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Global Food Global Food Supplies & Natural Supplies & Natural
ResourcesResources
What do humans use and consume from
ecosystems? __________________________________________
Human harvesting activities impact natural resources such as: air, water, & soil
As the human population increases, productivity of natural and cultivated ecosystems is threatened by our demand --- how can we feed, clothe, and shelter ourselves and provide energy for our activities without destroying the environment that provides it?
How can we manage ecosystems so that they are productive & sustainable?
Examples of Products Harvested from Natural
EcosystemsForest Products Lumber, fuelwood, pulp for
paper & fiberboard, food products (nuts, tropical fruits, maple syrup, etc.)
Products of prairies, savannas, & deserts
Furs and hides of animals, tusks, food (deer, kangaroo, ostrich eggs), pharmaceuticals
Products from aquatic ecosystems
Fish and shellfish, fishmeal (animal feed and fertilizer), whale oil
Examples of Products from Cultivated
Ecosystems
Which products are harvested from both natural & cultivated
systems?
Give advantages & disadvantages of
harvesting products from a cultivated
system
Ecologists & Productivity
Concerned with the flow of matter & energy through different parts of the ecosystem
Sun = energy source in almost all natural ecosystems; plants capture ~1% of solar energy through photosynthesis and fix the energy in organic compounds. Some compounds are used by plants to carry out their metabolism and some becomes part of the plant
Ecologists & Productivity
The rate at which organic matter is being fixed in an ecosystem through photosynthesis = gross primary productivity
Not all of the organic matter will become available to the rest of the food web, as some of it is used by plants. What remains = net primary productivity (similar to paycheck after taxes)
Estimated Net Primary Productivity
Biome Average Net Primary Productivity (kg/square
meter per year)
Tropical ForestTemperate ForestNorthern Coniferous ForestShrub landGrasslandSavannaDesertTundra & Mountain zonesWetlands (marshes & swamps)
1.81.20.80.60.50.70.10.12.5
Agricultural land 0.1 – 4.0 *depends on crop
Which biomes appear to be the most productive?
Which biomes appear to be the least productive?
What reasons can you give for the high productivity of estuaries compared to that of the open ocean?
What kind of climate is found in the two most productive terrestrial biomes?
What kind of climate is found in the two least productive terrestrial biomes?
What conclusions can you draw, if any, about the relationship between climate & productivity?
Net Productivity & Biomass
The net productivity of the primary producers in an ecosystem is a major factor in determining the carrying capacities of other species in that system
Plant biomass is the total amount of organic matter in plants at any one moment
Net productivity is a measurement of how much biomass is being added over a period of time
Rate of Decomposition
Cycles of matter are also important when studying the productivity of an ecosystem
Ecologists are interested in the distribution of elements such as: oxygen, carbon, nitrogen, and phosphorous throughout the system.
At times, these elements may be present in inorganic substances such as salt; at other times they are parts of organic matter
The decomposers play an important role in how these elements are distributed
Rate of Decomposition
Decomposers are the organisms that break down dead plant & animal matter, eventually reducing them to compounds that are usable by living plants
Examples include: soil dwellers such as earthworms, certain beetles, insect larvae, and numerous fungi & bacteria
The rate of decay in an ecosystem is an important factor in productivity
Rate of Decomposition
Decomposition rates are affected by variables such as:
-erosion of topsoil (carries away decomposers)
-climate (decomposers inactive during cold)
Farmers & Productivity
Farmers view productivity in terms of yield; yield = the amount of salable crop that can be obtained from a field (this is closely related to biomass)
How do yield & biomass differ?
Ecologists are interested in what limits productivity in an ecosystem whereas farmers are likely to be more interested in overcoming limits
Farmers add energy to the ecosystem in order to obtain a higher crop yield
Farmers & Productivity
Energy inputs in agricultural systems are required during:
-cultivation
-irrigation
-fertilization
-insect & weed control
What is the energy source for the inputs listed above?
Energy inputs increase yields but if the cost of inputs is greater than that of outputs, the farmer will not realize a profit and must go into debt
The Green Revolution A planned international effort to eliminate
hunger by improving crop performance
This period of increased productivity began in the 1950’s; the movement to increase yields used:
-new crop cultivars such as more highly productive strains of wheat & rice
-mechanization
-pesticides
-fertilizers
-irrigation
Dr. Norman Borlaug
Considered the Father of the Green Revolution, a U.S. Plant pathologist/breeder
Worked in the international maize & wheat improvement center in Mexico & doubled the amount of wheat Mexico was producing; went on to work in India, Pakistan, Asia & Africa
Won a Nobel Peace Prize in 1970
The Green Revolution Credited with feeding much of the world’s
population in the last few decades – still considered by many to be the only hope of feeding the world’s growing population
The Green Revolution There are problems:
-the rapid increase in yields is diminishing
-population is still on the rise
-modern practices have caused many environmental problems and increased the cost of production
Controversy abounds - today, biotechnology is leading the 2nd phase of the Green Revolution [we will address this later]
The Green Revolutionhttp://www.livinghistoryfarm.org/farminginthe50s/crops_13.html
Clip from Dr. Borlaug re: organic farming & criticism of green revolution
Sustainability in Cultivated Ecosystems Agricultural ecosystems differ from natural
ecosystems
In the past, humans hunted & gathered food from natural ecosystems, this required a lot of time spent on getting food & a lot of land to supply enough food for one person
The shift to agriculture meant more work on less land but the increased productivity enabled a few to feed themselves & many others
Sustainability in Cultivated Ecosystems Agricultural systems generally have a high
productivity but a low sustainability – the high energy inputs required can be too expensive for farmers to maintain
Agricultural practices, over time can lead to erosion or exhaustion of the soil
-plowing & tilling = vulnerability to soil erosion
-exposure to wind & rain = erosion &/or leaching
-annual crops do not have root systems capable of holding the soil
Sustainability in Cultivated Ecosystems Many agricultural systems focus on a single
crop (monoculture), which tends to be more profitable for the farmer but does limit sustainability
-single crops tend to speed up depletion of soil nutrients
-single crops are vulnerable to diseases & pests
ex: Irish Potato Famine
How Can Agricultural Systems Be Managed
so That They Are More Sustainable?
