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When was agriculture doing a good job of producing enough to meet a growing demand?
- During the later half of the 20th century
- Attributed to scientific advances and technology
- New plant variets, fertilizers, pesticides, intensive infrastructure for irrigation
What are some challenges ag has experienced in the first years of the 21st century?
- World population continues to grow
- New technologies and techniques have overdrawn resources such as soil, water and natural genetic diversity
- Dependence on fossil fuels, responsibilities shift away from farmers and farm workers
Some threats to ag not created by conventional farming?
- emergence of new ag diseases (mad cow, Nipah virus)
- climate change
Two key goals of conventional agriculture?
- Maximize profit
- Mazimize production
Purpose of intensive tillage
- loosen the soil structure to allow better drainage, faster root growth, aeration and easier seed sowing
- fields are typically plowed several times/year, leaving soil free of cover for extended periods
Drawbacks of intensive cultivation
- soil's organic matter reduces (result of accelerated decomposition and lack of cover)
- soil compacted by heavy machinery
- loss of organic matter reduces fertility and degrades soil structure
What modern farming practice is a natural outgrowth of an industrialized approach to agriculture?
- Labor inputs are minimized, technology inputs maximized to increase production
What practice is one of the key reasons for large increases in yields during the second half of the 20th century?
- Synthetic chemical fertilizers
- Rapid expansion after WWII in the US
Worldwide, what are the trends in use of fertilizer
- Increased 10-fold between 1950 and 1992
- Increase moderated since
- 2002, total world consumption estimated at 141.6 million metric tons
excessive growth of oxygen-depleting plant and algal life
Benefits of synthetic fertilizer
- relatively low costs
- can be applied easily and uniformly to crops
- supply plants with most esstential plant nutrients
drawbacks to synthetic fertilizer use
- farmers can ignore long-term soil fertility and processes by which it's maintained
- mineral components easily leached out of soil and ends up in streams, lakes, rivers
- farmers have no control over cost since it's tied to petroleum, fossil fuels, mined mineral deposits
What is a limiting factor for food production in many parts of the world?
- Adequate water supply
- To increase yields, water comes from underground aquifers, reservoirs, diverted rivers
Only 18% of the world's crop land is irrigated. How much of the world food supply does it produce?
- Agriculture accounts for 70% of world water use
After WWII, these were promoted as the new, scientific weapon in humankind's war against plant pests and pathogens
Chemical pesticides and weed control
What is the pesticide treadmill?
- pesticides lower pest populations in the short term, but also lower numbers of pests' predators, allowing for quicker rebounds and more pesticides
- also increased resistance
What are the U.S. trends in pesticide use?
- Remains at twice the level it was in 1962
- According to Pimentel's (one hand clapping) crop losses stayed fairly constant despite increasing pesticide use
Precursor to GMOs
- Hybrid seeds - combine characters of two or more plant strains
- Can be much more productive than nonhybrid varieties but require optimal conditions (nonorganic fertilizer, pesiticide treatments)
- Cannot produce seeds with same genome as parents, which makes farmers dependent on commercial seed producers
customized production of plant and animal varieties by splicing genes from a variety of organisms into a target genome creates
transgenic, genetically modified organisms, genetically engineered
Worldwide trends in genetically engineered crops?
- Between 1996 and 2003, increased almost 40-fold, from 1.7 million ha to 67.7 million ha
- 55% of world's soybean crop, 21% of cotton crop was transgenic in 2003
Potential advantages to GMOs
- reduced use of pesticide and irrigation
- allowance of ag on soils too saline for normal crops
- increasing nutritional value of some crops
Possible drawbacks to GMOs
- migration of modified genes into other populations (wild and domestic)
- diminishment of biodiversity
- increased dependence of farmers on those who own the patents
- Confined animal feeding operations
- Essentially, the factory farming of animals
Impacts of CAFOs on the environment
- large amounts of waste treated in anaerobic lagoons (nitrates into surface streams and groundwater, ammonia into atmosphere)
- smaller, traditional farms would recycle nitrogen within their own systems, fertilizing crop fields with manure
Worldwide diets are trending towards higher meat and animal product consumption. What does the increased demand mean for agriculture?
- Industrialized methods of animal food production become more profitable and more widespread
- replaces more mixed crop-livestock and pastoral systems
Worldwide grain production per capita peaked when?
Why have per capital production of grains trended downward since 1984?
Reduced annual yield increases combined with continued population growth
Some examples of externalized costs due to conventional agriculture
soil, water, genetic diversity overdrawn and degraded
Consequences of externalized costs of conventional agriculture?
Because their consquences can be temporarily ignored or absorbed by society as a whole, they are excluded from cost-benefit calculations
According to the FAO, how much land is lost to soil degradation each year?
- Between 5 and 7 million ha
- Other estimates are as high as 10 million
Forms of soil degradation
- salting, waterlogging, compaction, contamination by pesticides, decline in the quality of soil structure, loss of fertility, erosion by wind and water
- erosion is most wide-spread (world-wide, 25 million tons of topsoid washed away annually)
Soil is created at the rate of about 1 ton per ha per year. How much is lost to wind and water erosion per year?
