1. Chapter 11: Agriculture, Aquaculture and the Environment

2. Overview An Ecological Perspective on Agriculture
Can We Feed The World?
What We Grow on the Land
Soils
Controlling Pests
The Future of Agriculture
Genetically Modified Food: Biotechnology, Farming, and Environment
Aquaculture

4. Agroecosystem
Ecological succession stopped to keep the agroecosystem in an early-successional state
Focus on Monoculture
Monoculture - large areas planted with a single species
Counteracted by crop rotation
Crops planted in neat rows and fields
Makes crops vulnerable to pests

5. Agroecosystem
Farming greatly simplifies biological diversity and food chains
Plowing is unlike any natural soil disturbance
Nothing in nature repeatedly and regularly turns over the soil to a specific depth
Genetic modification of crops

6. Can We Feed the World?
To answer this we must understand how crops grow and how productive they can be
Most viable of human activities but is it sustainable?
Regions farmed for thousands of years
Farming changed local ecosystems

8. Can We Feed the World?
History of agriculture is a series of human attempts to overcome environmental limitations and problems.
Each solution creates new problems
Should expect some side effects
Multiple pressures on agricultural land

10. Can We Feed the World?
As population grows, the production of agriculture must grow
Food supply is already inadequate for some peoples
Increasingly marginal land will need to be put into production
Food supply also greatly influenced by social disruptions and social attitudes

11. How We Starve People “starve” in two ways Undernourishment
Lack of sufficient calories in available food
Manifests as famine
Malnourishment
Lack of specific chemical components of food, such as protein, vitamins, or other essential chemical elements

12. How We Starve Undernourishment
Marasmus – progressive emaciation caused by lack of protein and calories
Kwashiorkor – a lack of sufficient protein in the diet
Chronic hunger – enough food to stay alive but can not live satisfactory or productive lives

13. How We Starve
World food production must provide adequate nutritional quality and quantity.
Food emergencies affected 34 countries worldwide at the end of 20th century
Africa has the most acute food shortages
Food distribution major problem
World food aid does not meet all the caloric need of people
Best solution is to increase local production

16. What We Grow on the Land Crops
Of Earth’s ½ million plant species, only about 3,000 are agricultural crops
150 species cultivated on large scale
Most of world’s food provided by 14 crop species
6 provide 80% of the total calories

18. Livestock Forage- crops grown for domestic animals
In US 14 million areas of alfalfa
Domestic animals include
14 billion chickens
1.3 million cattle
~1 billion each sheep, ducks and pigs
700 million goats
160 million water buffalo
18 million camels

19. Livestock Rangeland Pasture Large world market in small grain crops
Provides food for grazing and browsing animals w/o plowing and planting
Pasture
Plowed, planted and harvested to provide forage
Large world market in small grain crops
See next slide

21. Livestock- effect on environment
About half the earth’s land area is used as rangeland
Most is easily damaged by grazing (drought)
Much of the rangeland is overgrazed
Grazing cattle trample stream banks and release waste into streams

22. Soils Soils are not just “dirt”
Key to life on land
Earth modified over time by physical, chemical and biological processes into a series of layers called horizons
O horizon - organic layer on top of soil
A (& E in some soils) horizon- upper horizon
B horizon - zone of accumulation
C horizon - most similar to parent material

24. Soils Soil fertility Soil Drainage
Capacity of a soil to supply nutrients necessary for plant growth
Geologically younger soils are typically more fertile
Soil Drainage
Soils with high clay content hold water well
Soil with high sand content drain very well

25. Restoring Our Soils Soil erosion has decreased 40% in US
Due to better farming practices
Use of chemical (artificial) fertilizers increased soil fertility in 20th century
Use of phosphorus (mined and in guano) in fertilizers increased soil fertility

26. Limiting Factors
Crops require 20 chemical elements at the right amount at the right time of year
Macronutrients
micronutrients
High-quality agricultural soil has
All the chemical elements required for plants
A physical structure that lets air and water move freely
Retains water well
Mixture of soil particle size

27. Limiting Factors Liebig’s Law
Single factor determines the growth and therefore the presence of a species
Growth of a plant is affected by one limiting factor at a time

28. Limiting Factors Two elements may have a synergistic effect
A change in the availability of one resource affects the response of an organism to some other resource.
Chemical elements may become toxic when levels are to high

29. Controlling Pests Pests are undesirable Agricultural pests include:
Competitors, parasites, and predators
Agricultural pests include:
Insects
Nematodes
Bacterial and viral diseases
Weeds
Vertebrates
Loss can be large
Estimated at 1/3 of potential harvest and 1/10 of the harvested crop

30. Controlling Pests
Farms are maintained in early stage of ecological succession and enriched by fertilizers and water
Great area for crops
Great area for early-successional plants (weeds)
Weeds compete for all resources
Light, water,nutrients, and space to grow

