Post on 26-Dec-2015
Will there be enough food??
With human population growing and much of the world’s arable land being used, how will we keep pace with providing enough food for everyone??
Thomas Malthus: Population increases at
an exponential rate, while food supplies grow arithmetically. Basically, we’re doomed !!
We have enhanced the productivity of our
cultivated lands. – more produce, using the same amount of land.
Scientific and technological advances in agriculture. OUTCOME : FOOD PRODUCTION HAS KEPT
PACE WITH THE POPULATION GROWTH
Technology !!!!
How much of the Earth’s surface can be used for agriculture?
Limiting factors: water, temp, topography, climate, soil quality and available technologies
Earth’s Land Resources
All chemicals present, required for plant
growth Physical structure that lets air and water move
freely Retains water well High organic content Mixture of sediment particle sizes
Small – retains water Large – aerates soil
What makes high quality Agricultural Soil?
Liebig’s Law of the Minimum: The idea that
some single factor determines the growth and , therefore, the presence of a species.
“The growth of a plant is affected by one limiting factor at a time – the one whose availability is the least in comparison to the needs of the plant”
Different crops require different soilsRarely does soil have everything a crop needs
Usually there is 1 limiting factor
What do we grow?
500,000 plant species
3000 used in agriculture Crops
150 cultivated on lg. scale
200 sp. Grown in US 14 sp. Provide most
of the worlds food
Crops and Animals
Wheat Rice Maize (corn) Potatoes Sweet potatoes Manioc Sugarcane Sugar beet Common beans Soy beans Barley Sorghum Coconuts bananas
Chickens Cattle Sheep Ducks Pigs Goats Buffalo camels
Good words to know
Forage: food grown for animals – alfalfa, sorghum, grasses
Rangeland: provides food for grazing, w/o plowing or planting
Pasture: plowed, planted and harvested for forage for animals
37 % of the Earth’s land area is agricultural land.
11% is used for crops – the rest is pastureland.
Pastureland : cultivated or wild forage crops and open land used for grazing.
United Nations Food and Agricultural Organization (FAO) states: ¾ of Earth’s land surface is unsuitable for growing rain-fed crops (w/o irrigation) 3.5% of the Earth’s surface is suitable for agriculture w/o any physical constraints (More inputs necessary, ie: fertilizer)
How is the Earth used?
In the US, Europe and Japan: Land is being
withdrawn from Agriculture. Productivity is higher than demand.
In these areas they rely on Agricultural Intensification to keep a high output on shrinking farmland
In developing worlds: land is being converted to agriculture. This also requires Agricultural Intensification.
Agricultural Intensification: fertilizers, irrigation, GM seed – High inputs
CO2 + H2O + sunlight → (CH2O)n + O2
Plants convert CO2 and water into plant tissue. This is the foundation of agricultural productivity.
We need to understand the roles of water and nitrogen (N).
We need to understand photosynthesis as a key input
Drought id the biggest limit on agricultural
productivity – plants need an enormous amount of water.
Plants use the energy from the sun to convert CO2 and water into carbohydrates. The ratio of water to CO2 is not equal. It is 400 to 1.
98% of the plants water travels upward through the roots and evaporates – exiting the leaf as water vapor through the stomata TRANSPIRATION
Water
Principle reason for transpiration is to allow
uptake of CO2 from the atmosphere. Water diffuses out of the plants leaves into the
surrounding atmosphere. (100% humidity in plant; 50% humidity in atmosphere – higher conc. To lower conc.)
CO2 diffuses into the plant.
CO2 diffusion is at a lower rate due to the conc. Of CO2 in atmosphere is .037% and zero in the plant
Transpiration
Stomata open to promote gas exchange when water
is plentiful, and constrict or close when water is scarce
The diffusional relationship between water and CO2, explains why drought is the major factor limiting
agricultural yields worldwide
Another critical resource for photosynthesis. Nitrogen is a limiting factor. It is an essential component of proteins,
especially the enzyme ribulose-biphosphate-carboxylase-oxygenase (RUBISCO)
This enzyme catalyzes the incorporation of CO2 into an organic molecule.
