1. Land Use Part II: Agricultural Issues

2. Pesticides – Agricultural Chemicals
Industrial agriculture relies on pesticides to produce their crops.
A pesticide
Is a poison used to destroy pests, such as insects, rodents, or weeds
Pesticides can also harm:
Beneficial plants and insects, wildlife and people

3. Pesticide Resistance Pesticide Resistance
Over time, spraying large amounts of pesticide to get rid of pests usually makes the pest problem worse.
Pest populations may evolve resistance
Most surviving individuals have characteristics that allowed them to tolerate the pesticide.
Survivors pass on genetic characteristics for tolerance.
Subsequent pesticide applications become less effective.
More than 500 species of insects have developed resistance to pesticides since the 1940s.

4. Persistence Persistence
Does not break down easily or quickly in the environment.
Do not break down into harmless chemicals, and they accumulate in the water and soil.
Some pesticides have been banned in the United States for decades but can still be detected in the environment.
Persistent pesticides become attached to small soil particles and are easily moved by wind or water.
Persistent pesticides have been discovered in polar ice and are present in detectable amounts in the bodies of animals, including humans, throughout the world.

5. Agricultural Chemical Use
Herbicides
Are used to control unwanted plants.
About 60% of pesticides used in U.S. are herbicides.
Weeds compete with crops for soil nutrients.
Traditional weed control methods are expensive in terms of time and energy.
Several major types of herbicides are in current use.
Auxins
Synthetic plant growth regulators mimic natural growth regulators
Photosynthetic disruptors
Enzyme inhibitors

6. Some herbicides are toxic to all plants (nonselective), and some are selective as to the plant species they affect.
Atrazine is often used to control broad-leaf and grassy weeds.
Glyphosate (Roundup) is a broad-spectrum, nonselective, systemic herbicide used to control plants.
Fungicides are used to protect agricultural crops from spoilage, to prevent the spread of disease, and to protect seeds from rotting in the ground before they can germinate.
Methylmercury is extremely toxic to humans.
In some parts of the world, governments pay a bounty to people who kill rats because they can destroy agricultural crops.
Rodents also carry diseases harmful to humans.
Rodenticides must be used with great care to prevent poisoning nontarget organisms.

7. Problems with Pesticide Use
Bioaccumulation
is the process of accumulating higher and higher amounts of material within an organism’s body.
Many persistent pesticides are fat soluble and build up in fat tissues.
Biomagnification
is the process of acquiring increasing levels of a substance in bodies of higher trophic-level organisms.
DDT, mercury, and PCBs are all known to accumulate in ecosystems.
DDT was banned in the U.S. in the early 1970s.

10. Problems with Pesticide Use
Pesticide resistance is a problem associated with the widespread use of pesticides.
Most pesticides are not species-specific, and kill beneficial species as well as pest species.
Many kill predator and parasitic insects that normally control pest insects.
Insecticides may change the population structure of the species present so that a species not previously a problem may become a serious pest.
Pesticides are designed to kill organisms, so they may also be dangerous to humans.
Short-term and long-term health effects to persons applying pesticides and the public that consumes pesticide residues in food are also concerns.

11. Acute poisoning during application sometimes occurs when farmers cannot read caution labels on packaging or do not have access to protective gear.
The WHO estimates between 1 million and 5 million acute pesticide poisonings occur annually, resulting in 20,000 deaths.
For most people, the most critical health problem is inadvertent exposure to small quantities.
Farmers who were occupationally exposed to pesticides over many years show that they have higher levels of certain kinds of cancers than the general public.
Chronic minute exposures to pesticide residues in food or through contaminated environments are also of concern.

12. Why Are Pesticides So Widely Used ?
Food Production
Worldwide, pests destroy 35% of crops.
This represents an annual loss in U.S. of $18.2 billion.
Economic Concerns
Pesticides increase yields and profits.
Health Reasons
Insecticides curtail many diseases.

13. Problems with Pesticide Use
A perfect pesticide would have the following characteristics:
Inexpensive
Only affect target organisms
Short half-life
Break down into harmless materials
Newer pesticides have fewer drawbacks than early pesticides, but none are devoid of problems.

14. Rachel Carson – Silent Spring

15. How is Arable Land Lost? Land Degradation ha stands for hectare
Which is 10,000 square meters or about 2 and a half acres.
3 million ha of cropland ruined annually via erosion
4 million ha transformed into deserts
8 million ha converted to non-agricultural uses
Converting arable land with subdivisions
Over the past 50 years, 1.9 billion ha of agricultural land has been degraded.

16. Arable Land Unevenly Distributed
North America and Europe are particularly well suited to growing while some other parts of the world lack suitable soil, topography and water.
The amount of available cropland is shrinking.
Exceptions are South America and Oceania, where forests are being converted to farms
Gains in agricultural production have come from increased fertilization, pesticides and irrigation rather than more land.

