1.4 Feeding Peoplep. 25-34

Productivity

The average amounts of new plant biomass produced each year per unit area.

Productivity of ecosystems

Productivity is influenced by many factors

Factors that can increase productivity

Add water and fertilizer to desertsVery expensive

Factors that can increase productivity.

Clear cutting rain forestIntroduce good farm plants and animals into rainforest conditions.Not a good idea.Disease, pests, weather fluctuations.

Food and Population Size

Canadians consume more calories and more animal products per day than others in the world. 80% of the Earth’s population consumes grains as primary source of nutrition.

Food and Compeitiors

Natural ecosystem – hundreds of species are interconnected. Agricultural – produces short, simple food chains, that link plants to people.

Factors that increase productivity.

MonocultureA single crop (wheat, corn or rice) is often grown on huge areas of land. How does monocultural affect populations of primary consumers?

Costs of monoculture – pests

Poisons and food chains

To keep pests from damaging crops, many farmers spray their fields with poisionous chemicals, called pesticides. The pesticides are designed to kill insects but not harm other animals, in small doses. Problems occurs when pesticides enter food chains and pass from one trophic level to another.

The DDT Story

DDT used during WWII to kill lice, fleas and mosquitoes.Persistant pesticide that can remain in the ecosystem for large periods of time.

The DDT Story

Used on crops to control damage caused by insect pests

The DDT StoryIn 1962 Rachel Carson published Silent SpringDDT restricted in Canada after 1969

The DDT Story

DDT is a great example of biological magnification.The concentration of chemical increases as you move up each trophic level in a food chain.

What you need to do now

Read p. 30 & 31 Do p. 32 # 1-9 and 11 Do p. 34 # 1-5