(RUBISCO is thought to be the most abundant protein on Earth – leaves are typically 2% Nitrogen- by dry weight)
Nitrogen
Fertilizer
Prior to WWI, main source of nitrogen fertilizer was manure
In S. America, nitrogen was mined; as saltpeter – through WWI
US gov’t allowed the acquisition of Guano Islands
1908 – German Chemist – Fritz Haber In an effort to create
munitions, created nitrogen fertilizer
Increasing Yields
Compared to undisturbed ecosystems (self maintained, nutrients cycle) agricultural, harvests crops – which removes material from the system permanently.
Farmers NEED to add nutrients and water to increase yields
Crops require 20 chemical elements Macronutrients: S, P, Mg, Ca, K, N, O, C, H Micronutrients: Cu, Zn, Mn, Fe, Molybdenum,
rarer metals Older soil is more likely to lack trace elements
because of leaching by water
Required Nutrients
Total output per unit of land Due to intensification
More technology inputs per acre Irrigation Synthetic fertilizers Pesticides and herbicides GM seeds
Higher yielding crops Larger portion of physical structure is devoted to
producing biomass. Growing deep root systems Plants with more seeds
Productivity
Green Revolution
A program established in the 1940’s
Distribution of high-yield crops varieties, synthetic fertilizers, irrigation techniques and pesticides to farmers in Asia and Latin America.
Helped to increase world food production at a pace greater than population growth.
1. Try to stop ecological succession and keep the agro-ecosystem in an early successional state
2. Monoculture: Large areas planted with a single species (entire crop vulnerable to disease, depletes soil of specific chemicals)
3. Crops are planted in neat rows – no hiding from pests or blending in
4. Farming greatly simplifies biological diversity & food chains
5. Plowing is unlike any natural soil disturbance – increases erosion and decreases organic matter
6. Genetic modification of crops?? What will this do?
Six Ways Agro-ecosystems Differ from Natural Ecosystems
Types of agriculture
Mechanized Agriculture: Production is
determined and limited by economic demand – NOT by resources
(land, water and fuel)
Old time farming. Supply and demand
Resource Based Agriculture
Production limited by environmental sustainability and available resources
Economic demand exceeds production Based on
biotechnology and conservation of land, water and energy
Organic Farming
Off shoot of Resource based farming
More like natural ecosystem
Minimizes negative environmental impact
Food does not contain artificial compounds
12,000 farmers in US - growing 12% per year
Insects, mice, rats, weeds, fungi, bacteria and
viruses Natural control : salt, sulfur and arsenic Synthetic pesticides are more effective:
1st pesticides: aldrin, dieldrin, heptachlor – human health effects – no longer used in US
DDT – Caused thin egg shells in predatory birds. – no longer used in US
Now: target specific pesticides Many pests are resistant
Combating Pests
Aquaculture
The farming of food in aquatic habitats Carp, tilapia, oyster, shrimp US – crayfish, salmon, trout and catfish China has been doing this – traced back to 475
BC
Mariculture The farming of ocean fish
Aquaculture
Undernourishment – lack of sufficient calories in available food. Manifested in famines that are fast acting (lack of food supply)
Problems with undernourishment: Marasmus: progressive emaciation due to lack of
protein & calories Kwashiorkor: lack of sufficient protein in infants –
failure of neural development Chronic hunger: enough food to stay alive, but not
enough to live a productive & satisfactory life
How we starve
Malnourishment – lack of specific chemical
components of foods ie: proteins, vitamins, etc. - Long term
(Eating, but not eating foods with enough nutrition)
How we starve
Africa – the continent with the most acute food
shortages due to weather & strife Food distribution fails because:
Poor cannot pay for food and/or delivery Transportation is lacking and too expensive Food is withheld for political & military purposes
Food aid is a short term answer
Must solve the problem of food distribution and increase local production ie: long term sustainable agriculture - locally
Food Aid
Organic agriculture introduced 10,000 yrs.
Ago. 18th & 19th centuries (industrial revolution)-
shift to mechanized or demand based agriculture
20th century- return to resource based agriculture
Today – growing interest in organic agriculture & use of genetically engineered crops
History of Agriculture
1. The Green Revolution- Programs that have led to the development of
new strains of crops with higher yields, better resistance to disease or better ability to grow under poor conditions- Ex: hybridized rice (increased yield)- Maize (disease resistant)
2. Improved Irrigationexpensive and found in developed
countries
Increasing the Yield per Acre
Genetically Modified Crops are modified by
genetic engineers to produce higher crop yields and increase resistance to drought, cold, heat, toxins, plant pests and disease.
Genetically Modified Food