659 6893 Tel. home 08-623 4782 © BBoeken 2005-16
• Contexts • Perspectives • History of agriculture
[email protected] http://www.bgu.ac.il/desert_agriculture/Agroecology/
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Agroecology - definitions Gliessman 2000: “The application of ecological concepts and principles to the design and management of sustainable farming systems”
Understanding (Science) Practice (Technology)
Object Goal and Motivation What is sustainability?
Limited to a subset of farming systems (i.e., not the unsustainable ones)
How does sustainability vary? What makes a farming system sustainable? Is sustainability always attainable?
→ Agroecology as agricultural practice 2
Agroecology - definitions Understanding (Science)
B. Boeken, this course: The application of ecological concepts and principles to farming systems Ecological processes associated with farming
All agro-systems • Conventional, traditional and alternative agriculture
• Trophic structure
• Crop and animal production
• Flows of energy and materials (water, nutrients, carbon)
• Development through time
• Landscape and scale • Population dynamics of organisms • Natural selection and co-evolution • Biodiversity of biotic communities
→ Agroecology as a scientific discipline Wezel A. et al. 2009. Agron. Sustain. Dev. 29 (2009) 503–515 (www.agronomy-journal.org) Bensin B.M.1930. Int. Rev. Agr. Mo. Bull. Agr. Sci. Pract. (Rome) 21, 277–284.
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Agroecosystems - context Material human requirements • • • • • • • •
Water, air Food Fiber Fodder Fuel Shelter Space Goods
Human activities for food production • • • • • •
Hunting Gathering Fishing Grazing Farming Bio-industry
www.worldfuturefund.org
Human land-use • • • • •
Cropland Rangeland Woodland Urban/industrial Nature 4
www.worldfuturefund.org 5
Agroecosystems: perspectives • Social • Ecological • Biological • Technical • Historical http://www.worldisround.com
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Social perspectives • • • • • • •
Sociology Economy Politics Culture Religion Heritage Education www.whitehouse.gov 7
Ecological perspectives • Energy and resource flows • Trophic structure
Processes within agro-ecosystems
• Biodiversity
• • • •
• Population dynamics • Natural selection • Animal behaviour
Energy, resource flows Crop plant performance Biotic community dynamics Soil processes
Relationships with surrounding ecosystems
• Landscape dynamics • Spatial relationships:
• • • •
Agro-ecosystems
Resource flows from outside Predators, pests and weed invasion Export of plant and animal products Leakage of water, nutrients, agro-chemicals
Relationships between agro-ecosystems and the ‘rest of the world’
Natural ecosystems
• • • • •
Resource subsidies Introduction of invasive species Export of plant and animal products Pollution Global climate change
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Biological perspectives • • • •
Physiology and biochemistry Genetics, genomics Phytopathology Soil microbiology
www.soils.agri.umn.edu
www.ncgbc.org
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Technical perspectives • Irrigation • Soil preparation • Planting and sowing
www.opico.com
• Fertilizer application • Pest control • Harvesting www.rec.udel.edu 10
Historical perspectives Time-line (yrs) Archaic Homo sapiens
-250,000
hunting-gathering, nomadic
Prehistoric
-15,000
domesticated plants and grazers
Ancient
-5,000
soil cultivation, irrigation
Medieval
-1,500
deep plowing, manure, selection, profit
Modern
-200
scientific approach
Contemporary
-60
industrialization, alternative approaches, ecological sustainability (?)
Increasing trends • Global and local human population size • Control over food production • Dependence on technology, transport 11
Early human foraging 250,000 years ago • Nomadic hunter-gatherers • Small communities in open landscapes • Human evolution and early cultural development http://www.archaeologyinfo.com/homosapiens.htm
Social structure: clan/family groups Food: grains, nuts, berries, tubers, vertebrates, insects Problems: predators, resource depletion, adverse selection, rival clans Innovations: clothing, domestication of dogs 12
Adverse selection Gathering of wild cereal grain • Normal retention frequency distribution • People collect seeds remaining on the plants • Moves population mean to genotypes with lower retention
www.flickr.com
• In short time local populations become costlier to collect
Harvested
Frequency
Frequency
Assumptions
Seed retention
Seed retention
• Essential or important food source • Abundant population • No overharvesting by reducing abundance (no seed limitation of recruitment)
Consequences (Based on optimal foraging decisions by humans) • Diversity of food sources (“prey switching”) • Migration (nomadism)
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Prehistoric agriculture Started 15,000 years ago • Small semi-sedentary communities • Stone tools • Early agriculture • Early art www.sanford-artedventures.com
Social structure: larger clan/family groups Food: wild animals and plants, local produce Problems: predators, resource depletion, rival clans Innovations: tools, domestication of grains, herbivores 14
Domestication Cultivation of cereal grain • Wild populations have normal retention frequency distribution • Planting of grains remaining in ears • Crop population mean with higher retention
www.geog.ucsb.edu
Harvested
Seed retention
Frequency
Frequency
• Crop populations become more profitable to collect
Seed retention
Consequences • • • •
More control over food supply and quality Larger, sedentary human populations Reliance on resources, technology and knowledge Danger of resource depletion (and over-harvesting in non-seed crops)
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Ancient agriculture Started 5,000 years ago • Larger villages, cities • Large-scale agriculture • Metal tools • Soil cultivation, irrigation • Food storage www.touregypt.net
• Burocracy
Social structure: large non-family groups Food: local produce, storage Problems: predators, resource depletion, rival clans Innovations: domestication of vegetables, fruit trees, cats 16
Medieval agriculture Started 1,500 years ago • Feudal relations • Large cities, manors • Large-scale agriculture • Sustenance and profit • Plowing, fertilization Social structure: feudal (serfdom) Food: local produce, storage, import Problems: food shortage, desease http://medieval.ucdavis.edu
Innovations: selection, work differentiation 17
Modern agriculture Started 200 years ago • Population increase • Land development • Production maximization • Mechanization • Profit www.stolaf.edu
Social structure: family business Food: local produce, storage, import, industrial processing Problems: pests, pollution, subsidies, capital investment, scale enlargement, uniformity Innovations: science-based, hybrid crops
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Crop trait selection Selection for desired phenotypic traits • Crop diversity • Market value • Genotypes adapted to different conditions http://www.doctortee.com/
B
Trait 2
Trait 2
B
(c)
A
A B
B A
1 2 Environment
1 2 Environment
(d)
Trait 1
Genotypes
• Trade-off between the traits (c) • Physical/physiological trade-offs: Limitation of selection (d)
(b)
A
Growth
• Reaction norms for 2 phenotypic traits (a,b)
(a) Trait 1
Genotype-environment interactions (G×E)
(temperature, resource availability, seasonality, etc.)
Dry
Soil moisture
Wet
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Contemporary agriculture Started ca. 60 years ago • Population increase • Reduced natural area • Production maximization • Globalization encarta.msn.com
• Profit, monopoly
Social structure: private and corporate business Food: import/export, industrial processing Problems: pests, pollution, subsidies, capital investment, encroachment on nature, global warming Innovations: bio-industry, precision agriculture, genetic engineering, alternative life-styles
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