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 (?)