Learning Goals Understand how modern agriculture practices have

Learning Goals: Understand how modern agriculture practices have led to the introduction of fertilizers & pesticides, and the effect this had on the environment and biodiversity Understand the different types of pesticides, and be able to provide examples of each Pose possible solutions to the problems caused by modern agricultural methods 1

Agricultural Methods, Pest Management and their effect on biodiversity and the environment 2

Recap Agriculture History human muscle power fossil fuel power • • Little genetic diversity can be detrimental if a new pest attacks the crop because entire crop is lost - leading to increased pesticide use No crop rotation depletes soil nutrients thus increasing fertilizer use 3

Nutrients in Soil • Primary soil nutrients often in short supply are Nitrogen, Phosphorus, and Potassium. – • Macronutrients - Elements required/used in large quantities. Removed after each harvest. Ex. Nitrogen, Potassium, Phosphorus Micronutrients - Chemical elements only required/used in very small quantities. Vitamins like Zinc 4

The Impact of Fertilizer – – Fertilizers replace soil nutrients extracted by plants. Problems: v 1) Contain nitrates that dissolve in the groundwater and runoff into our waterways v v At high levels, nitrates can poison humans, particularly children. Lower levels of nitrates can be deadly to amphibians. Can be released into the atmosphere as NITROGEN OXIDES which contribute to acid rain and climate change 5

• Problem with Fertilizer Use: 2) Eutrophication Groundwater with nitrates flows into lakes and streams causing: ALGAE BLOOMS: -cover the surface of the water so sunlight can’t reach far below reducing the ability of underwater plants to perform photosynthesis and produce oxygen. 6

SUMMARY OF FERTILIZER EFFECTS 7

Increasing Fertilizer Use 8

Pesticides • • • Pests referred to as target organisms. – Nontarget organisms are other organisms killed as an unwanted side effect. Persistent - Remain active for long periods, are fat soluble and remain in the fat tissue of humans and other animals. ie. DDT Non-persistent –more modern, break down quickly (thus are applied more often), are water soluble and can be excreted in urine. 9

Agricultural Chemical Use • • • Pesticide - Any chemical used to kill or control populations of unwanted fungi, plants, or animals (pests). – Can be subdivided into several categories based on the organisms they control. Insecticides - Control insect populations. – Raid, DEET Fungicides - Control fungal pests. Methylmercury Rodenticides - Control mice and rats. D Con Herbicides-Control plant pests(weeds). Round up(dandelions) Biocides - Control large variety of organisms. - DDT 10

Insecticides • Chlorinated Hydrocarbons - Complex, stable structure, long-lasting, persistent pesticides. – Effective for long periods after application. v Tend to accumulate in soil and animal bodies. Ø Affect many non-target organisms. – No longer used in many parts of the world. v Still used in many developing countries to protect crops and public health. 11

Herbicides v Weeds compete with crops for soil nutrients or are ‘unattractive’ in lawns Ø Traditional weed control methods are expensive in terms of time and energy. 12

Problems with Pesticide Use • Persistence - Persistent pesticides become attached to small soil particles and are easily moved by wind or water. – May be distributed throughout world from local applications. – Just because one country has banned them, does not mean they can’t end up in other areas 13

Fungicides and Rodenticides • • Fungicides are an important defense against spoilage of seeds and mature crops. – Methylmercury In some parts of the world, governments place a reward on rats because they can destroy agricultural crops. – Also carry diseases harmful to humans. v Rodenticides must be used with great care to prevent poisoning non-target organisms. 14

Problems with Pesticide Use • Bioaccumulation and Biomagnification – Bioaccumulation - Accumulating material within an organism’s body. v Many persistent pesticides are fat soluble and build up in fat tissues. – Biomagnification - Acquiring increasing levels of a substance in bodies of higher trophic-level organisms. v DDT, Mercury, PCBs Ø DDT banned in U. S. in early 1970 s. 15

Problems with Pesticide Use • Pesticide Resistance - Insecticides only kill susceptible individuals. – Most surviving individuals have characteristics that allowed them to tolerate the pesticide. v Survivors pass on genetic characteristics for tolerance. Ø Subsequent pesticide applications become less effective. 16

Problems with Pesticide Use • Effects on Non-Target Organisms - Most pesticides are not species specific, and kill beneficial species as well as pest species. – Many kill predator and parasitic insects that normally control pest insects. v May change population structure so that a species not previously a problem may become a serious pest. 17

Problems with Pesticide Use • Human Health Concerns – Acute poisoning during application. v WHO estimates between 1 million and 5 million acute pesticide poisonings annually. 18

Problems with Pesticide Use • • Perfect Pesticide: – Inexpensive – Only affect target organism – Break down quickly into harmless materials Newer pesticides have fewer drawbacks than early hard pesticides, but none are devoid of problems. 19

Solutions • Organic Agriculture – Originally, all farming was organic. v Animal manure and crop rotation provided soil nutrients. v Crop diversity prevented pest problems. v Manual labor controlled insects / weeds. – Some farmers are returning to organic farming due to chemical problems and costs. 20

Solutions • • Modifying Farming Practices – Crop Rotation (Plant a species like alfalfa that naturally brings Nitrogen back into the soil) Selective Use of Pesticides – Identification of precise time when pesticide application will have the greatest effect at the lowest possible dose. 21

Integrated Pest Management – Natural Predators v Aphids can be controlled with ladybugs v What problem does introducing a new organism into the ‘mix’ pose? 22

Learning Goals: DO WE: CAN WE: Understand how modern agriculture practices have led to the introduction of fertilizers & pesticides, and the effect this had on the environment and biodiversity? Understand the different types of pesticides, and be able to provide examples of each? Pose possible solutions to the problems caused by modern agricultural methods? 23