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

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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

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Agriculture38

The three-legged stool of sustainability

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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

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Agriculture40

Environmentally Sound

Preserves

the

quality of

soil,

water,

and air

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Agriculture41

Cooperates

with and

is modeled

on natural

systems

Environmentally SoundEnvironmentally Sound

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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.