Month Day Lecture Activity Chap.

Nov. 21 Ecosystems II Services 56

26 Global C cycle 56

Dec. 3 Thinking ecologically I

5 Thinking ecologically II

Eco. literacy

10 Exam review

19 Final exam Here at 12:20 am

Agricultural production vs human populations

Factors driving increased food production

• New cultivars (breeds) of crops

Factors driving increased food production

• New cultivars (breeds) of crops

• Good cropland made better– Irrigation– Fertilizers– Pesticides– Mechanization

Factors driving increased food production

• New cultivars (breeds) of crops• Good cropland made better

– Irrigation– Fertilizers (N from fossil fuels)– Pesticides– Mechanization

• Marginal cropland put into cultivation– Irrigation– Fertilizers– Tillage

Energy use in agricultural production (in billions of Kcal)

Where Total energy

Energy per hectare

Energy per capita

Developed Nations 1108 5.92 43.7

North America 511 4.83 79.6

Developing Nations 221 0.53 2.6

Energy use in US corn production

1000

10,000

1700 19901950Year

Ene

rgy

inpu

t (x

100

0 K

cal/h

a)

Food versus fuel

Food energy

Fuel energy

Bulk production 1 2

Edible production 1 3

Shipping 1 3

Processing 1 3

Preparing 1 2

Modern agriculture is subsidized by fossil fuels

1 unit food energy = 12 units fuel energy

Modern agriculture is subsidized by fossil fuels

1 unit food energy = 12 units fuel energy

Think back to the trophic pyramid...

Does negative energy transfer efficiency make sense?

Agricultural carbon cycle does not balance!

1 unit food energy = x g C, so took y g C out of the atmosphere

1 unit fuel energy = x g C, so put z g of C (CO2) into the atmosphere

Problems of modern agriculture

Practice

Problem addressed Problem created

Mechanization Labor inefficiency

erosion

negative C balance

energy dependency

larger farms

fewer farmers

loss of farm culture

Problems of modern agriculture

Practice

Problem addressed Problem created

Inorganic N fertilizers

Crop yield water pollution

increased pests

greenhouse gas emissions (N2O)

energy dependency

Problems of modern agriculture

Practice

Problem addressed Problem created

Pesticides Crop loss new pests

resistant pests

water and soil pollution

human poisoning

energy dependency

Problems of modern agriculture

Practice

Problem addressed Problem created

Hybrids and genetically narrow crops

Crop yield pest problems

loss of local adaptations

chemical dependency

dependency on external seed source

Solutions...

• Erosion from mechanical tillage– No till or low till systems– Perennial crops– Field layouts– Controlled irrigation

Solutions...

• Fertilizer pollution of water and atmosphere– Keep litter on the fields– Increased use of organic fertilizers– Type and timing of fertilizer application

Solutions...

• Pesticide resistant insects, pollution and human poisoning– Integrated pest management– “Smart” application of pesticides– Changes in consumer expectations– Genetic engineering of “natural” pesticide

resistance

Solutions...

• Loss of genetic diversity– “Seed saving” – Crop diversification– Consumer demand

Solutions...

• Fossil fuel dependency– Buy local– Buy less processed foods– Eat lower on the food chain– Buy organic (?)