31. Pesticides- History Stage 1 Broad Spectrum Inorganic Toxins
Search for chemicals that would reduce abundance of pests
Goal was narrow-spectrum (species-specific), but most were broad-spectrum
Ex: Arsenic, toxic to all life
Killed pest and beneficial organisms

32. Pesticides- History
Stage 2: Petroleum based sprays and natural plant chemicals
1930’s
Ex: nicotine

33. Pesticides- History Stage 3: Artificial Organic Compounds
DDT, broad-spectrum
Aldrin and dieldrin used to control termites
Problems
Toxic to humans, has been found in breast milk
Secondary Outbreaks
Pests develop resistance

35. Pesticides- History
Stage 4: Return to biological and ecological knowledge
IPM - Integrated Pest Management
Goal is to reduce use of artificial pesticides
Biological control- the use of biological predators and parasites to control pests
Bacillus thuringiensis (BT) - Proved safe and effective

36. Integrated Pest Management
IPM uses a combination of methods
Biological control
Chemical pesticides
Methods of planting crops (mixed fields)
Goal can be control not elimination of pest
Economically makes sense
Does less damage to ecosystem, soil, water and air

37. Biological Control Other biological control agents
Small wasps that parasitize caterpillars
Both effective and narrow spectrum
Ladybugs
Sex pheromones (chemicals released to attract opposite sex) used as bait in traps

39. The Future of Agriculture
Three major technological approaches to agriculture
Modern mechanized agriculture
Resource-based agriculture
Organic food production
Bioengineering

40. How can crop production keep up with population growth?
Increased production per acre
Technology driven
New Crops and Hybrids
New or yet unused plants could do well in poorer agricultural soil
Green Revolution

41. The Green Revolution
Name attached to the post WWII programs that have led to the development of
new strain of crops w/ higher yield
better resistance to disease
or better ability to grow under poor conditions

42. How can crop production keep up with population growth?
Better irrigation techniques
Could improve crop yield and reduce overall water use
Drip irrigation
Hydroponics
Eating Lower on Food Chain
Same area of land could produce 10–100 times more vegetation than meat per year

43. How can crop production keep up with population growth?
Organic faming
Three qualities
More like nature ecosystem than monoculture
Minimizes negative environmental impacts
The food that results does not contain artificial compounds
One of the fastest growing sectors in US agriculture

44. Genetically Modified Food
Scientist have been able to transfer specific genetic characteristics from one individual to another, from one population to another, and from one species to another.
Genetic engineering in agriculture involves several practices
Faster and more efficient ways to develop hybrids
Introduction of the terminator gene
Transfer of genetic properties from widely divergent kinds of life

45. Genetically Modified Food
Considerable interest in developing crops
With entirely new characteristics
E.g. nitrogen fixation
With tolerance of drought, cold, heat and toxic chemical elements.

46. Genetically Modified Crops
Three methods
1. Faster and more efficient development of new hybrids
2. Introduction of the “terminator gene”
3. Transfer of genetic properties from widely divergent kinds of life

47. New Hybrids
From an environmental perspective, genetic engineering to develop hybrids w/in a species is likely to be a benign as the development of agricultural hybrids has been w/ conventional methods.
Concern that genetic modification may produce
“superhybrids”
Could become pest or transfer genes to closely related weeds

48. The Terminator Gene Makes seeds from a crop sterile Critics note
Done for environmental and economic reasons
Prevents a gmo from spreading
Protects the market for the corporation that developed it
Critics note
Farmer’s in poor nations must be able to grow next years crops from their own seeds

49. Transfer of Genes Genes transfer from one major life form to another
Most likely to have negative and undesirable impacts
E.g., Bacillus thuringiensis
Produce toxin that kills caterpillars
Gene identified and transferred to corn
Engineered corn now produces its own pesticide

50. BT corn contains its own
pesticide in every cell of
the plant.
Bacillus thuringiensis bacteria
(a natural pecticide). The gene
that caused the pecticide (BT)
was placed in corn through
genetic engineering.
Pollen from the BT corn is
also toxic and when it lands
on milkweed, monarch
butterflies that eat the
milkweed may die.

51. Transfer of Genes
Bt plants thought to be a constructive step in pest control
No longer need to spray pesticide
Bt plants produce toxin in all cells
Even in pollen that can spread
Monarch butterflies that eat pollen may die

52. Transfer of Genes
Much concern worldwide about the political, social and environmental effects of genetic modification of crops.

53. Aquaculture Most marine and freshwater food obtained by hunting
Not sustainable
Aquaculture- the farming of food in aquatic habitats
Important protein source

54. Aquaculture Extremely productive on a per-area basis
Flowing water brings food into the pond from outside
Can exploit multiple niches in the pond
May be able to utilize waste products (treated sewage)
Mariculture - the farming of ocean fish.
Also increasing production of oysters and mussels