Lecture 8 - Ecology of Ancient and Modern Food Production

quaternary period

quaternary period

last 2.68 million years where there was an ice age with alternating glacial and interglacial periods

when did humans emerge?

2 million years ago

Holocene epoch

an interglacial agricultural period that took place the last 10k years

ancestral human diet

opportunistic and unreliable because the default state for humans was to be hungry to the point of starvation

what constraints do humans have because we arent adapted for leaf feeding/folivory?

the plant foods we eat have to be of higher quality and less defended like fruits, seeds and tubers

when did agriculture arise?

when humans came to the Americas

what makes fruits good food?

they are attractive, tasty, sweet, and colorful because they have evolved for dispersal in plants because they get digested and defecated out of the animal and dispersal of seeds is a product of that

what is a reason that plants are nutritious?

they are initially heterotrophic before they become autotrophic

what makes seeds and tubers good?

plants are initially heterotrophic so it has the necessary carbs and energy reserve for a plant to start to grow and expand its leaves on it own so it becomes autotrophic via photosynthesis (built in set of energy storage)

what are tubers?

energy storage organs below ground that are sequestered and stored for future generations and seasons so they get digged up and eaten after a certain period of time

what are the key cultural innovations for human agriculture having occurred independently?

humans storing seeds and waiting for the next growing season to plant and cultivate the produce

grasses

wheat, rice, maize and barley

key evolutionary innovations to the domestication of grasses

non-shattering seed heads (easier for humans to grab and store) and amylase evolution

seeds prior to domestication

would be disturbed or shattered when lightly touched

legumes

beans, lentils, chickpeas, etc

fruits

tomatoes, squash, etc

ancient technological advances

• fishing by net

• irrigation channels

• domestication of cattle, sheep, poultry and evolution of lactose tolerance

• plow replaced digging sticks

• crop rotation and draft animals

• shift from nomad to sedentary life styles with the rise of cities

• exchange of crops, animals and tech

what are plant ranges of tolerance limited by?

temperature, water, nitrogen, phosphorus and potassium

limitations of intrinsic growth performance in crops

• limited areas suitable for growth

• edaphic factors

• soil exhaustion, insect buildup, disease

edaphic factors

soil moisture and fertility

Janzen-Connell effect

proposes that specialist natural enemies like herbivores and pathogens tend to accumulate near parent plants and can limit recruitment and growth of their own species’ offspring nearby

• promotes species diversity by reduction of competition, easier coexistence of different species in one community

issue with contemporary agriculture

in the 50s to 60s there was a population boom causing famine to occur tremendously because there was not enough resources to support the population at this rapid speed of growth

John Bennet Lawes (Rothamsted)

developed chemical fertilizers by using different crops and fertilizers at different concentrations to determine which concentration yielded the most biomass/agricultural output

what was known when repeated crop harvests were done?

they would exhaust soils so the crop yield would decline over time because nutrient were removed rather than recycled

how were soils amended after exhaustion?

by adding animal dung or whole animals to the soil because of their NPK contents acting as a fertilizer, organic matter also improved texture and water retaining capacity

what did lawes discover?

that most plants will have better growth responses if we supplement them with nitrate or ammonia (especially grasses)

Haber-Bosch process

using natural gas, atmospheric nitrogen and a catalyst under lost of pressure can generate ammonia and use it as a fertilizer (industrialized chemical fertilizer

corn based products

heavily dependent on nitrogen as a fertilizer for growth

atcama desert

mining town where nitrate and high nitrogen are accessible naturally so due to the Haber-Bosch process the town was abandoned because the chemical fertilizer was better

what else was the haber-bosch process key in producing?

key in producing explosives and munitions

irrigation canals

brings water from wetter areas to drier areas

fertilizer

added to soils to bring them nutrients and make them more suitable for growth

industrial chemistry

makes fertilizer cheaper

green revolution

used artificial selection and hybridization to evolve high-yielding dwarf crop varieties (didn’t grow as tall + didn’t sense neighbors so no competition between them), excess energy is put into seed yield

• Norman Borlaug brought this to light to aid famines in India

Yuan Longping

developer of high yield rice by testing and rejecting Lysenkoism with experiment using grafting of sweet potatoes

Lysenkoism

the inheritance of acquired characteristics, used to be the dominant dogma in communist countries in the USSR and China

Longpin’s key insight that led him to refute Lysenkoism

rice is normally self pollinating so hard to cross and make better varieties but if you find male sterile plants and they have some mutation that makes them not produce the male gamete you have a female plant that is a recipient in a cross allowing you to make hybrid varieties

plant allocations favored in nature

• grow tall to compete for light and enhance pollination and seed dispersal

• extensive roots to capture scarce water and nutrients

• make physical and chemical defenses against herbivores and fungi

changes under modern agriculture

• competition can now be prevented by mechanized cultivation and herbicides will other selection is reduced

• water and nutrients can be supplied by irrigation and fertilizer

• they can be protected by insecticides and fungicides

what is the downside of using agricultural fertilizer?

you need an energy rich supply that can be limited dependent on the fossil fuels needed for its creation, distribution and application

annual wheat

not producing a giant root system that’s fighting bacteria so that energy can be put into yield so maybe it’s more sustainable because you don’t need irrigation or NPK

benefits of the green revolution

yields went up so the famines were averted, HVY productivity likely saved other habitats from agricultural conversion

disadvantages of the green revolution

HVY are needy so they probably interact with climate change cause they need fossil fuels and crops seem to be plateauing in yields

mechanized agriculture

better at maximizing yield but it requires energy subsidies (we need to input fossil fuel based fertilized to run the equipment in order for it to work)

economic and political implications

• cost of food tied to the cost of petroleum and electricity

• China and India subsidize the costs of N fertilizer to farmers

• increasing the food supply requires burning more fuel and clearing more land