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ECOLOGICAL PRINCIPLES IN FARM DESIGN:farming in ”nature’s image”
RELEVANT LITERATURE • Gliessman S 2004 Agroecology and agroecosystems. In: Agroecosystems Analysis, D. Rickerl and C. Francis, editors. American Society of Agronomy, Madison, Wisconsin, USA. 43: 19–29 [book used in summer travel class, Iowa State U] • Gliessman S 1998 Agroecology: ecological processes in sustainable agriculture. Lewis Publishers, Boca Raton, Florida; also London, New York, Washington [most popular US text] • Gliessman S 2007 Agroecology: the ecology of sustainable food systems. Lewis Publishers, CRC Press, Boca Raton, Florida; also London, New York, Washington [new edition of same text] • Soule J And J Piper 1991 Farming in nature’s image: an ecological approach to agriculture. Island Press, Washington, DC [original book on Land Institute research and perspective] ECOLOGICAL PRINCIPLES IN FARM DESIGN
Conditions of sustainability Indicators of sustainability Socio-economic parameters Ecological parameters Agroecosystem structure and function Socio-economic components Ecological components Agroecosystem context and foundation Socio-economic Natural resources (Adapted from Gliessmann 1998) WHY PAY ATTENTION TO ECOLOGICAL PRINCIPLES? • ecological structures and functions are building block on which economic and social sustainability depend ECOLOGICAL PRINCIPLES IN FARM DESIGN
KNOWLEDGE BASE • Natural ecosystems • Reference systems for understanding • generic ecological structures and functions: generalizable principles • ecological basis for sustainability in a particular location: each farm is unique • Traditional (local or indigenous) ecosystems having passed the test of time • Examples of sustainable co-evolution of human culture and its local environment ECOLOGICAL PRINCIPLES IN FARM DESIGN
ECOSYSTEM • a functional system of complementary relations between living organisms and their environment, delimited by arbitrarily chosen boundaries, which in space and time appears to maintain a steady yet dynamic equilibrium (Odum 1996; Gliessman 1998) ECOLOGICAL PRINCIPLES IN FARM DESIGN
ECOLOGICAL PRINCIPLES OF NATURAL ECOSYSTEMS: ENERGY • Flows as a result of complex sets of trophic interactions • Certain amounts are dissipated at different stages along the food chain [10:1 ratio across trophic levels] • Greatest amount moving along the detritus pathway (Odum, 1971) • Energy sources in natural ecosystems are renewable ECOLOGICAL PRINCIPLES IN FARM DESIGN
ECOLOGICAL PRINCIPLES OF NATURAL ECOSYSTEMS .....NUTRIENTS • Small inputs through hydrobiogeochemical processes; e.g., • precipitation • N2 fixation • weathering of minerals • Internal circulation through complex sets of interconnected cycles • Most often bound in organic matter (Borman and Likens 1967) • Biological components are very important flow rate regulators, e.g., • decomposers • mycorrhiza • plants • In mature (climax) ecosystems, there are minimal losses, which are in balance with the small inputs ECOLOGICAL PRINCIPLES IN FARM DESIGN
Early agriculture (till 18th – mid-19th Century) Industrial agriculture (since mid-20th century) Urbanising agriculture (till mid-20th century) Humans Humans Humans Animals Animals Animals Plants Plants Plants (From Magdoff et al. 1997) ...NUTRIENTS: Spatial relationships of the trophic pyramid ECOLOGICAL PRINCIPLES IN FARM DESIGN
ECOLOGICAL PRINCIPLES OF NATURAL ECOSYSTEMS.....DIVERSITY • Succession through time tends toward establishment of the most complex structure and function biologically possible within the limits set by the environment • Diversification of • trophic interactions • niches • Maximum exploitation of available resources and niches • Control of population levels of the various organisms • A degree of resistance to all but very damaging perturbations,i.e., fluctuation around a dynamic equilibrium, • the fluctuations often causing increased diversity and productivity ECOLOGICAL PRINCIPLES IN FARM DESIGN
.....DIVERSITY ECOLOGICAL PRINCIPLES IN FARM DESIGN
SUMMARY: ECOLOGICAL PRINCIPLES • How did physical & biological structure relate to the functions you observed on project farms? • What were the major energy sources on your project farms? What were major losses of energy? • List and describe principle nutrient sources on your project farms. List also major nutrient losses. • What elements and functions of natural ecosystems were operating on project farms? • What were the major types of biodiversity observed on the farms you visited? ECOLOGICAL PRINCIPLES IN FARM DESIGN
SUMMARY: MORE QUESTIONS--ECOLOGICAL PRINCIPLES • How would you apply ecological structure and function to design a diverse agroecosystem with crops & animals? • What strategies would you employ to increase efficiency of energy use and minimize loss from the farm? • In what ways could you increase nutrient cycling and thus reduce productions costs on the farm? • What parallels do you see between the role of a keystone predator in the natural ecosystem and the role of people in agroecosystems? ECOLOGICAL PRINCIPLES IN FARM DESIGN