ECOSYSTEMS AND AGROECOSYSTEMS

6/09/2010

Definition

• Individual (species)• Population• Community• Ecosystem• Landscape

Individuals and Population

• No population exists as an isolated entity• Individuals not only interact among

themselves but also interact with other population individuals

• This interacting web of populations is called a community

• Population + community + environment = ecosystem

COMMUNITY

• Communities are groups of organisms (populations) that maintain persistent associations with each other.

• The members of a typical community include plants, animals, and other organisms that are biologically interdependent through predation, parasitism, and symbiosis.

• Ecology: is the scientific study of the interactions that determine the distribution and abundance of organisms.

• Ecosytem: The assemblages of individuals, communities, and physical environments.– Ex. Ponds, lakes, forests etc.

• Ecosystems are ultimate unit for study in ecology

• Life sytems: subdivision of ecosystems

Concept of Agroecosystem• Agriculture + ecosystem =Agroecosystem

• Any ecosystem largely created and maintained to satisfy a human want or need is called an agroecosystem

• Agroecological research is the idea that, by understanding ecological relationships and processes, agroecosystems can be manipulated to improve production and to produce more sustainably, with fewer negative environmental or social impacts and fewer external inputs

Difference between manipulated Agroecology and Natural Ecology

Six ways difference : • Maintenance at an early succession state• Monoculture• Crops generally planted in rows• Simplification of biodiversity• Plough which exposes soil to erosion• Use of genetically modified organisms and

artificially selected crops

• Semi-domesticated ecosystems that fall on a gradient between ecosystems that have experienced minimal human impact, and those under maximum human control.

• E.g.- Integrated pest management aims to control problematic pests through introduction of other species, not application of pesticides or herbicides to kill that pest. Method of intercropping.

• Elimination of unsustainable practices such as increasingly intensified pesticide use.

SUSTAINABLE AGROECOSYSTEMS

• Maintain their natural resource base.

• Rely on minimum artificial inputs from outside the farm system.

• Manage pests and diseases through internal regulating mechanisms

• Recover from the disturbances caused by cultivation and harvest

Interactions Among Ecosystems

– Destruction of ecosystems:• Natural to agricultural to urban succession.• Agricultural vs. natural – farmers concerned pests

will come out of the woods (not true).• Urban vs. natural – environmental losses• Urban vs. agricultural – concerned about pesticide

issues.

UrbanNat. Ag