Integrated Pest Management (IPM)
A general philosophy of safe & effective pest control that uses several different methods of control to reduce the population of a particular pest
Involves identifying & understanding each pest, its life cycle, breeding sites, and density threshold (# of pests per area that can be tolerated without overall crop damage) & selecting remedies that address the specific pest problem
Diversity Producing several crops (may be combined
with livestock production)
Crop diversity can improve soil health & prevent devastation by a single pest or disease
When livestock & crops are both raised, they can provide inputs for one another ex: sow manure fertilizes sorghum & sorghum can be used to feed cattle
Alternative Tillage Methods
In no-tillage farming, the old crop is left in the field to form mulch (covering of organic matter) which reduces water loss, soil erosion, & weed growth
Reduced Use of Water
Drip irrigation lines are hoses at or under the ground which deliver water directly to crop roots = reduced water loss from evaporation
Rainwater recovery systems
Selection of drought-resistant crops
Composting The use of animal manure, crop residues,
tree clippings, & other organic material to make compost, which tends to be laden with beneficial microbes & plant nutrients
Sustainability in Natural Ecosystems
Natural Ecosystems tend to be stable due to:
-biological communities that remain fairly constant in their makeup = stable populations
-an abundance of perennial species
-relatively high species diversity
Harvesting of Natural Resources
Renewable resources should last indefinitely because they can be replaced through natural processes Ex: trees, fish, wildlife, fresh water, clean air, fertile soil, etc.
Renewable resources may not last indefinitely due to depletion or degradation Ex: pollution, deforestation, removal of water faster than it is replaced by natural processes
Summary The availability of food supplies & natural
resources is a global matter
Past methods of farming have been very productive but do not appear to be sustainable over a long period of time; farmers may have to think more like ecologists and focus on the flow of matter and energy through the system
The harvesting of natural resources also requires attention to sustainability – the methods by and rate at which resources are harvested may need regulation
Adapted from: CORD: Community of Life
Apr 21, 2023Toward a Sustainable
Agriculture36
What is Sustainable Agriculture?
“…a journey, not a destination” Iowa
Farmer
Apr 21, 2023Toward a Sustainable
Agriculture37
Sustainable Agriculture
“…an integrated system of plant and animal production practices…that will
satisfy human food and fiber needs
enhance environmental quality
make the most efficient use of
nonrenewable resources
sustain economic viability
enhance quality of life.”
1990 Farm Bill
Apr 21, 2023Toward a Sustainable
Agriculture38
The three-legged stool of sustainability
Apr 21, 2023Toward a Sustainable
Agriculture39
Economically sustainable
Provides a secure living for farm families
Provides a secure living to other workers in the food system
Provides access to good food for all
Apr 21, 2023Toward a Sustainable
Agriculture40
Environmentally Sound
Preserves
the
quality of
soil,
water,
and air
Apr 21, 2023Toward a Sustainable
Agriculture41
Cooperates
with and
is modeled
on natural
systems
Environmentally SoundEnvironmentally Sound
Apr 21, 2023Toward a Sustainable
Agriculture42
Socially sustainable
Good for families
Supports communities
Fair to all involved
Where are we?What are the
Strengths
and
Weaknesses
of our current agricultural system?
Successes abundant food supply in the developed world
fresh fruits and vegetables available year-round
cheap food
luxury foods such as coffee, tea, chocolate, and spices easily available around the world
effective food preservation technologies (refrigeration, freezing, canning, packaging)
convenience foods
mechanization produces high labor efficiency
improvements in soil conservation
availability of agricultural inputs for quick solutions to production problems
Problems continuing soil loss
food safety concerns (mad cow disease, food poisoning outbreaks, antibiotic resistance, toxins and pesticides)
water pollution, air pollution (& odors), habitat loss, water depletion
continuing hunger – and rise of obesity
failing farms, economic uncertainty and stress
declining communities
farm accidents, chronic diseases linked to agricultural chemicals
reliance on fossil fuels, global warming
farmland loss to development, ugly countryside
difficulty of starting in farming
Conclusion Agriculture has accomplished much
There are still many problems to solve, both old and new
Sustainable agriculture is about trying to solve these problems – without creating new ones.