17. Land Degradation
Definitions of degradation are based on both biological productivity and expectations of what land should be like.
Generally, land is considered degraded when
Soil is impoverished or eroded
Run-off is contaminated
Biodiversity is diminished.
Water and wind are the driving forces for vast majority of soil degradation.

18. Erosion
Erosion is a natural process, resulting in redistribution of the products of geologic weathering, and is part of both soil formation and soil loss.
Worldwide, erosion reduces crop production by equivalent of 1% of world cropland per year.
Erosion results in sediment loading of rivers and lakes, siltation of reservoirs, and smothering of wetlands and coral reefs.
Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land.

19. Desertification Conversion of productive lands to desert
threatens 1/3 of the earth’s surface and 1 billion people
Rangelands and pastures are highly susceptible (overgrazing, soil degradation).
Africa and China are of particular concern.
Rapid population growth and poverty create unsustainable pressures.
Removal of trees for fodder and firewood triggers climate change that spreads desertification.

20. Soil Degradation in the U.S.

21. Genetic Engineering and Agriculture
Removes DNA from one organism and splices it into the chromosomes of another.
Produces genetically modified organisms (GMOs) with new traits.
Can produce crops with pest-resistance and wider tolerance levels to frost, drought, low nutrient soils, salty soils, etc.
Can improve protein or vitamin content of crop
Can incorporate oral vaccines into foods such as bananas for use in developing nations
Animals can be modified to grow faster or produce pharmaceuticals in their milk.
It differs from traditional breeding methods in that desirable genes from any organism can be used, not just those from the species of plant or animal being improved
Can also be called transgenic organisms

24. Examples of GMO’s
Biotechnologists have recently created plants containing genes for endogenous insecticides.
A gene from the bacterium Bacillus thuringiensis (Bt) makes toxins that are lethal to butterflies and beetles. These genes have been transferred into corn, potatoes and cotton. Reduces pesticide use and increases yield.
Concern has arisen over several points.
Spread of genes into wild populations leading to resistance in pests
Effect on nontarget species
Transgenic crops can be engineered to tolerate high levels of pesticides.
Roundup Ready and Liberty Link are two most popular. Crops can grow in the presence of the pesticides (called Roundup and Liberty) while weeds within the field are killed.

25. Issue with GMOs Concerns about GMO seed or pollen spreading in wild
Produce superweeds resistant to pesticides.
Native biodiversity may be reduced.
Novel toxins might be created
Cartagena Protocol on Biosafety regulates these concerns
US is an active observer
Knowing what foods have/are GMOs
Determined to be safe for human consumption
GMOs are not currently labeled
FDA finds it would be counterproductive and expensive to label
You are already eating GMOs as 60% of processed food in the U.S. contains GMOs.
Technology may only be available to the rich, making family farms uncompetitive and driving poor nations further into poverty.

26. Environmental and consumer groups have campaigned against GMO’s
European nations have bans on GMOs.
Worry that genetically modified animals will escape captivity and outcompete their wild relatives.
Salmon with added growth hormone gene grow 7X faster than their wild counterparts.

27. Domestication and Genetic Diversity
Domestication of crops and livestock causes a loss of genetic diversity
Farmer selects and propagates animals with desirable agricultural characteristics
Many high yielding crops are genetically uniform
High likelihood that bacteria, fungi, viruses, etc. will attack and destroy entire crop
Increasing Livestock Yields
Hormone supplements
US and Canada do this
Europe does not citing human health concerns

28. Concentrated animal feeding operations
In North America animals are fattened on grain in feedlots
Local air and water pollution caused by untreated waste
Waste can contaminate soil and food.
Recent spinach contamination
High density of animals requires constant use of antibiotics, leading to antibiotic resistance in microbes.
40% of antibiotics produced in US are used in livestock operations
Problems with increased bacteria resistance

29. This American Clip – 5:27

30. Seafood Aquaculture supplies food, but it
uses wild populations to stock and feed captive populations
destroys mangrove forests and wetlands used as nurseries for all marine species
allows the spread of disease
releases large quantities of feces, antibiotics and other pollutants

32. The Problems With Monocultures
Biodiversity loss
Loss of habitat through conversion of grasslands and forests along with wetland draining
Fish kills from agricultural runoff
Extermination of predators
Loss of genetic diversity due to monocultures
Genetic pollution from bioengineered or selectively bred organisms that “escape” and interbreed with native species
Spread of diseases from agroecosystems to natural ecosystems
Water
Aquifer depletion
Increased runoff, due to land clearing and plowing
Sediment pollution from runoff
Fish kills from pesticide runoff
Surface and groundwater pollution from pesticides, antibiotics, and fertilizers
Over-fertilization of lakes, rivers, and coastal ocean from fertilizers, livestock wastes, and food processing wastes