- 5-10 tons/ha in Africa, South America and North America
- 30 tons/ha in Asia
Most valuable soil component
What is a direct cause of much of the water erosion of agricultural soil?
Can fertilizers rebuild soil fertility and restore soil health?
- They temporarily replace lost nutrients
What needs to happen for agriculture to become sustainable
- it needs to reverse the process of soil degradation
- supply of soil is finite and natural processes can't renew or restore as fast as it's degraded
What happens to more than half the water applied to crops?
It's never taken up by the plants it's intended for, so it either evaporates or drains out of fields
What are some ways to shift agriculture towards conservation of water?
- watering with drip irrigation systems
- shifting production of water-intensive crops such as rice away from regions with limited water supplies
How many liters of water to grow 500 calories of potatoes and 500 calories of grain-fed beef?
- 89 liters - potatoes
- 4902 liters - beef (55 times more)
On average, producing one 1kg of animal protein requires how much more water than grain protein?
100 times more
How do CAFOs contribute to water overuse?
- cooling animals
- flushing wastes
- consumption of water by animal
- grow biomass to feed animals
- animal-derived food requires at least twice as much water to produce as plant-derived
What are some agricultural pollutants of water?
pesticides, herbicides, other agrochemicals, fertilizer, animal wastes, salts
Indirect spread of pesticide damage
Fish-eating raptors may eat pesticide-laden fish, reducing reproductive capacity
- low oxygen
- sustained hypoxic conditions can kill fish and bottom-dwelling organisms (Gulf of Mexico's "Dead Zone")
- nitrogen and phosphorus from animal waste and inorganic fertilizer create these dead zones near rive mouths
- more than 50 dead zones exist seasonally around the world
Conventional farm practices rely on a large amount of external inputs, such as machinery, pesticides, processed feed and antibiotics, hybrid and transgenic seeds. How does this affect farm profits?
- The longer these practices are used, the more the farm relies on these external inputs.
- Farmers are vulnerable to supply shortages, market fluctuations and price increases
Has genetic diversity increased or decreased during the last 100 years?
- 75% of genetic diversity in crop plants in 1900 has been lost
- As many as two domesticated animal breeds are being lost each week worldwide
How many varieties of corn make up the majority of the world's corn crop?
- 99% of turkeys raised in the U.S. belong to a single breed
Vulnerabilities of genetic uniformity for crop plants
- attack by pests and pathogens that acquire resistance to pesticides and the plants' own defensive compounds
- climate changes and other environmental factors
- yearly, pests and pathogens destroy an estimated 30-40% of potential yield
What percentage of the world's population is expected to live in urban and industrial areas by 2030?
Percentage of the U.S. population that lives on farms:
- below 2%
- 2 million farms in the U.S. (6.5 million in 1920)
- More people in the world earn their money from nonagricultural occupations than there are people who grow food
How is the farmers' share of the consumer food dollar trending?
- Lower - in 1910, slightly less than 50% went to marketing, while nearly 38% went to farmers
- By 1997, marketers earned more than 70% while farmers earned roughly 8%
- Purchased inputs are also gaining a share of the food dollar, but not as dramatically (maybe 12% in 1910, and 18% in 1997)
With less incentive to stay on the family farm, what trends are occuring?
- Large firms purchasing smaller neighboring farmers' lands
- Sale of farm land as urban land (residential, commercial)
What dubious accomplishment was reached at the beginning of the 21st century?
- The number of overweight people (about 1.1 billion) grew roughly equal to the number of underweight people
- Unequal distribution of food is at least as serious a problem as threats to global food production
What seems to be the trend in agriculture for developing countries?
- grow food mainly for export to developed nations
- use of external inputs purchased from developed nations
- concentrated wealth (landowners retain profts)
- less affluent landowners are displaced as large-scale producers expand
Between 1973 and 2003, the world's population increased by 61%. How much did worldwide meat production increase?
- By more than 133%
- Meat produced per person on the rise since data collection began in 1961, was higher than 40 kg/person in 2004
the condtion of being able to harvest biomass from a system in perpetuity because the ability of the system to renew itself or be renewed is not compromised
Agriculture needs to meet two goals in the future
- feed growing human population
- be sustainable
the application of ecological concepts and principles to the design and management of sustainable food systems
ecological methods and principles are essential for determining what two things
- 1. if a particular agricultural practice, input, or management decision is sustainable
- 2. the ecological basis for the functioning of the chosen managment strategy over the long term
- a site or integrated region of agricultural production understood as an ecosystem
- a farm
a functional system of complementary relations between living organisms and their environment
basic structural components of ecosystems
- biotic factors (living organisms that interact in the environment)
- abiotic factors (nonliving physical and chemical components of the environment - soil, light, moisture, temperature)
individual organism and the ecosystem
- look at how a single individual of a species performs in response to factors of the environment
- its degree of tolerance to stresses determine where it will live
groups of indviduals of the same species/population and the ecosystem
- determine factors that control population size and growth
- the capacity of the environment to support a population over time
populations of diffferent species/community and the ecosystem
- how interactions of organisms affect the distribution and abundance of the different species that make up a particular community
- competition between plants in a cropping system, predation of aphids by lady beetles
Two factors that influence a community's development
- 1. adaptations of its component species to the gradients of abiotic factors that occur in its environment
- 2. a result of interactions between populations of these species
the number of species that occur in a community
- the species with the greatest impact on biotic and abiotic components of the community
- can be a result of an organism's relative abundance, its size, its ecological role or a combo of factors
terrestrial communities are often characterized by
- the structure of their vegetation
- determined by the form of dominant plant species, as well as the form and abundance of other plant species and their spacing
the structure of feeding relationships that meets every species in a community's nutritive needs
Why are plants known as producers?
- they capture solar energy and convert it into stored chemical energy (biomass)
- biomass serves as food for other species
physiologically, plants are classified as autotrophs why?
they satisfy their energy needs without preying on other organisms
their nutritive needs are met by consuming other organisms
consumers of a community (ecosystem wise)
- parasites (consume from host but generally do not kill it)
- parasitoids (insects whose larvae live within and consume their host, usually another insect)
- over time, species diversity, dominance structure, vegetative structure, and trophic structure remain fairly stable
- ecologists disagree on whether stability should be considered an inherent characteristic of communities or ecosystems
- dynamic processes occuring within ecosystems
- movement of matter and energy, interactions and relationships of organisms and materials
two fundamental processes in any ecosystem
- flow of energy among its parts
- cycling of nutrients
how can you measure the amount of energy that plants have brought into an ecosystem
- by determining the standing crop, or biomass of the plants in the system
- this is a measurement of a specific point in time
gross primary productivity
- a measurment of the rate of the conversion of solar energy to biomass
- usually in terms of kilocalories per square meter per year
net primary productivity
gross primary productivity minus the energy plants use to maintain themselves
Why is only a small percentage of biomass at one trophic level converted into biomass at the next trophic level?
- a large amount of energy is expended in maintaining the organisms at each level
- as much as 90% of the consumed energy
biomass that isn't consumed or fully digested
in the form of dead organisms and fecal matter, this is eventually broken down by detrivores and decomposers
what happens in the decomposition process
- it releases, in the form of heat, much of the energy that went into creating the biomass
- the remaining biomass is returned to the soil as organic matter
nearly all the energy that enters an ecosystem is eventually dissipated as what
How do nutrients flow through an ecosystme?
- They move in cycles
- through the biotic components of an ecosystem to abiotic components and back to biotic
- both abiotic and biotic components of the ecosystem are involved
- as a whole, biogeochemical cycles are comples and interconnected
- many occur at a global level that transcends individual ecosystems
Most important nutrients cycled through ecosystems
- Carbon (C)
- Nitrogen (N)
- Oxygen (O)
- Phosphorus (P)
- Sulfur (S)
- minus water, each of these is known as a macronutrient
the atmosphere functions as the primary abiotic reservoir for which nutrients?
- carbon, oxygen and nitrogen
- these cycles take on a global character
soil serves as the bain abiotic reservoir for which nutrients?
- less mobile elements such as phosphorus, sulfur, potassium, calcium, most trace elements
- nutrients are taken up by plant roots, stored in biomass and eventually returned to the soil within the same ecosystem by decomposers
The cycling of phosphorus between organisms and soil tends to be localized in ecosystems, minus two exceptions What are they?
- 1. phosphates may leach out in ground water if they are not absorbed or bound
- 2. phosphates adhering to soil particles may be removed by erosion
- in both cases, phosphates leave the ecosystem and end up in the oceans
- needed in very small quantities, but still important
- Iron (Fe), Magnesium (Mg), Cobalt (Co), boron (B), Zinc (Zn), molybdenum (Mo)
when the adaptations of two species are very similar and resoures are insufficient to maintain populations of both
resources are shared or partitioned between species
- the recovery of a system following a disturbance
- end point of succession is the climax stage
overall stability combined with dynamic change
why is dynamic equilibrium so important to agriculture?
it permits the establishment of an ecological balance, functioning on the basis of sustained resource use, which can be maintained indefinitely despite ongoing and regular change in the form of harvest, soil cultivation and replanting
Energy flow in agroecosystems
- inputs derived from primarily human sources (often not self-sustaining)
- considerable energy directed out of the system at the time of harvest (v. stored in biomass)
nutrient cycling in agroecosystems
- recycling of nutrients is minimal
- quantities lost with harvest or through leaching, erosion
- some farmers rely heavily on petroleum-based nutrient inputs to replace losses
population regulating mechanisms in agroecosystems
- humans control the population sizes through seed or control agents, so rarely are plants and animal populations self-regulating
- biological diversity is reduced and trophic structures become simplified
- not so much, compared to natural ecosystems
- harvest output focus upsets equilibrium
- need outside interference - human labor and inputs - to maintain